U.S. patent application number 11/248541 was filed with the patent office on 2006-03-30 for synthesis, compositions and methods for the measurement of the concentration of stable-isotope labeled compounds in life forms and life form excretory products.
This patent application is currently assigned to BioPhysics Assay Laboratory, Inc.. Invention is credited to Ernest V. Groman, Christopher P. Reinhardt.
Application Number | 20060067881 11/248541 |
Document ID | / |
Family ID | 23015415 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060067881 |
Kind Code |
A1 |
Groman; Ernest V. ; et
al. |
March 30, 2006 |
Synthesis, compositions and methods for the measurement of the
concentration of stable-isotope labeled compounds in life forms and
life form excretory products
Abstract
Stable isotope labeling and neutron activation to measure
biological functions are provided, as are the use and method of
adding a chemical monitor to correct for neutron flux to sample
vials prior to the addition of sample is presented, and the use of
stable isotopes as a chemical bar code for vials and other items.
Methods are provided also for measuring glomerular filtration rate
and glomerular sieving function in a subject, and for measuring
other physiological functions.
Inventors: |
Groman; Ernest V.;
(Brookline, MA) ; Reinhardt; Christopher P.;
(Worcester, MA) |
Correspondence
Address: |
Sonia K. Guterman;Lawson & Weitzen, LLP
Suite 345
88 Black Falcon Ave.
Boston
MA
02210-2481
US
|
Assignee: |
BioPhysics Assay Laboratory,
Inc.
|
Family ID: |
23015415 |
Appl. No.: |
11/248541 |
Filed: |
October 12, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10060652 |
Jan 30, 2002 |
|
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11248541 |
Oct 12, 2005 |
|
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60266647 |
Feb 5, 2001 |
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Current U.S.
Class: |
424/1.11 ;
424/9.2; 702/19 |
Current CPC
Class: |
A61K 51/0497 20130101;
A61K 51/065 20130101; A61K 47/60 20170801; A61K 33/242 20190101;
A61K 51/0493 20130101; A61K 41/009 20130101; A61K 51/1255 20130101;
A61K 33/244 20190101 |
Class at
Publication: |
424/001.11 ;
424/009.2; 702/019 |
International
Class: |
A61K 51/00 20060101
A61K051/00; A61K 49/00 20060101 A61K049/00; G06F 19/00 20060101
G06F019/00 |
Claims
1. A composition comprising a compound having a structure X-M,
wherein X is a chelator, M is an atom of a stable isotope of an
element having a nucleus capable of capturing a neutron and
subsequently emitting a photon, M is noncovalently bound to X, X
being at a concentration at least as great as that of M, the
composition having a counterion and a physiologically acceptable
buffer.
2. A composition according to claim 1, wherein M is selected from
the group consisting of: .sup.45Sc, .sup.50Cr, .sup.55Mn,
.sup.58Fe, .sup.59Co, .sup.63Cu, .sup.103Rh, .sup.13Cd, .sup.114Cd,
.sup.113In, .sup.115In, .sup.123Te, .sup.133Cs, .sup.139La,
.sup.141Pr, .sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.15Eu,
.sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb,
.sup.158Dy, .sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy,
.sup.164Dy, .sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf,
.sup.175Yb, .sup.165Ho, .sup.175Lu, .sup.176Lu, .sup.181Ta,
.sup.185Re, Re, .sup.190Ir, .sup.193Ir, .sup.196Hg, .sup.202Hg, and
.sup.197Au.
3. A composition according to claim 1, wherein the counterion is
meglumine (1-deoxy-1-methylamino-D-glucitol antimoniate).
4. A composition according to claim 1, wherein X is selected from
the group consisting of: diethylenetriaminepentaacetic acid (DTPA),
diethylenetriamine-pentamethylenephosphonic acid (DTPMP),
tetraazacyclododecanetetraacetic acid (DOTA) or a derivative of
DOTA, ethylene-diaminetetraacetic acid (EDTA),
tetraazacyclododecanetetrakis (methylene phosphonic acid) (DOTP),
hydroxypropyl tetraazacylododecanetriacetic acid (HP-DOPA),
diethylenetriaminetriacetic acid bismethylamide (DTPA-BMA), and
MS-325.
5. A composition according to claim 1, wherein the concentration of
X is between about 100 micromolar and about 1.5 molar.
6. A method of preparing a pharmaceutical composition of a compound
having a structure X-M, the method comprising: providing a solution
having X and M, wherein X is a chelator, and M is an atom of a
stable isotope of an element noncovalently bound to X and having a
nucleus capable of capturing a neutron and subsequently emitting a
photon, and the concentration of X is at least as great as that of
M, the solution being aqueous and having a physiologically
acceptable buffer; and sterilizing the solution.
7. A method according to claim 6, wherein M is selected from the
group consisting Of .sup.45Sc .sup.50Cr, 55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.103Rh, .sup.113Cd, .sup.114Cd,
.sup.113In, .sup.115In, .sup.123Te, .sup.133Cs, .sup.139La,
.sup.141Pr, .sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151Eu,
.sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb,
.sup.158Dy, .sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy,
.sup.164Dy, .sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf,
.sup.175Yb, .sup.165Ho, .sup.175Lu, .sup.176Lu, .sup.181Ta,
.sup.185Re, .sup.187Re, .sup.190Ir, .sup.193Ir, .sup.196Hg,
.sup.202Hg, and .sup.197Au.
8. A method for quantifying by neutron activation an amount of a
complex having a structure X-M, the method comprising: exposing
each of the X-M complex and a standard to a neutron source, wherein
X is a chelator and M is an atom of a stable isotope of an element
having a nucleus capable of capturing a neutron and subsequently
emitting a photon, and wherein the standard has a predetermined
quantity of M, the X-M and the standard being exposed to the
neutron source at the same time, such that M emits a photon after
capture of a neutron; detecting an emitted photon from each of X-M
and the standard; and comparing an amount of photonic emissions
from each of the X-M and the standard, thereby quantifying the
amount of the complex having the structure X-M.
9-22. (canceled)
23. A composition comprising at least one compound
.OMEGA..sub.i-X.sub.j-M.sub.k and a counterion, wherein: each
.OMEGA..sub.i is an organic compound having a molecular weight
greater than about 50; each X.sub.j is at least one chelator
covalently bound to each .OMEGA..sub.i; and each M.sub.k is
noncovalently bound to X and has a nucleus capable of capturing a
neutron and subsequently emitting a photon and is an atom of a
stable isotope of an element selected from the group consisting of
.sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu,
.sup.103Rh, .sup.113Cd, .sup.114Cd, .sup.113In, .sup.115In,
.sup.123 Te, .sup.133Cs, .sup.139La, .sup.141Pr, .sup.146Nd,
.sup.149Sm, .sup.152Sm, .sup.151Eu, .sup.153Eu, .sup.152Gd,
.sup.155Gd, .sup.157Gd, .sup.159Tb, .sup.158Dy, .sup.160Dy,
.sup.16Dy, .sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.168Yb,
.sup.169Tm, .sup.174Hf .sup.178Hf, .sup.175Yb, .sup.165Ho,
.sup.175Lu, .sup.176Lu, .sup.181Ta, .sup.185Re, .sup.187Re,
.sup.190Ir, .sup.193Ir, .sup.196Hg, .sup.202Hg, and .sup.197Au,
wherein each M.sub.k is distinct in identity; i, j, and k each
being a number from 1 to 8, wherein i is at least equal to k.
24. A composition comprising at least one compound
.OMEGA..sub.i-X.sub.j-Mk, at least one compound .PSI.-N, and a
cationic counterion, wherein: each .OMEGA. is an organic compound
having a molecular weight greater than about 50; each X is at least
one chelator covalently bound to .OMEGA. and noncovalently bound to
M; .PSI. is a chelator noncovalently bound to N; N is different
from M, and N and each M being, independently, an atom of a stable
isotope of an element selected from the group consisting of
.sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu,
.sup.103Rh, .sup.113Cd, .sup.114Cd, .sup.113In, .sup.115In,
.sup.123Te, .sup.133Cs, .sup.139La, .sup.141Pr, .sup.146Nd,
.sup.149Sm, .sup.152Sm, .sup.151Eu, .sup.153Eu, .sup.152Gd,
.sup.155Gd, .sup.157Gd, .sup.159Tb, .sup.158Dy, .sup.160Dy,
.sup.161Dy, .sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.168Yb,
.sup.169Tm, .sup.174Hf, .sup.178Hf .sup.175Yb, .sup.165Ho,
.sup.175Lu, .sup.176Lu, .sup.181Ta, .sup.185Re, .sup.187Re,
.sup.190Ir, .sup.193Ir, .sup.196Hg, .sup.202Hg, and .sup.197Au,
each M and N, independently, having a nucleus capable of capturing
a neutron and subsequently emitting a photon; and i, j and k are
independently each a number from 1 to about 8.
25. A composition comprising: a compound .OMEGA..sub.i-M and a
cationic counterion, wherein: each .OMEGA. is an organic compound
having a molecular weight greater than about 50, i being a number
from 1 to about 8; and M is an atom of a stable isotope of an
element selected from the group of elements consisting of .sup.36S,
.sup.74Se, .sup.79Br, .sup.81Br, .sup.107Ag, .sup.109Ag, .sup.127I,
.sup.197Au, .sup.190Pt, and .sup.196Hg, wherein M is covalently
bound to Q and has a nucleus capable of capturing of a neutron and
subsequently emitting a photon.
26. A composition according to claim 24, wherein the at least one
.OMEGA..sub.i-X-M.sub.i compound differs in molecular weight range
from the other compounds, the .OMEGA..sub.1-X-M.sub.i compounds
having the same net charge.
27. A composition according to claim 24, wherein the
.OMEGA..sub.i-X-M.sub.i compounds have different net charges and
about the same molecular weight.
28. A composition according to claim 24, wherein .OMEGA..sub.i is a
polymer.
29. A composition according to claim 28, wherein the polymer is
selected from the group consisting of a polysaccharide, a
polypeptide, and a polynucleotide.
30. A composition according to claim 29, wherein the polysaccharide
is a ficoll, a dextran, a pullulan, a starch, or a
hydroxyethylstarch.
31. A composition according to claim 29, wherein the polypeptide is
covalently attached to a polyethylene glycol polymer.
32. A composition according to claim 24, wherein the non-covalently
bound chelator is a bile acid compound.
33. A composition according to claim 32, wherein the bile acid
compound is selected from the group consisting of cholic acid,
cholic acid taurine, chenodeoxycholic, deoxycholic acid, homocholic
acid taurine, and lithocholic acid.
34. A composition according to claim 32, wherein the bile acid
compound is a synthetic derivative of a bile acid.
35. A composition according to claim 24, wherein the non-covalently
bound chelator is a drug or a drug metabolite.
36. A composition according to claim 35, wherein .OMEGA..sub.i is
selected from the group consisting of a hormone and a hormone
antagonist.
37. A composition according to claim 36, wherein .OMEGA..sub.i is a
steroid hormone.
38. A composition according to claim 24, wherein the non-covalently
bound chelator is selected from the group consisting of an
antibiotic, a tranquilizer, a vitamin, a narcotic, a cannabinoid, a
barbiturate, and an alkaloid.
39. A composition comprising a plurality of colloids having the
structure Y--O.sub.u-M.sub.t and a cation counterion, the
composition being suspended in a physiologically compatible buffer,
wherein: Y is a polymer having a molecular weight greater than
about 1000; O is oxygen and u is a number between zero and about
200; and each M is an atom selected from the group of stable
isotopes capable of capturing a neutron, thereby becoming unstable
and emitting a photon having a characteristic energy spectrum, the
photon being selected from the group consisting of a gamma photon,
an x-ray photon or a prompt photon, t being an integer from 1 to
about 10.
40. A composition according to claim 39, wherein each colloid among
the plurality has a distinct molecular weight and is uniquely
associated with a distinct M.
41. A method for quantifying by neutron activation an amount of at
least one compound .OMEGA..sub.i-X.sub.j-M.sub.k, wherein each
.OMEGA..sub.i is a unique organic compound having a molecular
weight greater than about 50; each X.sub.j is at least one chelator
covalently bound to .OMEGA..sub.i; and each M.sub.k is an atom of a
stable isotope of an element and is distinct in identity and has a
nucleus capable of capturing neutrons and thereby emitting photons,
and i, j, and k are each numbers from 1 to 8, i being at least as
great as k, the method comprising: exposing a first container
having .OMEGA..sub.i-X.sub.j-M.sub.k and a second container having
a standard known quantity of M.sub.k to a neutron source using the
same neutron field, such that .OMEGA..sub.i-X.sub.j-M.sub.k and the
M.sub.k standard capture neutrons and emit photons, wherein each
M.sub.k is selected from the group consisting of .sup.45Sc,
.sup.50Cr, .sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu, .sup.103Rh,
.sup.113Cd, .sup.114Cd, .sup.113In, .sup.115In, .sup.123Te,
.sup.133Cs, .sup.139La, .sup.141Pr, .sup.141Nd, .sup.149Sm,
.sup.152Sm, .sup.153Eu, .sup.153Eu, .sup.152Gd, .sup.155Gd,
.sup.157Gd, .sup.159Tb, .sup.158Dy, .sup.160Dy, .sup.161Dy,
.sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.168Yb, .sup.169Tm,
.sup.174Hf, .sup.178Hf, .sup.175Yb, .sup.165Ho, .sup.175Lu,
.sup.176Lu, .sup.181Ta, .sup.185Re, .sup.187Re, .sup.190Ir,
.sup.193Ir, .sup.196Hg, .sup.202Hg, and .sup.197Au; detecting
resulting photon emissions; and comparing photon emissions of
.OMEGA..sub.i-X.sub.j-M.sub.k with photon emissions of the
standard, thereby quantifying the amount of at least one compound
.OMEGA..sub.i-X.sub.j-M.sub.k.
42. A method of evaluating the rate of at least one physiological
process in a subject, the method comprising: administering at least
one test composition to a subject, wherein each test composition is
differently labeled with one of the group of stable isotopes of one
or more elements; obtaining a plurality of samples of a bodily
fluid from the subject, the samples being obtained at different
times after administering the composition; determining by neutron
activation the amount of the at least one test composition in a
volume of the samples; and calculating the rate of change of
concentration over time of the composition in the bodily fluid,
thereby evaluating the rate of the physiological process in the
subject.
43. A method according to claim 42, wherein the rate of the
physiological process is the glomerular filtration rate.
44. A method according to claim 42, wherein the physiological
process is the glomerular integrity rate.
45. A method according to claim 42, wherein the rate of the at
least one physiological process is a glomerular filtration rate and
a glomerular integrity rate.
46. A method according to claim 42, wherein the rate of change of
concentration of the at least one test composition is glomerular
selectivity according to size of the test composition.
47. A method according to claim 42, wherein the rate of change of
concentration of the at least one test composition is glomerular
selectivity according to charge of the test composition.
48. A method according to claim 42, wherein the physiological
process is at least one hepatic function.
49. A method according to claim 42, wherein the physiological
process is at least one gastrointestinal function.
50. A method according to claim 42, wherein evaluating the rate of
the physiological process is evaluating absorption of a bile acid
compound.
51. A method according to claim 42, wherein evaluating the rate of
the physiological process is evaluating cirrhosis.
52. A method according to claim 42, wherein evaluating the rate of
change of the physiological process is evaluating liver function
after liver transplantation.
53. A kit for measuring glomerular integrity rate, comprising: a
test composition X-M and a counterion in a physiologically
compatible solution wherein X is a chelator noncovalently bound to
M, and M is an atom of a stable isotope of an element having a
nucleus capable of capturing a neutron and subsequently emitting a
photon; at least one sample container to collect at least one
samples of a bodily fluid; instructions for use; and a data
recording system.
54. A composition for lot labeling a plurality of sample
containers, the composition comprising at least one stable isotope
of an element and a binding agent, wherein the binding agent
maintains the stable isotope in the container, the stable isotope
having a nucleus capable of capturing a neutron and subsequently
emitting a photon.
55. A composition according to claim 54, wherein the binding agent
is selected from the group consisting of: a polyurethane, a wax, an
oil based adhesive, an organic solvent, a water based adhesive, an
aqueous solvent, an acrylic and a plastic.
56. A method for monitoring neutron flux variation within a set of
samples, the method comprising: providing a lot having a plurality
of sample containers, each container having a predetermined amount
of a first stable isotope; adding a test sample containing a second
stable isotope to each of the containers, wherein the first and
second stable isotopes are different and are selected from the
group consisting Of .sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.103Rh, .sup.113Cd, .sup.114Cd,
.sup.113In, .sup.115In, .sup.123Te, .sup.133Cs, .sup.139La,
.sup.141Pr, .sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151Eu,
.sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159In,
.sup.158Dy, .sup.160Dy, .sup.16Dy, .sup.162Dy, .sup.163Dy,
.sup.164Dy, .sup.168Yb, .sup.169Tm, .sup.174Hf .sup.178Hf,
.sup.175Yb, .sup.165Ho, .sup.175Lu, .sup.176Lu, .sup.181Ta,
.sup.185Re, .sup.187Re, .sup.190Ir, .sup.193Ir, .sup.196Hg,
.sup.202Hg, and .sup.197Au; exposing the containers to a neutron
source; and comparing the resulting photon emissions from each of
the first and second stable isotopes in each container of the lot
to monitor neutron flux variation within the set of samples.
57. A method for associating each of a plurality of tubes with a
particular lot, the method comprising: providing a plurality of
containers having a predetermined amount of a first stable isotope
composition, M, for identification of the lot, and a known amount
of a second stable isotope composition, N, to monitor neutron flux
variations, wherein M and N are different and are selected from the
group consisting of .sup.36S; .sup.45Sc, .sup.50Cr, .sup.51V,
.sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu, .sup.75As, .sup.79Br,
.sup.81Br, .sup.103Rh, .sup.107Ag, .sup.109Ag, .sup.113Cd,
.sup.114Cd, .sup.113 In, .sup.115In, .sup.123Te, .sup.121Sb,
.sup.123Sb, .sup.123Te, .sup.127I, .sup.133Cs, .sup.139La,
.sup.141Pr, .sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151Eu,
.sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb,
.sup.158Dy, .sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy,
.sup.164Dy, .sup.165Ho, .sup.168Yb, .sup.169Tm, .sup.174Hf,
.sup.178Hf, .sup.175Yb, .sup.175Lu, .sup.176Lu, .sup.181 Ta,
.sup.184Os, .sup.185Re, .sup.186W, .sup.187Re, .sup.190Ir,
.sup.190Pt, .sup.193Ir, .sup.196Hg, .sup.206Hg, and .sup.197Au, the
containers configured to receive a test sample, wherein the test
sample is substantially free of M and N; exposing the containers to
a neutron source; and detecting the resulting photon emissions at
spectra characteristic of M and N, so as to associate each tube of
the plurality of tubes with the predetermined quantity of the first
stable isotope, for identification of the lot.
Description
RELATED APPLICATION
[0001] This application claims priority to provisional patent
application U.S. Ser. No. 60/266,647, filed Feb. 5, 2001, the
contents of which are hereby incorporated by reference in entirety
herein.
FIELD OF THE INVENTION
[0002] The invention relates to methods wherein, by recording the
concentration or amount of one or more stable isotopically labeled
xenobiotic compound containing an element detectable after neutron
activation, this xenobiotic compound may be determined in a living
subject in blood, serum, plasma, urine, fecal, biopsy, or other
body fluid or composition.
BACKGROUND OF THE INVENTION
[0003] Neutron activation and stable isotope labeling allows for
the detection of low amounts of molecules in biological systems, as
shown in chromatographs and gel electrophoretograms (1). For many
diagnostic and therapeutic applications, it can be important to
detect small amounts of a molecule of interest in a biological
sample. Present methods for detecting biological compounds or
physiological processes of interest can lack the requisite
sensitivity and non-toxicity for in vivo administration.
SUMMARY OF THE INVENTION
[0004] The invention is based in part on the discovery of highly
sensitive stable isotope-containing compositions that allow for
detection and measurement of small quantities of a biological
molecule in samples taken from a subject. An embodiment of the
invention features a composition comprising a compound having a
structure X-M, wherein X is a chelator, M is an atom of a stable
isotope of an element having a nucleus capable of capturing a
neutron and subsequently emitting a photon, M is noncovalently
bound to X, X being at a concentration at least as great as that of
M, the composition having a counterion and a physiologically
acceptable buffer. In general, the atom of the stable isotope M is
selected from the group consisting of: .sup.45Sc, .sup.50Cr,
.sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu, .sup.103Rh, .sup.113Cd,
.sup.114Cd, .sup.113In, .sup.115In, .sup.123Te, .sup.133Cs,
.sup.139La, .sup.141Pr, .sup.146Nd, .sup.149Sm, .sup.152Sm,
.sup.151Eu, .sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd,
.sup.159Tb, .sup.158Dy, .sup.160Dy, .sup.161Dy, .sup.162Dy,
.sup.163Dy, .sup.164Dy, .sup.168Yb, .sup.169Tm, .sup.174Hf,
.sup.178Hf, .sup.175Yb, .sup.165Ho, .sup.175Lu, .sup.176Lu,
.sup.181Ta, .sup.185Re, .sup.187Re, .sup.190Ir, .sup.193Ir,
.sup.196Hg, .sup.202Hg, and .sup.197Au. The counterion is, for
example, meglumine (1-deoxy-1-methylamino-D-glucitol antimoniate).
The chelator X can be selected from the group consisting of:
diethylenetriaminepentaacetic acid (DTPA),
diethylenetriamine-pentamethylenephosphonic acid (DTPMP),
tetraazacyclododecanetetraacetic acid (DOTA) or a derivative of
DOTA, ethylene-diaminetetraacetic acid (EDTA),
tetraazacyclododecanetetrakis (methylene phosphonic acid) (DOTP),
hydroxypropyl tetraazacylododecanetriacetic acid (HP-DO3A),
diethylenetriaminetriacetic acid bismethylamide (DTPA-BMA), and
MS-325. The concentration of X is between about 100 micromolar and
about 1.5 molar.
[0005] In another embodiment, the invention features a method of
preparing a pharmaceutical composition of a compound having a
structure X-M, the method comprising: providing a solution having X
and M, wherein X is a chelator, and M is an atom of a stable
isotope of an element noncovalently bound to X and having a nucleus
capable of capturing a neutron and subsequently emitting a photon,
and the concentration of X is at least as great as that of M, the
solution being aqueous and having a physiologically acceptable
buffer; and sterilizing the solution. In a related embodiment of
the method, M is selected from the group consisting of: .sup.45Sc,
.sup.50Cr, .sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu, .sup.103Rh,
.sup.113Cd, .sup.114Cd, .sup.113In, .sup.115In, .sup.123Te,
.sup.133CS, .sup.139La, .sup.141Pr, .sup.141Nd, .sup.149Sm,
.sup.152Sm, .sup.151Eu, .sup.153Eu, .sup.152Gd, .sup.155Gd,
.sup.157Gd, .sup.159Tb, .sup.158Dy, .sup.160Dy, .sup.161Dy,
.sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.168Yb, .sup.169Tm,
.sup.174Hf, .sup.178Hf, .sup.175Yb, .sup.165Ho, .sup.175Lu,
.sup.176Lu, .sup.181Ta, .sup.185Re, .sup.187Re, .sup.190Ir,
.sup.193Ir, .sup.196Hg, .sup.202Hg, and .sup.197Au.
[0006] In yet another embodiment, the invention provides a method
for quantifying by neutron activation an amount of a complex having
a structure X-M, the method comprising: exposing each of the X-M
complex and a standard to a neutron source, wherein X is a chelator
and M is an atom of a stable isotope of an element having a nucleus
capable of capturing a neutron and subsequently emitting a photon,
and wherein the standard has a predetermined quantity of M, X-M and
the standard being exposed to the neutron source at the same time,
such that M emits a photon after capture of a neutron; detecting an
emitted photon from each of X-M and the standard; and comparing an
amount of photonic emissions from each of the X-M and the standard,
thereby quantifying the amount of the complex having the structure
X-M.
[0007] The invention in another embodiment features a method of
determining the glomerular filtration rate (GFR) of a subject,
comprising: administering a known quantity of a test substance to
the subject, the test substance having at least one atom of a
stable isotope of an element with a nucleus capable of capturing of
a neutron and subsequently emitting a photon, the test substance
being filtered by the kidneys and detectable by neutron activation
analysis in a sample of a bodily fluid; obtaining at least one
sample of a bodily fluid from the subject at least one
predetermined time interval following administering the test
substance; determining the amount of test substance in a volume of
the at least one sample of the bodily fluid by neutron flux
activation; and calculating the GFR from the amount of photon
emission by the activated element, thereby determining the GFR of
the subject.
[0008] In a related embodiment of this method, determining the
amount of the test substance further involves comparing photon
emission of the activated element in the sample of the bodily fluid
to photon emission from a standard that includes the same stable
isotope and is exposed to the same neutron flux. Another related
embodiment of this method further comprises, prior to administering
the compound to the subject, obtaining a sample from the subject of
at least one bodily fluid for determining a baseline of
concentration of the element. In other various related embodiments
of the method, the test substance is selected, for example, from
the group consisting of Sm-DTPA, La-DTPA, Lu-DTPA, Sm-DOTA,
La-DOTA, and Lu-DOTA; the test substance is, for example, an
iodinated contrast agent; the agent comprises iohexol or
iothalamate; a dose of the test compound administered to the
subject is about one .mu.mol to about 0.5 mmol per kg body weight
of the subject; the test compound is administered, for example,
intravenously; the time interval can be about 10 to about 60
minutes; calculating the GFR an further involve using a
computerized program; and obtaining a sample from the subject
further comprises catheterizing the urethra of the subject.
[0009] The invention features in yet another embodiment a kit for
measuring glomerular filtration rate in a subject, comprising: at
least one vial of a test composition, the test composition having:
a compound of structure X-M, wherein X is a chelator and M is an
atom of a stable isotope of an element having a nucleus capable of
capturing a neutron and subsequently emitting a photon, M being
noncovalently bound to the X, and a counterion, the compound being
dissolved in a physiologically compatible solution; at least one
sample container to collect a bodily fluid; and instructions for
use. The kit in a related embodiment further comprising a data
recording system. The kit can further comprise an internal standard
monitor distributed into each of the sample containers.
[0010] In another embodiment, the invention provides a composition
comprising at least one compound .OMEGA..sub.i-X.sub.j-M.sub.k and
a counterion, wherein: each .OMEGA..sub.i is an organic compound
having a molecular weight greater than about 50; each X.sub.j is at
least one chelator covalently bound to each .OMEGA..sub.i; and each
M.sub.k is noncovalently bound to X and has a nucleus capable of
capturing a neutron and subsequently emitting a photon and is an
atom of a stable isotope of an element selected from the group
consisting of .sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.113Cd, .sup.114Cd, .sup.113In,
.sup.115In, .sup.123Te, .sup.133Cs, .sup.139La, .sup.141Pr,
.sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151Eu, .sup.153Eu,
.sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb, .sup.158Dy,
.sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy, .sup.164Dy,
.sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf, .sup.175Yb,
.sup.165Ho, .sup.175Lu .sup.176Lu, .sup.181 Ta .sup.185Re,
.sup.187Re, .sup.190Ir, .sup.193Ir, .sup.196Hg, .sup.202Hg, and
.sup.197Au, wherein each M.sub.k is distinct in identity; i, j, and
k each being a number from 1 to 8, wherein i is at least equal to
k.
[0011] In another embodiment, the invention provides a composition
comprising at least one compound .OMEGA..sub.i-X.sub.j-M.sub.k, at
least one compound .PSI.-N, and a cationic counterion, wherein:
each .OMEGA. is an organic compound having a molecular weight
greater than about 50; each X is at least one chelator covalently
bound to .OMEGA. and noncovalently bound to M; T is a chelator
noncovalently bound to N; N is different from M, N and M each being
an atom of a stable isotope of an element selected from the group
consisting of .sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.103Rh, .sup.113Cd, .sup.114Cd, 1131n,
.sup.115In, .sup.123Te, .sup.133Cs, .sup.139La, .sup.141Pr,
.sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151Eu, .sup.153Eu,
.sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb, .sup.158Dy,
.sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy, .sup.164Dy,
.sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf, .sup.175Yb,
.sup.165Ho, .sup.175Lu, .sup.176Lu, .sup.181Ta, .sup.185Re,
.sup.187Re, .sup.190Ir, .sup.193Ir, .sup.196Hg, .sup.202Hg, and
.sup.197Au, each M and N, independently, having a nucleus capable
of capturing a neutron and subsequently emitting a photon; and i, j
and k are independently each a number from 1 to about 8.
[0012] In another embodiment, the invention provides a composition
comprising: a compound .OMEGA..sub.i-M and a cationic counterion,
wherein: each .OMEGA. is an organic compound having a molecular
weight greater than about 50, i being a number from 1 to about 8;
and M is an atom of a stable isotope of an element selected from
the group of elements consisting of .sup.36S, .sup.74Se, .sup.79Br,
.sup.81Br, .sup.107Ag, .sup.109Ag, .sup.127I, .sup.197Au,
.sup.190Pt, and .sup.196Hg, wherein M is covalently bound to
.OMEGA. and has a nucleus capable of capturing of a neutron and
subsequently emitting a photon. In various related embodiments of
this composition, the at least one .OMEGA..sub.i-X-M.sub.i compound
differs in molecular weight range from the other compounds, the
.OMEGA..sub.i-X-M.sub.i compounds having the same net charge; the
.OMEGA..sub.i-X-M.sub.i compounds have different net charges and
about the same molecular weight; and .OMEGA..sub.i is a
polymer.
[0013] In various additional related embodiments of this
composition, the polymer is selected from the group consisting of a
polysaccharide, a polypeptide, and a polynucleotide; the
polysaccharide is a ficoll, a dextran, a pullulan, a starch, or a
hydroxyethylstarch; the polypeptide is covalently attached to a
polyethylene glycol polymer; and the non-covalently bound chelator
is a bile acid compound. In various additional related embodiments
of this composition, the bile acid compound is selected from the
group consisting of cholic acid, cholic acid taurine,
chenodeoxycholic, deoxycholic acid, homocholic acid taurine, and
lithocholic acid; the bile acid compound is a synthetic derivative
of a bile acid; the non-covalently bound chelator is a drug or a
drug metabolite; .OMEGA..sub.i is selected from the group
consisting of a hormone and a hormone antagonist; .OMEGA..sub.i is
a steroid hormone; and the non-covalently bound chelator is
selected from the group consisting of an antibiotic, a
tranquilizer, a vitamin, a narcotic, a cannabinoid, a barbiturate,
and an alkaloid.
[0014] An embodiment of the invention also provides a composition
comprising a plurality of colloids having the structure
Y--O.sub.u-M.sub.t and a cation counterion, the composition being
suspended in a physiologically compatible buffer, wherein: Y is a
polymer having a molecular weight greater than about 1000; O is
oxygen and u is a number between zero and about 200; and each M is
an atom selected from the group of stable isotopes capable of
capturing a neutron, thereby becoming unstable and emitting a
photon having a characteristic energy spectrum, the photon being
selected from the group consisting of a gamma photon, an x-ray
photon or a prompt photon, t being an integer from 1 to about 10.
In a related embodiment, each colloid among the plurality has a
distinct molecular weight and is uniquely associated with a
distinct M.
[0015] An embodiment of the invention provides a method for
quantifying by neutron activation an amount of at least one
compound .OMEGA..sub.i-X.sub.j-M.sub.k, wherein each .OMEGA..sub.i
is a unique organic compound having a molecular weight greater than
about 50; each X.sub.j is at least one chelator covalently bound to
.OMEGA..sub.i; and each M.sub.k is an atom of a stable isotope of
an element and is distinct in identity and has a nucleus capable of
capturing neutrons and thereby emitting photons, and i, j, and k
are each numbers from 1 to 8, i being at least as great as k, the
method comprising: exposing a first container having
.OMEGA..sub.i-X.sub.j-M.sub.k and a second container having a
standard known quantity of M.sub.k to a neutron source using the
same neutron field, such that .OMEGA..sub.i-X.sub.i-M.sub.k and the
M.sub.k standard capture neutrons and emit photons, wherein each
M.sub.k is selected from the group consisting of .sup.45Sc,
.sup.50Cr, .sup.55Mn, .sup.58Fe, .sup.59Co, .sup.63Cu, .sup.103Rh,
.sup.113Cd, .sup.114Cd, .sup.113In, .sup.115In, .sup.123Te,
.sup.133Cs, .sup.139La, .sup.141Pr, .sup.146Nd, .sup.149Sm,
.sup.152Sm, .sup.151Eu, .sup.153Eu, .sup.152Gd, .sup.155Gd,
.sup.157Gd, .sup.159 Tb, .sup.158Dy, .sup.160Dy, .sup.161Dy,
.sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.168Yb, .sup.169Tm,
.sup.174Hf, .sup.178Hf, .sup.175Yb, .sup.165Ho, .sup.175Lu,
.sup.176Lu, .sup.1Ta, .sup.185Re, .sup.187Re, .sup.190Ir,
.sup.193Ir, .sup.196Hg, .sup.202Hg, and .sup.197Au; detecting
resulting photon emissions; and comparing photon emissions of
.OMEGA..sub.i-X.sub.i-M.sub.k with photon emissions of the
standard, thereby quantifying the amount of at least one compound
.OMEGA..sub.i-X.sub.i-M.sub.k.
[0016] An embodiment of the invention provides a method of
evaluating the rate of at least one physiological process in a
subject, the method comprising: administering at least one test
composition to a subject, wherein each test composition is
differently labeled with one of the group of stable isotopes of one
or more elements; obtaining a plurality of samples of a bodily
fluid from the subject, the samples being obtained at different
times after administering the composition; determining by neutron
activation the amount of the at least one test composition in a
volume of the samples; and calculating the rate of change of
concentration over time of the composition in the bodily fluid,
thereby evaluating the rate of the physiological process in the
subject. In a related embodiment of this method, the rate of the
physiological process is the glomerular filtration rate.
[0017] In various additional related embodiments of the method, the
physiological process is the glomerular integrity rate; the rate of
the at least one physiological process is a glomerular filtration
rate and a glomerular integrity rate; the rate of change of
concentration of the at least one test composition is glomerular
selectivity according to size of the test composition; the rate of
change of concentration of the at least one test composition is
glomerular selectivity according to charge of the test composition;
the physiological process is at least one hepatic function; the
physiological process is at least one gastrointestinal function;
and the rate of the physiological process is evaluating absorption
of a bile acid compound.
[0018] In related embodiments of the method, evaluating the rate of
the physiological process is evaluating cirrhosis; further,
evaluating the rate of change of the physiological process is
evaluating liver function after liver transplantation.
[0019] A featured embodiment of the invention provides a kit for
measuring glomerular integrity rate, comprising: a test composition
X-M and a counterion in a physiologically compatible solution
wherein X is a chelator noncovalently bound to M, and M is an atom
of a stable isotope of an element having a nucleus capable of
capturing a neutron and subsequently emitting a photon; at least
one sample container to collect at least one samples of a bodily
fluid; instructions for use; and a data recording system.
[0020] An embodiment of the invention provides a composition for
lot labeling a plurality of sample containers, the composition
comprising at least one stable isotope of an element and a binding
agent, wherein the binding agent maintains the stable isotope in
the container, the stable isotope having a nucleus capable of
capturing a neutron and subsequently emitting a photon.
[0021] Accordingly, the binding agent is selected from the group
consisting of: a polyurethane, a wax, an oil based adhesive, an
organic solvent, a water based adhesive, an aqueous solvent, an
acrylic and a plastic.
[0022] An embodiment of the invention provides a method for
monitoring neutron flux variation within a set of samples, the
method comprising: providing a lot having a plurality of sample
containers, each container having a predetermined amount of a first
stable isotope; adding a test sample containing a second stable
isotope to each of the containers, wherein the first and second
stable isotopes are different and are selected from the group
consisting of .sup.45Sc, .sup.50Cr, .sup.55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.103Rh, .sup.113Cd, .sup.14Cd,
.sup.113In, .sup.115In, .sup.123Te, .sup.133Cs, .sup.139La,
.sup.141Pr .sup.146Nd, .sup.149Sm, .sup.152Sm, .sup.151E
.sup.153Eu, .sup.152Gd, .sup.155Gd, .sup.157Gd, .sup.159Tb,
.sup.158Dy, .sup.160Dy, .sup.161Dy, .sup.162Dy, .sup.163Dy,
.sup.164Dy, .sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf,
.sup.175Yb, .sup.165Ho, .sup.175Lu, .sup.176Lu, .sup.181Ta,
.sup.185Re, .sup.187Re, .sup.190Ir, .sup.193Ir, .sup.196Hg,
.sup.202Hg, and .sup.197Au; exposing the containers to a neutron
source; and comparing the resulting photon emissions from each of
the first and second stable isotopes in each container of the lot
to monitor neutron flux variation within the set of samples.
[0023] An embodiment of the invention provides a method for
associating each of a plurality of tubes with a particular lot, the
method comprising: providing a plurality of containers having a
predetermined amount of a first stable isotope composition, M, for
identification of the lot, and a known amount of a second stable
isotope composition, N, to monitor neutron flux variations, wherein
M and N are different and are selected from the group consisting of
.sup.36S, .sup.45Sc, .sup.50Cr, .sup.51V, .sup.55Mn, .sup.58Fe,
.sup.59Co, .sup.63Cu, .sup.75As, .sup.79Br, .sup.81Br, .sup.103Rh,
.sup.107Ag, .sup.109Ag, .sup.113Cd, .sup.114Cd, .sup.113In,
.sup.115In, .sup.123Te, .sup.121Sb, .sup.123 Sb, .sup.123Te,
.sup.127I, .sup.133Cs, .sup.139La, .sup.141Pr, .sup.146Nd,
.sup.149Sm, .sup.152Sm, .sup.151Eu, .sup.153Eu, .sup.152Gd,
.sup.155Gd, .sup.157Gd, .sup.159Tb, .sup.158Dy, .sup.160Dy,
.sup.161Dy, .sup.162Dy, .sup.163Dy, .sup.164Dy, .sup.165Ho,
.sup.168Yb, .sup.169Tm, .sup.174Hf, .sup.178Hf, .sup.175Yb,
.sup.175Lu, .sup.176Lu, .sup.181Ta, .sup.184Os, .sup.185Re,
.sup.186W, .sup.187Re, .sup.190Ir, .sup.190Pt, .sup.193Ir,
.sup.196Hg, .sup.206Hg, and .sup.197Au, the containers configured
to receive a test sample, wherein the test sample is substantially
free of M and N; exposing the containers to a neutron source; and
detecting the resulting photon emissions at spectra characteristic
of M and N, so as to associate each tube of the plurality of tubes
with the predetermined quantity of the first stable isotope, for
identification of the lot. The phrase, "substantially free" for
example of M and N, shall mean that the sample is at least about
90% free, for example at least about 95% free, for example at least
about 98% free, and for example, at least about 99% free of M and
N, on a solute basis, or on a dry weight basis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic design of the general principle of
neutron activation.
[0025] FIG. 2 is a spectrum of a sample containing 8 isotopes
measured simultaneously using a photonic gamma counter. The x-axis
units are expressed in kilo electron volts representing the energy
of the photons. The y-axis shows the frequency in dpm of photon
emissions. The identification of each peak is given in the table
below. TABLE-US-00001 Energy (kev) Isotope 103.2 .sup.152Sm (n,
.gamma.) .sup.153Sm 112.95 .sup.176Lu (n, .gamma.) .sup.177Lu
208.36 .sup.176Lu (n, .gamma.) .sup.177Lu 295.95 .sup.191Ir (n,
.gamma.) .sup.192Ir 308.46 .sup.191Ir (n, .gamma.) .sup.192Ir
316.50 .sup.191Ir (n, .gamma.) .sup.192Ir 328.5 .sup.193Ir (n,
.gamma.) .sup.193Ir 338.8 .sup.193Ir (n, .gamma.) .sup.193Ir 411.8
.sup.197Au (n, .gamma.) .sup.198Au 554.3 .sup.81Br (n, .gamma.)
.sup.82Br 559.1 .sup.75As (n, .gamma.) .sup.76As 564.1 .sup.121Sb
(n, .gamma.) .sup.122Sb
[0026] FIG. 3 is a graph that illustrates the relationship between
the blood concentration of a test compound, for example, to test
glomular filtration rate over time following bolus injection of the
compound. The blood concentration of the test compound will
increase sharply and then decrease over time until reaching its
preinjection concentration in a normal subject. When organ
impairment, for example, kidney impairment occurs, the blood
concentration of the test compound will decrease more slowly and
take a longer time to reach preinjection levels. In rare cases
organ function may be increased compared to normal function in
which case test substance blood concentration will decline more
rapidly than in a normal subject. The time scale illustrates points
from an 8 hour total time course.
[0027] FIG. 4 is a graph that illustrates the relationship between
the blood concentration of a test compound and time following
injection by constant infusion. Upon initiation of the infusion the
measured blood concentration of the test compound will increase
sharply, and will then become constant for a normal patient at
steady state where the excretion rate equals the rate of infusion.
When organ impairment occurs, the value of a test compound will
continue to increase over time. The time scale illustrates points
from an 8 hour total time course.
[0028] FIG. 5 is a graph that shows the kinetics of removal from
blood of 20 nm diameter gold colloid particles coated with
lactosylated albumin or albumin. Rats were injected with gold
colloid coated with lactosylated albumin in the absence (squares)
or presence of asialofetuin (ovals), or with gold colloid coated
with albumin (triangles). Samples of blood were removed at the
indicated times and the percent of gold remaining in the blood
(normalized for gold concentration at time equal to zero) was
determined using neutron activation analysis. Values presented in
the figure represent the mean value obtained with three rats.
[0029] FIG. 6 is a graph that predicts clearance of plasma samarium
for 60-minutes after injection of Sm-cholic acid. Solid lines
represent samples obtained from patients with cirrhosis, and have a
mean t.sub.1/2 of 120.7.+-.53.9 minutes. Dashed lines represent
subjects having a mean t.sub.1/2 of 30.7.+-.6.2 minutes. Cirrhosis
verses normal group is p=0.006. The bold lines represent the
respective mean values of each of the two groups.
[0030] FIG. 7 is a graph showing daily excretion of Sm-TCA and
Se-CAT tracers of bile acid, expressed as percentage of the
administered doses. The paired values as measured by both tracers
of detection is represented by the equation y=0.97x+0.52, with a
coefficient of correlation of r=0.99.
[0031] FIG. 8 is a graph showing half time of elimination of bile
acid tracers. The paired values (in days) as measured for both
tracers is represented by the equation y=1.01x-0.05, with a
coefficient of correlation of r=1.00.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0032] A method is provided for evaluating the clearance rate of a
xenobiotic compound from a living subject, thereby providing a
noninvasive method for determining the status of the (excretory)
organs of the subject and a method for determining the proper
dosing regimen of a pharmacologically active compound to be
administered to the subject. Also provided are compositions of
xenobiotics containing stable isotopes, both of natural abundance
and enriched, that can be subject to neutron activation and thereby
used to determine their amount and concentration.
[0033] More specifically, an embodiment of this invention relates
to a method of determining the glomerular filtration rate (GFR) and
the glomerular sieving function (GSF) of a subject that comprises
determining the concentration of a stable isotope in serum and
urine samples obtained from a subject given a substance detectable
by neutron activation, e.g., Sm-DTPA. The stable-isotope labeled
substances are filtered by the kidney in accordance with specified
formulas. More particularly, an embodiment of this invention
provides a method that compares the concentration of the stable
isotope before and after its administration to a patient. The
present method is non-radioactive, safe to the patient and the
health practitioner, extremely accurate, and easy to perform.
Stable Isotope Labeling.
[0034] "Stable isotope labeling" means conjugating a suitable
stable isotope with a molecule or chemical entity of interest. See
(I) and U.S. Pat. No. 5,071,775, which is incorporated herein by
reference. Representative stable isotopes are listed in Table 1.
Molecules and chemical entities of interest include but are not
limited to chelates, proteins, nucleic acids, lipids,
polysaccharides, and colloids. Stable isotopes do not emit
radiation and normally can only be measured on a mass basis. Some
stable isotopes, however, can be exposed to neutrons and upon
capture of a neutron by the nucleus of the atom, become thereby
unstable. The newly formed unstable atom will de-excite by emitting
an energetic particle such as an electron or photon. The emitted
photon can then be measured using high-resolution gamma
spectroscopy.
[0035] Elements that are found only in trace amounts in biological
tissues are best suited for stable isotope labeling and neutron
activation. Examples of such trace elements include samarium,
lanthanum, and gold. Samarium and lanthanum may be combined with
biologicals through the use of chelators that are covalently
attached to the biological. Gold serves best as a stable colloid
coated with the biological reagent. Stable isotopes do not emit
radiation but after neutron activation, can be detected in blood
samples and other isolated tissues. The advantage of the use of
stable isotopes for biological measurements is their sensitivity,
absence of radiation, and the ability to measure multiple elements
simultaneously.
[0036] Stable isotopes may be used in their natural abundance, or
as enriched isotopes. Use of enriched isotopes in some instances
allows the use of two or more isotopes of the same element as
labels that can be assayed simultaneously. For instance, two
isotopes of antimony, antimony 121 and antimony-123, provide an
example of an element with two isotopes that can serve as stable
isotope labels.
Quantitation of Stable Isotopes.
[0037] Quantitation of stable isotopes typically, but not always,
includes three steps: activating the stable isotope by exposure to
a neutron field, allowing a time interval of differential isotopic
decay during which certain omnipresent isotopes decay, and
monitoring of emission after a time period to measure photonic
emissions. Activating stable isotopes is accomplished by exposure
to neutrons generated typically by about a 0.1 to a 20 megawatt
nuclear reactor, for example, a 1 to 20 megawatt nuclear reactor,
certain isotopes such as californium, or an electronic source such
as a particle accelerator. Exposure varies from about 5 to about
120 minutes, for example, from about one to about 5 minutes, from
about 5 to about 15 minutes, from about 15 minutes to about 60
minutes, and from about 60 minutes to about 90 minutes. A 15 minute
exposure is usually used as this provides sufficient neutron
exposure while allowing adequate time to manipulate the next round
of samples for exposure. Increased sensitivity of detection of
stable isotope can be gained by increased time of exposure to the
neutron field. A "neutron source" as used herein means any device
that produces a field of neutrons, such as a nuclear reactor having
a range of about 0.1 to 20 megawatts, an isotopic source, and an
electronic source.
[0038] A "differential decay period" allows short-lived omnipresent
isotopes, such as sodium, to decay, leaving longer lived isotopes
of interest in a better medium to be measured with a lower
background. This decay period generally is from about 1 to about 5
days, depending upon the relative amounts of each of the sodium and
the isotopes of interest. During the measurement of prompt photons,
the differential decay period is omitted.
[0039] Depending upon the type of isotope exposed to neutrons,
three types of photonic emissions are produced (Table 1). These are
gamma rays, x-rays, and prompt photons whose emission energy ranges
are about 60-2500 kev, about 0.005-60 kev, and about 100-20000 kev,
respectively. The half-lives for the various isotopes and
associated half-lives are also included in Table 1. All of these
photons can be detected using a germanium crystal photonic detector
that is able to accumulate photonic emission events across a wide
energy range. An example of the level of resolution obtainable with
such a detector is presented in FIG. 2. Improved resolution and
sensitivity of detection can be obtained by using a Compton
suppressed germanium detector. Accumulation of photonic emissions
is usually referred to as "counting", and the period of counting is
typically about 1 to about 10 minutes. Longer counting times can be
used to increase the sensitivity of detection.
[0040] Detection of photo emissions is achieved using a solid state
crystal such as a germanium crystal, or using a scintillation
detector such as a sodium iodine crystal. Further, photon detection
is accomplished using Compton suppression alone, or Compton
suppression operation in coincidence mode.
[0041] The amount or concentration of isotopes of interest can be
determined using a standard curve, which is generated using a
separate set of tubes containing known amounts of the isotopes of
interest, which are exposed to the same neutron field and treated
in the same way as the samples of interest. TABLE-US-00002 TABLE 1
List of stable for isotopes useful for neutron activation and a
biological applications*. Cross-Section (barns) Detection Element
Isotope Abundance Thermal Fast Half-live (day) Mode Antimony Sb-121
57.30 5.9 200 2.72 INAA Sb-123 42.7 4.0 130 60.2 INAA Lanthanum
La-139 99.1 9.0 12.0 1.68 INAA Samarium Sm-149 13.8 40000 3100 PNAA
Sm-152 26.7 208 3000 1.929 INAA Europium Eu-151 47.8 924 5800
4942.1 INAA Eu-153 53.2 350 1500 3136.45 INAA Gadolinium Gd-157
15.65 255000 800 PNAA Tellurium Te-122 2.6 2.4 80 119.7 INAA
Dysprosium Dy-161 18.9 580 1100 PNAA Dy-162 25.5 1800 2800 PNAA
Dy-163 24.9 130 1600 PNAA Dy-164 28.2 1700 1000 0.1 INAA Lutetium
Lu-176 2.59 2300 1200 6.68 INAA Holmium Ho-165 100 61 680 1.117
INAA Rhenium Re-185 37.4 112 1700 3.777 INAA Hafnium Hf-174 0.16
530 410 70 INAA Hf-178 27.3 50 300 25.1 INAA Hf-180 35.1 13 35 42.4
INAA Iridium Ir-191 37.3 920.14 0 73.83 INAA Ir-193 62.7 112 1400
170 INAA Iodine I-127 100 6.2 150 25 INAA Gold Au-197 100 98.7 1550
2.7 INAA Ytterbium Yb-168 0.13 2300 21000 32.03 INAA Yb-174 31.8
120 60 4.19 INAA *4.sup.th Edition Chart of the Nuclides a General
Electric Company Publication. INAA = Instrumental neutron
activation analysis; PNAA = Prompt neutron activation analysis.
Neutron Activation Technology and its Application to Medicine.
[0042] Neutron activation analysis can provide the research and
clinical communities with capabilities not readily available with
other assay technologies. Neutron activation is well known for its
excellent sensitivity and elemental specificity for the
simultaneous measurement of trace elements. (2) This offers the
potential of being able to measure multiple isotopic tracers per
assay. Neutron activation analysis provides the research and
clinical communities with capabilities not readily available with
other assay technologies.
[0043] Unlike techniques such as MR imaging or NMR spectroscopy
that can only measure (the effect of) one contrast agent at a time,
stable isotope labeling and neutron activation analysis can measure
multiple labels simultaneously. Unlike optical lasers, neutrons can
penetrate solid tissue and opaque-liquid samples, thereby providing
an assay that is completely self-contained and requires minimal
sample preparation. Unlike other element detection methods, such as
atomic absorption spectrophotometry, neutron activation is not
chemically or physically destructive. Therefore, samples can be
archived, re-assayed, and/or undergo additional chemical analysis
following neutron activation. Unlike most optical tracers, many
stable biologically-rare isotopes are nontoxic and can be safely
used in human subjects, including pregnant women and pediatric
subjects.
[0044] Typically only the ex vivo samples of interest are
activated; thus neutron activation can significantly reduce
occupational and patient exposure to radiation and reduce the
amount of low-level radioactive waste generated, e.g. gloves,
protective clothing, animal carcasses, etc. Stable isotopes do not
undergo radioactive decay or cause radiokinetics. Stable isotope
labeled research and clinical products will have a significantly
longer shelf-life compared to many other competing labeling
methods.
[0045] Neutron activation has been used in conjunction with
enriched or biologically-rare isotopes, as substitutes for
radioactive isotopes in laboratory experiments (1, 3) and in
clinical applications. (4, 5) Kitchin et al. (3), for example,
successfully used neutron activation to measure iodine and bromine
for the assay of 5-iodo-2'-deoxyuridine and 5-bromo-2'-deoxyuridine
as DNA precursors for determination of cell mitosis and death
rates. Compared to each of immunocytochemistry and
fluorescent-activated cell sorting, neutron activation-based
studies of DNA synthesis were able to evaluate more cells per assay
(up to 105 more) due to the elimination of signal quenching errors
associated with both beta-radiation and fluorescent counting, and
the method required less labor and in-house laboratory equipment.
In addition, this technique offered improved accuracy and
precision, with coefficients of variation as low as about 3 to
about 5% compared to both immunocytochemistry and flow-activated
cell sorting. Recently, Chou et al. (4) refined a neutron
activation technique for the clinical assay of protein-bound iodine
in blood serum samples. The measurement of protein-bound iodine, as
well as the assay of T4 and T3, is a conventional clinical test of
thyroid function. This refined neutron activation technique
provided a simple and highly sensitive assay (down to a few ppb),
while avoiding systematic and temperature-dependent errors
associated with traditional clinical analytical techniques.
General Principles Underlying Neutron Activation.
[0046] The general principle underlying neutron activation is that
an incident neutron is captured by an atom (the parent nuclide)
forming a radioactive nucleus (the daughter nuclide). As shown in
FIG. 1, two modes of detection are often possible following neutron
capture. The first is the measurement of the prompt gamma ray. This
method is called Prompt Neutron Activation Analysis (PNAA). The
half-life of this emission is usually under one second (see Table 1
for a few examples). The second method, and often more desirable
for many of our applications, is to measure the decay of the
resulting, radioactive daughter nuclide. This method is called
Instrumental Neutron Activation Analysis (INAA).
[0047] With INAA detection, an ideal radioactive nucleus for use as
a label is short-lived and emits a gamma ray during the decay
process (6). The energy of the gamma ray is discrete and distinct
for each stable atom. Specialized, high-resolution detection
equipment can then be used to identify and measure the emitted
gamma ray. The number of emitted gamma rays is directly
proportional to the total mass of the parent isotope, and therefore
is proportional to the total concentration of the labeled research
product contained in the sample. In practice, a sample is exposed
to a flux of neutrons, .phi., for a given time, t. The specific
activity, S, induced in any parent nuclide can be calculated from
the formula: S=6.02.times.10.sup.23.phi..sigma.f
A.sup.-1{0.5}.sup.t.sub./.sup./t.sub.1/2{1-(0.5).sup.t/t.sub.1/2}
where: S is specific activity in disintegrations per unit mass
(s.sup.-1kg.sup.-1), .phi. is flux of neutrons in m.sup.-2s.sup.-1,
.sigma. is cross-section for neutron interaction with parent
nuclide (m.sup.2), f is fractional abundance of the parent nuclide,
A is atomic weight of the parent element, t.sub.1 is time between
activation and counting (hours), t is activation period (hours),
and t.sub.1/2 is half-life of daughter nuclide (in hours).
[0048] The sensitivity of any nuclear reaction can be estimated
using Equation 1. For samarium, the potential reaction is
.sup.152Sm(n, .gamma.).sup.153Sm; t.sup.1/2 is 1.93 d. Therefore,
using a flux of 2.0.times.10.sup.17 m.sup.-2 s.sup.-1 and an
irradiation time of 30-minutes followed by a decay period of
2-days, a specific activity of 1.5.times.10.sup.13 disintegrations
s.sup.-1 kg.sup.-1 is obtained for .sup.153Sm. Conservatively, this
technique can determine less than 10.sup.-14 kg (0.01 ng) of
samarium. Therefore, this assay may theoretically measure less than
65 fmol of labeled marker assuming "only one" samarium atom per
marker molecule.
[0049] Moreover, given recent improvements in detector technology
and computer electronics, such as Compton-suppression equipment,
this sensitivity estimate can be improved by a log. It is important
to recognize that increasing the neutron flux and/or increasing the
duration of the neutron exposure will also improve the sensitivity
of this assay. In addition, using an enriched isotope as the tracer
will also increase sensitivity. For example, recalculating the
specific activity for "enriched" samarium increases the estimated
specific activity to 1.1.times.10.sup.14 disintegrations s.sup.-1
kg.sup.-1 which translates to 16 fmol of labeled marker (f is 1
rather than f is 0.26). Similar results are obtained for lanthanum
having an estimated specific activity of 3.9.times.10.sup.12
disintegrations s.sup.-1 kg.sup.-1. Equation 1 also demonstrates
that this assay only activates a minute population of the stable
element present. Therefore, the assay can be repeated to enhance
sensitivity and/or to retrieve results from expensive experiments
that might otherwise be lost with competing technologies that
requires sample destruction to perform the assay.
[0050] The activation process will also activate other isotopes
present in the sample, adding background noise to the signal,
thereby potentially decreasing the sensitivity of the assay. Given
their relative high concentration in biological samples, sodium and
chloride pose the greatest concern. However, given their short
activated half-lives (t.sub.1/2 of .sup.24Na is 15 h, t.sub.1/2 of
.sup.38Cl is 37 min) compared to the proposed label of interest,
this background activity becomes low following a 2 day decay
period. A period of time to allow a short-lived background isotope
to become low is referred to as a period of differential decay.
Moreover, following a five week decay period, most biological
samples (plus our proposed isotopic-labeled probes) will be covered
under the NRC regulations for exempt concentrations (10 CFR 32.11),
and therefore can be returned to the researcher including non-NRC
licensed laboratories. Because components of embodiments of the
assays herein are not chemically or physically destructive,
researchers can perform additional analyses on the sample. However,
certain highly sensitive radioassay methods, such as
autoradiography techniques, may require a longer decay period to
allow minute amounts of ultra-trace activity still remaining in the
sample to fully decay. It is also important to note that desalting
methods can be adapted to methods herein to help remove NaCl and
other contaminants from samples.
Multiple Counting of Isotopes.
[0051] One of the advantages of stable isotope labeling combined
with neutron activation is the ability to measure multiple isotopes
simultaneously in a single sample. In FIG. 2, we show the spectrum
of a sample containing nine isotopes measured simultaneously using
a high resolution germanium based gamma ray counting system. This
capability permits conducting multiple experiments in a single
animal, or doing multiple medical diagnostics simultaneously in a
patient.
Addition of a Monitor Isotope to Sample Vials to Correct for
Neutron Flux.
[0052] If a standard containing a known mass, m.sub.0, of the
element-of-interest is exposed to the same flux of neutrons, then
determination of the unknown mass, m, within the sample is given by
m=(m.sub.0R/R.sub.0), where R and R.sub.0 are the count rates of
the resultant radioactive nucleus from the sample and standard,
respectively. However, it is difficult to achieve a uniform neutron
flux rate. Therefore, in order to provide an internal standard, a
monitor is used to gauge and correct for neutron flux
non-uniformity. A monitor is an element which is useful because
this element is not expected to be found within the actual sample.
A known concentration of this monitor is placed into both the
standard and samples prior to neutron irradiation. The flux rate
can be "monitored" by measuring and then correcting differences to
the generated specific activity of the monitor. As a result, the
accuracy and precision of measuring the unknown mass is further
enhanced, as follows:
m=R(m.sub.0/R.sub.0)(R.sub.0,m/m.sub.0,m)(m.sub.m/R.sub.m), where
R.sub.m and R.sub.0,m are the count rates of the monitor in the
sample and standard, respectively, and m.sub.m and m.sub.0,m are
their respective masses.
[0053] A monitor is commonly added to samples to account for the
non-uniformity of the neutron flux during neutron activation
analysis.(6) For example, Neer et al. (7) describe the addition of
monitor to samples of interest, however, after the addition of the
samples (post-addition of monitor). Further, no efforts were made
to control the geometric position of the monitor within the sample
tube, i.e. at the bottom, along the side or near the top of the
tube.
[0054] In commercial uses of neutron activation, tubes containing
samples for analysis are received from clients. If tubes are filled
to capacity, addition of monitor can be hindered. In other events,
there is sufficient room to add monitor, but the monitor remains
only at the top of the tube, while with other tubes the monitor may
be able to settle to the bottom. Thus the tubes are corrected for
neutron flux using different geometries in the counting of the
monitor. Variations of several centimeters between the monitor
location and the detector face may occur due to these geometrical
anomalies, resulting in substantial differences in the attending
correction factor. Further, the samples must be opened to add
monitor. In the commercial setting, the provider is often "blind"
to the customer's research. As a result, the provider risks
potential exposure to pathogens within the samples.
[0055] The pre-addition of monitor to the sample tube prior to
shipping of the tube to the customer eliminates all of these
disadvantages. First, the position of the monitor within the tube
is standardized eliminating geometrical variation. Second, sample
vials can remain sealed, eliminating potential exposure to
infectious diseases and toxicants.
[0056] Pre-addition of monitor can be accomplished by various
means. Since monitor isotopes come in a variety of chemical forms,
e.g. water and oil soluble monitor can be added to sample
containers in a variety of binders. Monitor can be added to sample
tubes as a solution dissolved in binders such as oil or water
soluble polyurethanes, waxes, gums, glues and plastics. A variety
of techniques can be used to assure that the monitor is maintained
in the container, i.e., is not lost as a result of further physical
manipulations. The physical location of the monitor is designed to
maintain the monitor, for example, inside the main body of the
container, on the outer surface of the main body of the container,
or in the cap of the container. Further, the monitor can be
maintained in the container because it has been formulated as a
component of the plastic used to mold the container, and further is
evenly distributed throughout the container.
Chemical Bar Coding of Sample Vials.
[0057] The pre-addition of monitor offers the opportunity to add
other stable isotopes along with the monitor, thereby offering the
opportunity to label the tubes chemically, i.e. to chemically bar
code sample tubes. Tubes labeled in this manner allow for the
identification of tube lot when samples are returned. Thus sample
tube tracking is provided, and assures that the customer is using
tubes supplied with a kit of reagents. This control allows for
better reagent performance, and allows the manufactured to
distinguish between its own tubes and other tubes of similar
appearance, thereby allowing improved control of inventory and
billing. Methods of controlling chemical bar coding include
adjusting ratios of the monitor with a second, a third and a fourth
suitable isotope, etc., of a stable element.
Chelates for Complexation of Lanthanides.
[0058] Stable isotope labeling includes the attachment of chelates
to various molecular probes. Probes for measuring hepatic function
are chosen for their ability to cross the hepatocyte membrane, and
eventually be excreted via the bile. Research has focused on the
use of hydrophobic ligands, for example, development of liver
magnetic resonance imaging (MRI) contrast agents has concentrated
on high-spin iron(III) complexes of N,N'-ethylenebis
(2-hydrophenylglycine) (EHPG).(8) Unlike other chelates, EHPG is
hydrophobic due to two phenolic substituents that function as metal
binding groups. Recently, Betebenner et al. (9) examined an
alternate approach of using a hydrophilic chelate, EDTA, which on
its own would not normally cross the hepatocyte membrane. They
demonstrated that .sup.111In-EDTA can be successfully complexed to
cholic acid. Moreover, with in vivo mouse and rabbit models, the
cholic acid-EDTA conjugate and .sup.111In rapidly cleared from
circulation and entered into the liver when injected i.v., and was
subsequently excreted from the liver into the gastrointestinal
tract.
[0059] An extensive study of hydrophilic .sup.153Sm-chelate
complexes was carried out by Goeckeler and others, to develop a
therapeutic agent for treatment of pain associated with metastatic
bone cancer.(10) From a series of 15 chelates, the study identified
a .sup.153Sm-chelate complex, EDTMP
(ethylenediamine-tetramethylenephosphonate; Quadramet, Cytogen,
Princeton, N.J.) which gave high bone uptake and rapid blood
clearance.
Application of Stable Isotope Labeling and Neutron Activation
Analysis to the Measurement of Biological Activities and
Xenobiotics.
Classification of Stable Isotope Labeled Compounds by Molecular
Weight.
[0060] Three classes of stable isotope labeled compounds (for
example, xenobiotics) exemplify this technique for the measurement
of biological functions: (i) low molecular weight compounds, e.g.,
organic compounds (<5000 kDa), represented by rare earth
chelates and chelates of bile acids; (ii) high molecular weight
compounds (>5000 kDa), represented by chelates of polymers, such
as polysaccharides, polypeptides including proteins, and
polynucleotides including nucleic acids; and (iii) colloids.
[0061] Proteins used herein can be pegylated, i.e., chemically
modified by addition of polyethylene glycol (PEG) molecules, to
improve characteristics of the protein such as stability in vivo.
PEG additiona produces proteins that retain non-toxic
characteristics, and confer amphophilic properties, i.e.,
solubility both in water and most organic solvents. Pegylation is
achieved via stable covalent bonds between an amino or sulfhydryl
group of the protein, and a chemically reactive group on the PEG.
The reaction can be controlled by procedures known to one of
ordinary skill in the art of protein chemistry, and yields prtoeins
having a chosen extent of pegylation.
[0062] Examples of these polymer compounds and their use are
presented for measuring renal and hepatic function. The compounds
of these examples are presented for purposes of illustration and
teaching, and should not be construed to represent the limits of
application of such compounds or other compounds of similar nature
and molecular weight. Examples of the application of this
technology for the measurement of other biological functions are
listed in Table 2.
Classification of Stable Isotope Labeled Compounds by Method of
Labeling.
[0063] Compounds of interest may be labeled with stable isotope in
two ways: (i) They may carry the stable isotope as an intrinsic
atom of the molecule of interest. Examples of this method of
labeling include drugs carrying a covalently linked bromine atom as
part of their structure, and iron oxides such as Feridex IV. (ii)
They may be labeled "externally" subsequent to synthesis. Examples
of this second method include labeling DNA, RNA and analogs
(including antisense drugs) with chelates binding appropriate
isotopes of lanthanides (Sm, Lu, La).
Methods of Administration of Stable Isotope Labeled Compounds.
[0064] The stable isotope labeled compound may be administered
orally, parenterally (for example, intravenously,
intraperitoneally, intramuscularly, or subcutaneously), rectally,
or by any other suitable method of introducing such a compound into
a living subject, including inhalation (for example, inhalation of
aerosolized samarium containing compounds, such as by use of a jet
nebulizer).
Definition of Xenobiotic.
[0065] A xenobiotic is a chemical compound or colloid not found
within the body of a test subject under normal physiological
conditions, or found at such low levels that the compound is not
detectable by ordinary methods. As used herein, the term xenobiotic
connotes a compound that is labeled with an atom of a stable
isotope capable of capturing a neutron, the atom thereby becoming
unstable and emitting a photon.
Definition of Physiologiclly Compatible Solutions.
[0066] Stable isotope labeled compounds in general are administered
as physiologically compatible solutions. A physiologically
compatible solution has a pH between about pH 5 to about pH 9, for
example, between about pH 6 to about pH 8. Further, the solution,
when administered in volumes of about 2 ml/kg of the subject's body
weight, should have an osmolarity in the range of about 230 to
about 320 milli-osmolar/kg. This adjustment can be accomplished
using compounds such as sodium chloride, mannitol, or dextrose.
Finally physiologically compatible solutions are sterile. Sterility
can be accomplished using a method such as autoclaving, filtration
using a filter having a pore size of about 0.1 micron, or exposure
to ionizing radiation, such as gamma irradiation.
Definition of Bodily Fluids.
[0067] Bodily fluids include liquids obtained from the body of an
animal or human subject including blood, plasma, serum, saliva,
ascites, cyst fluid, tears, cerebrospinal fluid, digestive juices,
bile, urine, semen, vaginal secretions, milk, and feces.
Determination of the Concentration of a Pharmacologically Active
Compound Used for the Treatment or Prophylaxis of a Disease
Condition.
[0068] An embodiment of the method of the invention is the
determination of the concentration of a pharmacologically active
compound used for the treatment or prophylaxis of a disease
condition in a living subject, and especially to determine the
proper dosing regimen thereof. Although dosing ranges for a species
generally may be known or determined for such compounds, variation
within a species may exist, due, for example, to the sex, age and
state of health of the particular subjects. Thus, in a noninvasive
method for determining the clearance rate based on excretion and/or
metabolism over time for a particular subject, it is advantageous
to avoid over- or under-dosing. In this embodiment, the stable
isotope labeled compound may be any pharmacologically active
compound which is labeled with a stable isotope suitable for
neutron activation and detection, such as the appropriate isotopes
chosen from pharmaceuticals containing elements Sm, La, Gd, Ir, Yb,
Au, Fe, As, Sb, Pt, I, and Br. Among those pharmaceuticals
currently available possessing these elements are Feridex (Fe),
cis-platinum (Pt), Magnavist (Gd), iohexol, and sodium
aurothiomalate (trade name Myocrisin) (Au).
[0069] In this embodiment, a neutron activatible-detectible,
pharmacologically active xenobiotic compound (i.e., a compound not
found endogenously in a normal subject), may be administered to a
subject, and the concentration of that compound followed over time
by the present method. The amount and timing of the dosage to be
administered to a particular subject may then be adjusted, as
appropriate, to maintain desired levels in the subject of the
compound over the course of the treatment.
Determination of the Concentration of a Pharmacologically Inactive
Compound Used for the Diagnosis of a Disease Condition.
[0070] Another embodiment of the invention is determination of the
clearance rate. The clearance rate comprises whether or not
clearance occurs, for example, as measured by a decrease in
relative or absolute terms of the compound as a function of time of
excretion a xenobiotic compound from a living subject. The
clearance rate provides information as to the functional status of
the excretory organs of that subject, such as the kidneys, liver
and lungs.
[0071] In one embodiment, for example, the absence of removal of
the administered compound from the body, or removal at a rate below
that found in healthy subjects, assists in diagnosing dysfunction
of the excretory organ, or in monitoring the progress of disease in
that organ. Stable isotope labeled compounds which may be employed
in this embodiment are those compounds that are cleared by the
organ of interest, are not substantially metabolized by the
subject, and are not cleared concurrently by organs other than the
organ or organs of interest.
[0072] In another embodiment of methods of the invention, the
glomerular filtration function of a living subject is measured, for
example, by determining the half-life time for glomerular
filtration of a stable isotope labeled compound, cleared through
the kidneys, allowing evaluation of the health of these organs. An
optimum stable isotope labeled compound to be employed in this
embodiment is one which is substantially, or even completely
removed from the subject through the kidneys, and which is neither
secreted nor reabsorbed by the renal tubules. Paramagnetic contrast
agents and analogs labeled with stable isotopes are particularly
useful for this purpose, for example those which are chelates of
samarium. Examples of the latter are
.sup.152Sm-diethylenetriaminepentaacetic acid (152 m-DTPA, for
example, .sup.152 m-DTPA disodium or dimeglumine salts),
.sup.52Sm-diethylenetriaminetriacetic acid bismethylamide
(.sup.52Sm-DTPA-BMA), and .sup.152Sm-tetraazacyclododecane
tetraacetic acid (.sup.152Sm-DOTA), for example, gadoteridol,
Sm-hydroxypropyl tetraazacylo dodecanetriacetic acid
(.sup.152SmHP-DO3A). Similar compounds labeled with Gd have been
described, see, for example, in U.S. Pat. No. 4,885,363. The stable
isotope labeled compound may be administered to the subject by any
suitable route, for example, a route that is intravenous,
subcutaneous, intraperitoneal, intramuscular, or oral. Amounts
employed should be suitable for detection, and may, for example, be
about 5 .mu.mol to about 1 mmol, or about 50 .mu.mol to about 0.3
mmol, of agent per kg of body weight of the subject.
Renal Applications
Application of Stable-Isotope Labeling and Neutron Activation to
the Measurement of Glomerular Filtration Rate.
[0073] An application of stable-isotope labeling followed by
neutron activation is measuring kidney function through the
determination of the glomerular filtration rate. Kidney and urinary
tract disease affects more than 20 million Americans, with an
additional 3.3 million having unrecognized and undiagnosed kidney
diseases. Over 250,000 Americans are currently being treated for
end stage renal disease primarily resulting from diabetes,
hypertension and glomerulonephritis. Diagnosis and monitoring of
renal disease is partially based on either a 24 hour creatinine
clearance or on a serum creatinine test. Creatinine clearance test
results have been shown to overestimate actual renal function by up
to 92% in patients with very severe renal disease. Numerous studies
have shown that overestimation of renal function by
creatinine-based tests increases as renal function diminishes.
[0074] A determination of the glomerular filtration rate (GFR) of a
subject and or patient is frequently requested by researchers
and/or physicians to assess renal function. Accurate GFR
determinations are important in the determination of appropriate
dosing of medication, as well as for monitoring of drug induced
nephrotoxicity in a patient.
[0075] The most frequently measured parameters indicative of renal
function are serum creatinine and urea levels. However, much renal
damage must have occured before these values become abnormal, so
that early detection is not possible using these measurements.
Although the creatinine clearance test is simple and does not
require specialized equipment, it is subject to important and well
recognized errors, some of which are described below.
[0076] The accuracy of glomerular filtration rate (GFR)
measurements depends on a "filtration" marker. An ideal filtration
marker would be one that is exclusively filtered by the kidney but
is neither secreted nor reabsorbed by the renal tubules. Creatinine
does not comply with all these requisites. While being filtered by
the patient's kidneys, it is also secreted by it. Thus, glomerular
filtration rates obtained by this method are inaccurate.
[0077] Urine samples for the creatinine clearance test are
typically collected from a subject over a 24 hour period. This long
period of time is burdensome to the patient and to the nursing
staff, and presents repeated opportunities for error. For example,
the patient may forget to save one or more samples, samples may be
spilled, and specimens or collection time points may be
inaccurately recorded by the staff. These limitations of the
creatinine clearance method have led nephrologists to rely on other
techniques.
[0078] An early alternative was utilization of inulin for measuring
glomerular filtration rates (GFR). Inulin is a natural
polysaccharide that is exclusively filtered by the kidney. A
world-wide shortage of inulin, however, combined with the
cumbersome analysis techniques required by the test, have prompted
the use of other methods.
[0079] An alternative test utilizing Technetium-99m-DTPA
(.sup.99mTc-DTPA) as a filtration marker was introduced. Instead of
relying on assay of the presence of chemical as with the creatinine
and inulin tests, the .sup.99mTc-DTPA test relies on measurement of
radioactivity levels in a sample. While the .sup.99mTc-DTPA test
has proven to be accurate, there are various disadvantages to its
implementation. The .sup.99mTc-DTPA test must be performed in an
approved nuclear medicine facility by a registered nuclear
technologist. In addition, the material administered to the patient
is radioactive, and the patient is therefore exposed to a small
dose of radioactivity. These drawbacks have led to a consideration
of other techniques.
[0080] Another radioactive isotope based chelate
(lanthanum-140-DTPA) has also been considered for GFR
measurements.(38,39) A study using .sup.140La-DTPA for the
measurement of GFR in the dog was successful, however due to the
high radiation dose associated with the decay of .sup.140La, its
use is not considered suitable for human application. (38)
[0081] Gadolinium-DTPA (Gd-DTPA) is a paramagnetic substance
(Magnevist, Berlex Laboratories, Cedar Knolls, N.J.) that was
approved in the United States as a magnetic resonance imaging
contrast agent in 1988. Since then it has been used as an enhancer
of magnetic resonance images in tomography studies (U.S. Pat. No.
4,647,447, the entire content of which is incorporated herein by
reference). Gd-DTPA has proven to be an extremely safe and well
tolerated agent, and has been approved for use in children.
[0082] Paramagnetic substances such as Gd-DTPA have been proposed
for the measurement of glomerular filtration rates by NMR
technology (U.S. Pat. No. 5,100,646, the entire content of which is
incorporated herein by reference). This method has failed to find
substantial use, due to the need for expensive and not readily
available equipment for performing NMR measurements. A second
problem with this method is its reliance on elaborate standard
curves that are dependent upon the body fluid used. Third, this
method is dependent upon blood processing to obtain serum. Finally,
this method is limited to the measurement of a single NMR modulator
at a time. Thus measurement of multiple paramagnetic probes can not
be obtained simultaneously, and even further, requires the complete
elimination of the first probe from the subject before the second
probe can be added. A more specific limitation of the technique is
testing in a situation where a probe has been administered
incorrectly. In this case, a new measurement can not be executed
until complete elimination of the paramagnetic probe has occurred,
about 24 hours later, and can thus requires a second office or
clinic visit on a subsequent day by the subject.
[0083] A commercial radioactive technology recently approved for
measurements of GFR (glomerular filtration rate) in a human subject
uses sodium iothalamate .sup.125I as marker. This compound is
radioactive and has all the disadvantages of radioactive materials
listed above. In addition, the half life of .sup.125I is short and
requires monthly shipments of sodium iothalamate 125I to resupply
hospital pharmacies. Unused material is discarded, causing
inefficiencies and increased expense. Finally, the problems
incurred for multiple measurements described above with
paramagnetic probes are also found with radioactive probes.
[0084] Using an exogenous renal clearance marker is the most
accurate method available for assessing kidney function and offers
an attractive alternative or supplement to creatinine assays.
Compounds such as samarium DTPA are ideal for use as GFR probes.
This class of non-radioactive compounds is stable and can be
detected at very low concentrations (10 to 100 times lower than
paramagnetic probes) providing increased measures of safety. The
measurement is made on whole blood. The potential availability of
multiply labeled chelates having identical biological properties
allows the repeat measurement or simultaneous measurement of GFR
and other excretionary systems. Neutron activation is supplied as a
service, eliminating the need for expensive sophisticated equipment
within the clinic, thereby opening GFR assays to the general
physician in tertiary and rural settings. Finally, the use of
stable isotope labeled compounds and neutron activation has not
previously been applied to the measurement of GFR.
Specific Measurement of Glomerular Filtration Rate.
[0085] Measuring glomerular filtration rate is a specific example
of the general method for measuring blood clearance of xenobiotics
labeled with a stable isotope. Glomerular filtration rates can be
measured by the single injection technique (11) or by the
continuous infusion technique.(12) Advantages of the method include
that samarium-DTPA (Gd-DTPA) is filtered exclusively by the kidney,
and is neither secreted nor reabsorbed by the patient's kidneys.
Further, samarium (.sup.149Sm), is not a radioactive element and
therefore does not expose a patient to radioactivity. It is thus an
ideal "filtration marker". Moreover, the stable isotope of
samarium, .sup.152Sm, is excellently suited for neutron activation
due to its neutron cross section, the simplicity of the emission
spectrum of its activated daughter nuclide and the resulting half
life of the daughter nuclide.
[0086] The present methods in certain embodiments thus use direct
measurement of the concentration of a stable isotope, instead of
measurement of radioactivity as is the case with the .sup.99Tc-DTPA
test, and with indirect measurements of concentration such as
relaxivity used with Gd-DTPA for GFR measurements that rely on the
NMR properties of matter.
[0087] The methods of various embodiments of the invention may
suitably be applied to the field of clinical medicine, veterinary
medicine and for research applications. Advantages of various
embodiments of the methods include: [0088] [1] Administering to a
patient a non-radioactive, safe, stable isotope labeled compound,
such as Sm-DTPA. [0089] [2] Performing the method in an outpatient
hospital facility, a doctor's office, or the patient's home. [0090]
[3] Not requiring any special handling or treatment of specimens.
[0091] [4] Not requiring equipment for the clinic, hospital, or
doctor's office, as samples are shipped out for analysis. The
savings on equipment, laboratory space, maintainance and staff
training can reduce hospital expenditures. [0092] [5] Not requiring
labor intensive procedures, but rather performance by a nurse or
other health worker with minimal training. [0093] [6] Availability
of results of the test within two days. [0094] [7] Performing the
method in less time, more accurately, and less inconveniently than
the creatinine clearance test (routine but inaccurate method to
estimate GFR) or the inulin assay of GFR. [0095] [8] Providing a
simple kit that is not radioactive, and is therefore both stable
and safe to handle. Thus the present technology is suitable for
widespread adoption with gains in accuracy and with lower
expenditures.
[0096] In a specific example, this invention provides a method of
determining the glomerular filtration rate (GFR) of a subject, with
the following details: obtaining a serum sample S.sub.pre and a
urine sample U.sub.pre from a subject; administering to the subject
an amount of a stable isotope labeled substance that is filtered by
the kidneys and that is readily detectable by neutron activation in
serum and urine; allowing for the concentration of the substance to
equilibrate between the blood and the extravascular spaces;
allowing the subject to void and discard urine at a time t.sub.A,
wherein A is 0; obtaining a serum sample S.sub.A at a time t.sub.A
wherein A is as described above; making A=A+1, i.e., at the next
time point; allowing the subject to void at a time t.sub.A and
measuring the volume of urine v.sub.A, wherein v.sub.A corresponds
to a time interval (a.sub.A=t.sub.A-t.sub.A-1); separating an
aliquot of the urine sample v.sub.A and obtaining a serum sample
from the subject at the time t.sub.A; calculating a urine rate
(v/a).sub.A from the formula (v/a).sub.A=v.sub.A/a.sub.A; repeating
steps [6] through [9] until the difference among at least three of
the urine rates (v/a) is less than about 2 cc/min, and determining
concentration of the stable isotope label (usually samarium) by
neutron activation of the serum and urine samples corresponding to
the three end time points t.sub.A for the urine rates, wherein i is
0 to p, and p is at least three; obtaining the concentrations of
the stable isotope labeled substance [SI].sub.s.sub.i in the
S.sub.i serum samples and the [SI].sub.U.sub.i in the U.sub.i urine
samples, wherein i is as defined above; and calculating GFR from
the formula GFR = i = 1 p .times. .times. 2 .times. [ SI ] U i + 1
.times. v i + 1 .times. / .times. ( [ SI ] S i + [ SI ] S i + 1 )
.times. / .times. p ##EQU1## wherein p is as described above.
[0097] Other methods of determining glomerular filtration rates
have been reported using for instance Glofil 125 (sodium
iodothalamate-.sup.125I, www.glofil.com), and these methods may
also be applied for this application.
Example of Glomerular Filtration Rate Determination Using the
Single Injection Technique with a Stable Isotope Labeled
Chelate
[0098] The single injection technique for determining the
glomerular filtration rate (GFR) of a subject is performed with the
following details: administering to a subject a specific volume of
an oral water load, e.g., about 20 ml/kg one hour before
administration of the test substance; obtaining a serum sample
S.sub.pre and a urine sample U.sub.pre from the subject;
administering i.v. to the subject a diagnostically effective amount
of a test substance, the test substance being a compound, X-M,
wherein X is a chelator and M is an atom of a stable isotope of an
element, the atom being noncovalently bound to the chelator and
having a nucleus capable of capturing a neutron, thereby becoming a
radioactive isotope of the element that is filtered by the kidneys
and is readily detectable by neutron activation analysis in serum
and urine, and waiting for a specific time interval, which is about
30 to about 60 minutes; collecting a urine sample and a blood
sample, labeled, "Urine discard and Blood #I"; waiting for a
specific time interval, which is about 30 to about 60 minutes, and
collecting a urine and blood sample, labeled, "Urine #1 and Blood
#2"; waiting for a specific time interval, which is about 30 to
about 60 minutes, and collecting a urine and blood sample, labeled,
"Urine #2 and Blood #3"; and determining the concentration of test
substance in blood and urine using neutron activation analysis, and
calculating the clearance rates by using the formula
C=(UV/P).times.(1.73/SA) where C is glomerular filtration rate in
ml/min/l 0.73 m.sup.2, U is urine concentration of test substance
expressed in disintegrations/min/ml, V is urine flow rate in
ml/min, P is mean blood or plasma concentration of test substance
expressed in disintegrations/min/ml, and SA is body surface area in
m.sup.2.
Example of Glomerular Filtration Rate Determination Using the
Continuous Infusion Technique with a Stable Isotope Labeled
Chelate
[0099] The continuous infusion technique for determining the
glomerular filtration rate (GFR) of a subject is performed with in
the following details: administering an oral water load of about
1500 ml two hours before administration of the test substance;
inserting into the bladder a number 14 or 16, for example, French
Foley catheter; infusing lactated Ringer's solution i.v.; dividing
the dose of test substance equally between a priming dose and a
sustaining dose diluted in about 30 to about 60 ml of isotonic
sodium chloride, the test substance being a compound, X-M, wherein
X is a chelator and M is an atom of a stable isotope of an element,
the atom being noncovalently bound to the chelator and having a
nucleus capable of capturing a neutron, thereby becoming a
radioactive isotope of the element that is filtered by the kidneys
and is readily detectable by neutron activation analysis in serum
and urine; injecting the priming dose followed by the sustaining
dose at a rate of for example, 0.5 ml/min and waiting about 40-45
minutes; collecting for example, 5 ml of blood every 15 minutes
three to five times; collecting total urine content associated with
each blood collection and noting the urine volume; and determining
the concentration of test substance in blood and urine using
neutron activation analysis and calculating the clearance rates by
using the formula C is (UV/P), where C is glomerular filtration
rate in ml/min/l 0.73 m.sup.2, U is urine concentration of test
substance expressed in disintegrations/min/ml, V is urine flow rate
in ml/min, and P is mean blood or plasma concentration of test
substance expressed in disintegrations/min/ml.
[0100] The unilateral glomerular filtration rate (GFR) of a subject
may be determined by the use of ureteral catheterization.
[0101] The three methods presented for determining glomerular
filtration rates indicate the importance of hydration of subjects
during the process or immediately proceeding initiation of the
process. Hydration may be accomplished by oral or intravenous
administration of water or an aqueous solution.
[0102] Blood and urine samples are obtained from each
subject/patient. The samples may be stored until the entire
procedure is completed, so that the determinations are all made at
one time. Alternatively, each sample may be subjected to neutron
activation immediately after being drawn. The samples are stored
cold or frozen, for example, at a temperature of about -70.degree.
to about 10.degree. C., for example, at about -30.degree. to about
5.degree. C., in closed containers.
[0103] Suitable stable-isotope labeled substances are
pharmaceutically acceptable compounds or substances that are
filtered by the kidneys, for example, filtered exclusively by the
kidneys, and may be compounds or substances that are neither
secreted nor reabsorbed by the kidneys. Examples are samarium (and
other lanthanide series) analogs of Gd-DO.sub.3A (Bristol-Myers
Squibb, New York, N.Y.), Gd-DTPA-BMA (Nycomed, Amersham, Bucks.,
UK) and Dysoprosium-DTPA (Nycomed, Amersham). Other examples
include the samarium analog of Gd-diethylenetriaminepentaacetic
acid (Gd-DTPA, Berlex, Wayne, N.J.), and the samarium analog of
Gd-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)
(Gd-DOTA, Guerbet, Paris, FR). Other elements that are analogs of
Gd and contain isotopes suitable for neutron activation can be
substituted for Gd in the above listed chelates, including but not
limited to La, Eu, Ir, Yb, and Dy.
[0104] The stable-isotope labeled substance is administered to the
subject by routes known in the art, for example, any of the routes
described herein, for example, i.v. A paramagnetic substance, e.g.,
Sm-DTPA can be administered for example, in an amount of about 0.1
.mu.mol to about 10 .mu.mol per kg body weight. In an embodiment of
the invention, the stable-isotope labeled substance is administered
in an amount of about 2 to about 80 .mu.mol per kg body weight.
However, amounts of Sm-DTPA or other stable-isotope labeled
substances outside of the stated range may also be administered as
long as they are detectable by neutron activation in the blood and
urine samples obtained from the subject. In some cases, the
stable-isotope labeled substance is administered to a subject
subsequent to obtaining the first blood and urine samples, and
which may, in a related embodiment, be used as controls and for the
preparation of standards.
[0105] After a period of time of about 10 to about 120 minutes
after administration of the stable-isotope labeled substance, for
example, a period of about 60 to about 120 minutes, the patient
voids and a first blood sample is obtained, for example, when the
subject is capable of voiding. Alternatively, the subject is
catheterized, and urine samples may be obtained about every 10 to
about every 60 minutes, for example about every 20 to about every
30 minutes.
[0106] In one embodiment, the time interval between subsequently
obtained blood and urine samples is, in general, determined by the
subject. Suitable time intervals are about 10 to about 60 minutes,
for example, about 15 to about 45 minutes. In order to minimize the
number of samples that need to be taken, each subject may be
requested to void every so many minutes, for example, about every
20 minutes.
[0107] Once the volumes and the time interval are obtained for each
sample's time point, they may be recorded into a data recording
system, for example, on a time sheet, or in a notebook having forms
for recordal. Alternatively, the data may be inputted into a data
recording system such as a computer, and the computer may then
calculate a urine rate, or a volume:time interval ratio (v/a).sub.A
from the formula (v/a).sub.A=v.sub.A/a.sub.A wherein v, a and A are
as defined above.
[0108] The patient is then allowed to void again, to obtain another
urine sample, and another blood sample is obtained, and appropriate
steps described above are repeated, until the difference among at
least three of the volume:time ratios is less than about 2 ml/min,
for example, less than about 1 ml/min.
[0109] The number of time intervals for which the collected urine
volume:time interval ratio between sample collections is
substantially equivalent is, however, not fixed at 3 or 4. Any
number of intervals may be encompassed by the present method. In
general, it is observed that having at least three constant
volume:time ratio intervals, will suffice to obtain accurate
results.
[0110] When at least three time intervals are chosen in accordance
with the criterion described above, then the concentrations of the
stable isotope in the urine and corresponding serum samples are
determined. This yields at least nine values, at least five of
which correspond to blood samples and at least four correspond to
urine samples, wherein i is 1 to p, and p is at least 3, but may
also be chosen to be any value greater than 3, such as 4, 6, 10,
and even higher values.
[0111] The concentrations of the stable isotopes are obtained by
weighing each sample, and determining the amount of stable isotope
in the sample by neutron activation.
[0112] The [SI].sub.U.sub.i and [SI].sub.S.sub.i are then utilized
along, with the (v.sub.i.sup.U/a.sub.i) volume:time interval ratios
or urine rates selected to calculate the glomerular filtration rate
(GFR) of the subject in accordance with the mathematical formula of
step [12].
[0113] In one embodiment of the method, the concentrations of the
stable isotope labeled substance in the serum and urine samples are
obtained, then the calculation of the GFR in step [12] may be
conducted in the data recording system that can be provided, for
example, conducted manually, or with a computerized program.
[0114] In addition to the steps described above, the method of the
invention may further comprise, prior to step 1, hydrating a
subject with a hydrating solution. The hydration step is conducted,
for example, via a route that is oral, or is intravenous. However,
other modes of administration are also suitable such as a
combination of oral and parenteral routes of hydration, as is known
in the art.
[0115] Following the injection of the stable-isotope labeled
substance, hydration may be maintained by, e.g., a combination of
oral and intravenous fluids, as determined by the subjects ability
to drink. The fluids may be administered at about 300 to about 500
ml/hr as determined by the subject's condition. Physiologically
acceptable aqueous solutions typically include water for oral
hydration or any other non-caffeinated fluid containing water (e.g.
juices). Suitable intravenous fluids include dextrose, for example,
5% dextrose in water. As is known in the art, intoxication from
administration of pure water or other hypotonic preparations is not
recommended as it can result in patients becoming hyponatremic,
usually a result of renal insufficiency and intravascular
overload.
[0116] The amount of fluid administered by either route should
approximate 5 ml/hr per kg of body weight, to maintain a diuresis
of about 300 to about 400 ml/hr. This rate affects length of the
study, since the frequency of timed intervals may be partially
determined by the rate of urine production. However, in patients
unable to tolerate this amount of fluid, lesser amounts of
hydration are possible.
[0117] Different fluids are appropriate to hydration administered
exclusively via the oral or exclusively via the parenteral route.
Oral administration may consist of water, or non-caffeinated water
based drinks, such as juices, in an initial amount of about 20
ml/kg body weight, with a maintenance amount of about 5 ml/hr per
kg body weight. The exclusively intravenous administration of fluid
comprises, in one embodiment, 5% dextrose in water, at a rate of
about 300 to about 500 ml/hour, depending on patient tolerance.
However, other components can be added to the hydration agent, as
is known in the art.
[0118] In still another embodiment, the above method is conducted
by practicing the hydration step both by the oral and parenteral
routes, for example, oral and intravenous routes. Typically, the
hydration step may be conducted about 10 to about 120 minutes
before step 1, for example, about 30 to about 60 minutes before
that step. However, other time schedules are also suitable.
[0119] In practicing the above method the amount of stable isotope
labeled substance administered the subject should be sufficient for
the detection of stable isotope labeled substance in the urine and
serum samples prepared as described herein. Typically, the amount
of the administered stable isotope labeled substance, e.g., Sm-DTPA
is about 10 to about 100 mmole/kg of body weight of the subject,
for example, about 20 to about 80 mmole per kg of body weight.
However, other amounts of the stable isotope labeled substance may
also be administered as found appropriate.
[0120] An embodiment of invention is a kit intended for practicing
the method of the invention with the hydration step. The hydration
as described above may be conducted via oral or parenteral routes,
or both. A physiologically acceptable, i.e., isotonic sterile
aqueous solution is intended for the parenteral hydration of the
subject.
[0121] Also provided herein is a kit for determining the GFR of a
subject, using a stable isotope labeled substance and neutron
activation analysis, comprising at least one, for example, to about
1000 sample collection vials of uniform weight and sealed
sufficiently tightly to hold steam; at least one, for example, to
about 1000 data collection sheets; and a physiologically-acceptable
sterile aqueous solution of the stable-isotope labeled compound,
comprising a concentration of about 0.001 to about 1.0M of the
compound; for an example, an embodiment of the kit comprises about
10 to about 500 sample collection vials and about 10 to about 500
data collection sheets.
[0122] In yet another embodiment, the sterile stable isotope
labeled solution, e.g., the sterile Sm-DTPA solution, comprises
from about one mmole to about 1.0 mole of the substance, for
example, about one-half M Sm-DTPA. Doses of about one .mu.mol to
about 0.2 mmol/kg weight of the patient are suitably administered.
Lower concentrations are in general used, as long as they provide
an amount sufficient to be detectable in the urine and serum
samples by neutron activation. The accuracy of the results is not
affected by the amount of the substance administered to the
subject, as shown in the examples.
[0123] Generally, a kit may further contain at least one and, for
example, may contain about 1,000 intravenous administration sets,
for example, about 50, or about 500 sets. These sets are sterile,
and are provided in separate enclosed packages, or as preloaded
syringes. Each set is utilized for one patient and then discarded.
The intravenous administration set may comprise a needle, a length
of flexible tubing and a container or reservoir from which the
hydration solution and/or stable isotope labeled compound, e.g.,
the Sm-DTPA solution, are administered.
[0124] In an embodiment of the invention the kit further comprises
a physiologically acceptable sterile aqueous solution comprising
about 5% dextrose by weight.
[0125] The intravenous administration sets described above may also
be utilized. These administration sets may be utilized for the
separate administration of the Sm-DTPA solution and the hydration
of the patient to a subject. Both administration lines may be left
in place until the entire procedure is completed.
Method 2.
[0126] An alternative method for measuring GFR is presented. This
method involves obtaining an initial measurement of a
pre-administration sample having concentration CPRE from a subject,
followed by the administration of an stable isotope labeled neutron
activatable-detectable compound. Subsequent measurements of C, are
then obtained over time, such as about every 5 to about every 90
minutes following administration. The subject may void the compound
via the kidneys during the study time.
[0127] The logarithms of the differences in the concentrations of
C.sub.PRE-C.sub.t before and after administration of the stable
isotope neutron activatable-detectable compound (i.e.,
log(C.sub.PRE-C.sub.t), where C.sub.t represents a concentration in
a sample taken after administration, and C.sub.PRE represents a
concentration taken prior to administration) may be plotted as a
function of time, and the elimination halftime (T.sub.1/2)
calculated from the slope of the log plot according to known
methods.(13) The halftime value(s) so obtained allow a diagnosis to
be made as to the glomerular filtration functioning of the subject,
and hence an evaluation of the health of the kidneys of that
subject. Illustrative of this method but using NMR probes for
detection for calculating glomerular filtration rates are described
in Tweedle.(14)
[0128] Thus, the invention provides a method for the
non-spectroscopic, non-imaging evaluation of the glomerular
filtration functioning of a subject, comprising: [0129] (i)
recording a baseline measurement of the concentration in the
subject's blood of the stable isotope under consideration; [0130]
(ii) administering to the subject an isotope labeled agent, wherein
the agent is capable of renal excretion and is detectable following
neutron activation; [0131] (iii) sampling blood from said subject
at suitable time intervals for determination of stable isotope
concentration; [0132] (iv) calculating the halftime T.sub.1/from
the values of concentration; and [0133] (v) evaluating the
glomerular filtration of said subject from the value T.sub.1/2.
Application of Stable-Isotope Labeling and Neutron Activation to
the Measurement of Glomerular Integrity Rate (GIR), also Known as
Glomerular Size Selectivity (GSS).
[0134] Glomerular integrity rate is a general term for measuring
renal function which can be determined using rate measurements of
change in blood or urine concentration after addition of a test
compound to the blood of a subject. Glomerular integrity rate
measurements include renal blood flow, glomerular size selectivity,
glomerular charge slectivity, and glomerular filtration rate.
[0135] The incidence and prevalence of end-stage renal failure in
the United States continue to increase.(5) In 1995, the incidence
rate was 262 per million population, with a prevalence rate of 975
per million population.(15) The exact number of individuals with
abnormal renal function but not yet at end-stage failure is
difficult to assess. However, crude estimates place this number at
approximately 0.4% of the U.S. population.
[0136] The rate of progression is also difficult to assess. In
general, subjects displaying renal manifestation of certain
systemic diseases, such as diabetes mellitus and systemic lupus
erythematosus, and those with significant proteinuria, seem to have
a more rapid progressive course to end-stage failure. If
intervention is expected to be successful in halting or slowing
such progression, accurate assessment of early manifestations of
renal disease, and renal structure and function, need to be
established.
[0137] Current methods that can best measure these parameters
involve elaborate and expensive laboratory procedures, extensive
hospital stays, radioactive tracers, and/or potentially nephrotoxic
contrast media. As a result, the availability of these assays is
restricted to licensed and/or experienced facilities, limiting or
excluding the ability to effectively monitor patients over the time
course of the disease. These same limitations also restrict
researchers from measuring physiological parameters in experimental
models. Therefore, providers of reliable diagnostics to measure
renal structure and function that are cost-effective, easy-to-use
and can be repeated in subjects to monitor their response to
therapeutic intervention will have a clear advantage in this
market.
[0138] In September 1996, the National Institute of Diabetes and
Digestive and Kidney Diseases of the National Institutes of Health
convened a meeting of experts to review the current status of
diagnosis and treatment of progressive renal disease, and to make
recommendations pertaining to the current status of techniques used
to identify and monitor progression of renal disease.(5) The
conference members concluded that better methods are needed to
identify patients at risk of developing end-stage renal failure and
that more efficient techniques are needed to monitor their response
to therapeutic intervention.
[0139] Currently accepted methods of assessment of renal disease
include measurement of renal function such as serum creatinine and
glomerular filtration rate, (16-18) measurement of proteinuria,
(19) assessment of tubular function, (20) glomerular sieving and
permselectivity, (21, 22) radiologic imaging techniques, (23) and
evaluation of histomorphometry.(24) Given its low-cost and
availability, serum creatinine is the most frequently used test to
assess renal function.
[0140] Unfortunately, by the time the serum creatinine is
"abnormal", the glomerular filtration rate is already substantially
diminished.(25) Other tests that can better assess early-stage
disease involve elaborate and expensive procedures, diminishing
their usefulness as a widespread screening diagnostic and
restricting their repeated use for monitoring the progression of
the disease.
Glomerular Integrity Rate (Glomerular Size-Selectivity).
[0141] The glomerular capillary is a unique and highly efficient
barrier providing a highly permeable structure for the filtration
of water and small molecular substances, while preventing the loss
of important macromolecular substances the size of albumin or
greater. This barrier is the result of glomerular permselective
properties, which are described by two distinct features: [1]
size-selectivity, the ability of the glomerular filter to
progressively hinder the passage of macromolecules from the blood
into Bowman's space, with increasing molecular radius; and [2]
charge-selectivity, the ability of the membrane to restrict
filtration of negatively charged molecules more effectively when
compared to equally sized uncharged or cationic compounds.
[0142] To study normal and diseased glomerulus, researchers have
estimated the fractional clearance of a nonprotein inert polymer,
such as dextran, (23, 26) polyvinylpyrrolidone, (27) and Ficoll
(21), relative to some "freely permeable" reference polymer, such
as inulin. Of these exogenous probes, uncharged dextran, a polymer
of glucopyranose, has been most extensively used to study the
normal barrier function as well as to study the abnormal changes
that occur in the setting of proteinuria. However, dextran's
conformation becomes altered during transglomerular permeation. As
a result, its transport is facilitated, leading to an overestimate
of the effective radii presented by functional glomerular pores to
permeating proteins. In contrast, recent studies have shown that
Ficoll, a polymer of sucrose, more closely approximates that of an
ideal, uncharged globular protein.(26) Like dextran, its component
molecules have a broad distribution of molecular radii, ranging
from those small enough to be freely filtered to those that are
sufficiently large to be impermeant. Ficoll also is uncharged,
permitting exclusive evaluation of the size-selective properties of
glomerular capillary walls. As a result, Ficoll has recently become
the polymer-of-choice for researchers studying glomerular
size-selectivity.
[0143] However, current procedures that use non-reabsorbable
polymers, such as Ficoll, to measure glomerular size-selectivity
are cumbersome in practice. Although optically-labeled polymers are
valuable for studying permeability, (28) sensitivity and toxicity
issues have limited their usefulness, particularly in human
subjects. Therefore, radioactive tags remain the standard reagent.
Polymers are either labeled on site, a labor-intensive procedure
frequently requiring more than 24 hours to complete, or are
purchased pre-labeled from a vendor whose labor costs are reflected
in the purchase price. Following infusion of the labeled polymer,
each collected urine and serum sample is fractionated using various
chromatographic techniques, to separate the polymer into fractions
having narrow size distributions. This separation step employed on
each sample is time consuming, requires specialized equipment and
skilled laboratory labor, and in the clinical arena, exposes
laboratory personnel to agents of infectious diseases.
[0144] Once the size distribution of the inert polymer is known,
one can then characterize the size-selective properties of the
glomerular filtration barrier by calculating the fractional
clearance (or sieving coefficient, .theta.) of the polymer. The
fractional clearance is defined as the clearance of the labeled
polymer divided by the glomerular filtration rate (GFR) of water.
The clearance of inulin is frequently used to measure GFR. (21, 22)
This separate assay adds complexity and increases the cost of
current procedures for measuring glomerular permselectivity. Once
all the data is collected, the fractional clearance is calculated
from the urine concentration (U) and plasma concentration (P) of
the labeled polymer and of inulin as follows: Fractional
clearance=(U/P).sub.polymer/(U/P).sub.insulin
[0145] Given that the labeled polymer is neither reabsorbed nor
secreted, and that the excretion of inulin is also not modified by
tubular function but appears in Bowman's space in the same
concentration as in the plasma water, the ratio of urinary
clearance of the labeled polymer to inulin is equal to the ratio of
the concentration of inulin in Bowman's space to its concentration
in plasma water. Therefore, the fractional clearance value is a
convenient measure of permselectivity, varying from zero, when the
labeled polymer is impeded, to unity when it encounters no
measurable restriction to filtration. For example in normal human
subjects, neutral-labeled molecules with radii less than or equal
to that of inulin (.about.14 .DELTA.) appear in Bowman's space in
the same concentration as in plasma water (i.e, fractional
clearance equals 1).(24) As labeled molecular radius increases,
filtration decreases progressively, reaching low values as the size
of serum albumin (.about.36 .DELTA.) is approached.(24) Therefore,
this measurement can diagnose abnormal renal function and may also
offer the ability to stage the disease and then gauge the effect of
therapeutic intervention.
[0146] This general method for determining glomerular selectivity
has been used to study changes in renal function due to dietary
influences, (29) disease, (21, 22) organ transplantation, (19) and
therapeutic interventions. Despite the technical difficulties, it
is clear that this technique provides unique insights into the
mechanisms of proteinuria in experimental models and in humans and
can play an important role in evaluating the effectiveness of
dietary and pharmacological therapies. A review by the National
Institute of Diabetes and Digestive and Kidney Diseases of the
National Institutes of Health states that issues related to cost,
technical analysis and modeling of data derived from glomerular
selectivity studies using current methodology preclude its
wide-spread use, and that research should be directed to overcoming
these barriers.(15)
[0147] In embodiments of the invention, pre-sized polymers of
distinct molecular weight and narrow non overlapping size
distribution are each labeled with a different stable isotope. When
a set of these molecular markers are administered simultaneously,
their passage across the glomerulus can be determined in a single
measurement and in the absence of any separation steps.
[0148] The adaptation of stable isotope labeling and neutron
activation to the measurement of glomerular size selectivity thus
offers an innovative method to assess this renal parameter.
Advantages include, first, that this approach is non-radioactive,
and eliminates the cumbersome step of post-separating macromolecule
fragments found in each of the urine and serum samples. The
stable-isotope method is less labor intensive and less expensive
than conventional methods. Second, with simplified sample handling
(no chromatography), a safer environment is provided for the
technologist. Third, multiple molecular markers of different sizes
can each be labeled with a different stable isotope probe,
providing a method to quantitate the extent of glomerular
deterioration in a single measurement. Fourth, stable-isotope
probes can also be used to known labeled reference polymers of
proved utility, such as inulin or others, (17) and chelates such as
DTPA and DOTA (described above under GFR). Fifth the combined
administration of multiple molecular markers together with a GFR
marker to the subject will simultaneously obtain a GFR measurement
and glomerular size-selectivity data. Unique diagnostic information
is obtained while consolidating sample collection and data
analysis. Altogether, stable-isotope labeling and neutron
activation applied to glomerular size selectivity determinations
provide an improved way of handling and processing samples that is
less labor intensive, less expensive, and provides more information
in a shorter time, compared to current methodology which relies on
the separate determination of these two parameters.
[0149] In addition to providing unique clinical opportunities, a
nonradioactive and nontoxic method of measuring glomerular
selectivity in research subjects and in humans will accelerate the
development of effective research products that will allow clinical
investigators to better understand the normal and pathophysiologic
basis of macromolecular permeation across the glomerular filtration
barrier.
Hepatic Applications
Application of Stable-Isotope Labeling and Neutron Activation to
the Measurement of Bile Acids.
[0150] In the United States, 62 million people are diagnosed with
digestive disorders each year, resulting in nearly 200 million sick
days, 50 million visits to physicians, 10 million hospitalizations,
and nearly 200,000 deaths per year. Given the insidious onset of
hepatic disease, many patients are misdiagnosed, or go undetected
until they are clinically advanced. Furthermore, most digestive
diseases are complex, having subtle symptoms that further confound
detection and diagnosis. Because of this, patients can expect to
undergo extensive and expensive diagnostic tests before a correct
diagnosis is reached and an effective therapy can begin. For
example in 1992, direct healthcare expenditures approached $107
billion for diagnosing and treating digestive diseases. Therefore,
the development of more reliable diagnostics to measure specific
functional parameters of digestion that are easy-to-use and can be
safely repeated in patients to monitor their response to
therapeutic intervention can reduce both human suffering and
overall healthcare costs. Applications of these improved methods to
screening diagnostics that can accurately detect patients in the
early stages of "specific" hepatic diseases can improve prognosis,
reduce suffering, and serve as a means to identify patients at high
risk. In addition, improved methods to measure functional
parameters will aid research directed toward the development of
more effective therapies.
Bile Acids, Hepatic Circulation, and Clinical Application.
[0151] The bile acid pool consists of primary, secondary and
tertiary bile acids. Primary bile acids, cholic and
chenodeoxycholic acids, are formed in the liver from cholesterol.
Primary bile acids are converted by intestinal bacteria to
secondary bile acids, deoxycholic acid and lithocholic acid. A
fraction of chenodeoxycholic acid is transformed into the tertiary
bile acid ursodeoxycholic acid via 7-ketolithocholic acid. All bile
acids secreted by the liver are conjugated either with glycine or
with taurine. The bile acid pool re-circulates within the
enterohepatic circulation via two physical pumps, the gallbladder
and the small intestine, two chemical pumps, the transport system
of the hepatocyte and the terminal ileal enterocyte, and two
sphincters, the sphincter of Oddi and the ileocecal value. The
physical pumps move bile acids independently of their chemical
structure, whereas the chemical pumps and the absorptive epithelium
discriminates between the different bile acid species. Active
transport by the liver and the ileum is more efficient for a
trihydroxy bile acid, such as cholic acid, than for a dihydroxy
bile acid, such as chenodeoxycholic acid, and is more efficient for
conjugated bile acids than for unconjugated bile acids.
[0152] The bile acid pool is almost completely confined within the
enterohepatic circulation, with less than 1% of the pool present in
the peripheral blood. Serum bile acid levels at any moment are
determined by the instantaneous balance between intestine
absorption and hepatic elimination of bile acids. Input of bile
acids from the intestine into the systemic circulation occurs from
the hepatic circulation or from portal-systemic shunts, a process
which is associated with certain disease states. Therefore,
elevated serum bile acid concentration has been shown to be a
sensitive maker of hepatic dysfunction.(30) An increase of total
serum bile acids usually precedes an elevation of bilirubin in the
early onset of liver damage.(31) Although a rise in total serum
bile acid can indicate the presence of liver disease, it does not
aid in the diagnosis of the type of liver disease.
[0153] Cycling of bile acids in the enterohepatic circulation is
discontinuous and the determination of the pattern of individual
bile acids or the ratio of the primary bile acids (cholic acid to
chenodeoxycholic acid) may indicate the type of liver disease.(30)
The metabolism of i.v. injected .sup.14C-cholic acid in patients
with cirrhosis showed that the removal of circulating cholic acid
in patients with cirrhosis is significantly depressed compared to
healthy subjects. Labeled cholic acid was measured in systemic
plasma in cirrhosis patients for up to 14 days, compared to near
complete clearance of label after only six hours in normal
subjects. Similar findings were also obtained by measuring the
kinetic clearance of orally administrated .sup.14C-cholic acid and
.sup.14C-chenodeoxycholic acid in healthy subjects and in patients
with cirrhosis. In addition, clinical scoring of the severity of
cirrhosis shows that cholic acid synthesis is markedly reduced in
early stages of cirrhosis and decreases continuously with the
advancement of the liver disease.(32) Therefore, an inverse
correlation between synthesis of cholic acid and the severity of
cirrhosis was found. In contrast, chenodeoxycholic acid synthesis
was shown to be relatively unaffected by cirrhosis. These findings
were attributed to a deficiency of one or more enzymes regulating
the formation of precursors of cholic acid in patients with
cirrhosis. Given current limitations placed on the use of
radiolabeled probes, clearance studies of this nature are seldom
used in routine clinical practice.
[0154] Liver dysfunction after liver transplantation is common
during the early post-transplant period. However, it is often
difficult to differentiate primary graft dysfunction, preservation
injury, rejection, infection, and drug toxicity as the cause of
liver cell damage within the graft. It has recently been shown (30)
that biliary bile acids reflect graft dysfunction in pediatric
liver recipients after liver transplantation. In particular, liver
cell damage as a result of preservation injury or rejection lead to
a reduction of biliary cholic acid, resulting in a decrease of
total biliary bile acids and a decrease in the
cholic-to-chenodeoxycholic acid ratio. The
cholic-to-chenodeoxycholic acid ratio may be a useful additional
parameter in detecting allograft rejection. In this study, cholic
acid and chenodeoxycholic acid concentrations in collected bile
samples were measured by reversed phase high pressure liquid
chromatography which involved labor intensive and expensive
laboratory procedures.(30) Therefore, the development of simpler,
easier-to-use, and more cost effective methods of measuring and
tracking bile acid transport and biotransformation can aid liver
transplant research.
[0155] Malabsorption of bile acids is found in a wide variety of
clinical conditions and is therefore an important functional
parameter to monitor. The more commonly found dihydroxy bile salts
have a direct effect on the role of sodium absorption and water
secretion by the colonic mucosa.(33) Thus, an abnormally high
concentration of bile salts in the colon will cause diarrhea, while
abnormally low concentration will result in constipation. The
diarrhea of severe bile acid malabsorption is a debilitating
condition, and patients with even mild cases suffer considerable
discomfort and inconvenience. The prevalence of bile acid
malabsorption exceeds 1 per 100,000 of the adult population.(34)
Despite the fact that effective treatments are available, this
condition is substantially under-diagnosed.
Methods to Measure Bile Acids and Bile Acid Kinetics.
[0156] Uptake, biliary secretion and potential biotransformation of
bile acids are important hepatic functions that play a major role
in the digestion and absorption of triglycerides. However, research
in this area, as well as clinical treatment by implantation, have
been hampered by lack of simple and reliable methods to track bile
acid transport.(35)
[0157] Current methods to measure bile acid concentrations in
collected samples involve cumbersome and expensive laboratory
procedures.(30) A first set of these procedures rely on high
pressure liquid chromatography (HPLC) techniques to isolate and
then measure specific bile acids of interest in collected samples.
Given the complexity of HPLC analysis, this approach is not suited
for routine clinical screening.
[0158] A second approach is to use radioactive labels to evaluate
bile acid transport. Radiolabeled bile acids, such as
[24-.sup.14C]-cholic acid taurine (.sup.14C-CAT),(21,34) and
radiolabeled bile acid derivatives, such as .sup.75Se-homocholic
acid taurine (.sup.75Se-HCAT) which is not currently available in
the United States, (36-38) have simplified laboratory procedures
permitting the detection of bile acid and its derivatives in
biological samples without the need for complex chemical
measurement, purification or both.
[0159] However, one problem with the use of radiaoactive labeled
bile acids is their expense. Not including the costs associated
with the assay and radiation disposal, purchase of a radiolabeled
bile acid, such as .sup.14C-cholic acid, can range from $100-250
per test, and the cost for the bile acid derivative
.sup.75Se-homocholic acid taurine (75Se-HCAT) can exceed $5,000.
Radioactive waste disposal further adds to the cost of using
radioactive tags. Although use of these markers is less
labor-intensive within the hospital setting, requiring less
laboratory preparation before administration and reduced workup
after clinical application, the inconvenience of radioactive agents
includes the need for special licensing, and compliance with
procedures for handling, storage and disposal of contaminated
wastes. Moreover, safety issues further restrict their use in
certain patient subgroups, such as pregnant woman and young
children, and restrict frequency of their use in other subjects to
monitor hepatic dysfunction and therapeutic intervention over the
time course of the disease. Economic issues also restrict the use
of radioactive assays to large facilities able to afford license
fees associated with handling radioactive substances. These same
barriers also restrict researchers from measuring physiological
parameters in experimental models.
[0160] A third approach to measuring bile acids concentrations in
collected samples relies upon optically-labeled bile acid
analogues, such as cholyl-lysyl-fluorescein.(39) Optically-labeled
bile acids are as expensive as .sup.14C-labeled products, however
the cost of processing samples adds significantly to the overall
cost of the assay since these methods are labor intensive requiring
specialized equipment and trained laboratory personnel. In
addition, sensitivity and toxicity issues have limited the in vivo
application of many of these optically-labeled probes, particularly
in humans.
[0161] The development of reliable diagnostics to measure bile acid
malabsorption and to track bile acid transport and
biotransformation in experimental subjects that are cost-effective,
easy-to-use and can be safely repeated in patients and research
subjects to monitor their response to therapeutic intervention is
thus motivated by a set of clear advantages to previous methods.
The invention includes a hepatic assay kit comprising one or more
bile acids that are each separately labeled with a nonradioactive
isotope. Collected samples (tissue biopsies, fecal, and blood
samples) are sent for neutron activation, to measure the
concentration of each stable isotope labeled bile acid, eliminating
the need for the provider to maintain an in-house assay service.
For the researcher/clinician, this approach is nonradioactive, and
the kit is provided in an off-the-shelf ready-to-use form, thereby
freeing the provider from needing special licensing or clinical
pharmacy support. The results of the assay can be obtained within
2448 hours. Any clinic, having trained personnel capable of
collecting serum and/or fecal samples, can provide this assay
service. A hospital setting or specialized department is not
needed. Therefore, the kits and assay service can be offered in
areas of the country and the world that currently are underserved.
In various embodiments, the invention provides a nonradioactive
method to directly measure multiply labeled bile acid
concentrations in biological material, such as serum and fecal
samples, and therefore provides a nontoxic method to measure bile
acid transport in research subjects and in humans. Overall, the
embodiments of the invention are less labor intensive and less
expensive compared to current techniques.
Application of Stable-Isotope Labeling and Neutron Activation to
Measurement of Hepatic Receptor Activity.
[0162] The inability of current diagnostic techniques to predict
liver failure or regeneration has been discussed at length.(40)
Functional evaluation of residual hepatocytes is currently done by
three types of commonly available tests: (i) Quantitation of serum
concentration of substances produced by hepatocytes. (ii)
Quantitation of substances released by damaged hepatocytes. (iii)
Assessment of hepatic metabolic activity.
[0163] Examples of tests in the first category are measurement of
serum albumin and measurement of the prothrombin time. Both of
these tests are limited because they depend not only on hepatic
synthesis of these proteins, but also non-hepatic degradation of
the products.
[0164] In the second category, the most frequently used assays are
those for alanine aminotransferase (ALT) and for aspartate
aminotransferase (AST). These serum enzymes are often used as
indices for liver cell damage. Although these enzymes are clearly
released during hepatocyte damage, the degree of elevation is of
little prognostic value.
[0165] In the third category are a wide variety of tests used to
evaluate hepatic clearance and metabolic function. For example,
.sup.14C-galactose and .sup.14C-aminopyrine have been used to
assess hepatic metabolic reserve. These tests involve measurement
of clearance of an exogenously administered radioactive substance.
Of particular interest are studies on clearance of endogenous
substances such as asialoglycoproteins. These studies reflect the
liver's established ability to remove natural asialoglycoproteins
from the circulation. In a variety of liver disease states,
asialoglycoprotein levels have been shown to be elevated,
indicating a decrease in asialoglycoprotein receptor activity.(41)
However, changes in synthetic rates of these proteins must also be
determined, in order to interpret actual clearance values, making
these parameters cumbersome to use as a measure of hepatic
function. A final undesirable aspect of these tests is that they
involve exposure of the subject/patient to radioactivity. The use
of radioactivity also makes the tests more labor intensive to
perform than non-radioactive tests. Finally, only single
measurements can be made at a time without involving tedious
separation of multiple .sup.14C labeled compounds.
[0166] Although these currently available tests can provide useful
information, all share common weaknesses. Hepatic failure is
ultimately dependent on the number of functional hepatocytes
present in a given disease state. Current testing methodology is
based upon indirect measurements of hepatocyte viability. Direct
measurement of hepatocyte activity based upon biological activities
such as receptor activity are not commercially available. A
hepatocyte directed agent using stable isotope labeling and neutron
activation that is an embodiment of the invention, offers the
prospect of overcoming this limitation of current diagnostic
procedures.
Liver Receptors and Liver Receptor Based Agents.
[0167] Much of the technology associated with receptor based
diagnostic agents has been in fields associated with MR and SPEC
imaging. This technology was developed to measure the distribution
of agents that reflect organ function. However, an agent to measure
passive distribution in the extracellular space would be desirable
for detection of liver lesions.
[0168] One class of such compounds are iron chelates that appear to
be absorbed by hepatocytes by an unknown biochemical mechanism. An
iron derivative has been reported to achieve significant MR signal
changes in liver tissue in dogs and rats.(42) However, application
of FE-EHPG as a liver contrast agent suffers from two problems. (i)
Uptake into liver is inefficient, as only 6% of an administered
dose is adsorbed by the liver. (ii) The dose per kilogram of
Fe-EHPG needed to achieve liver contrast in rats is 4 to 5 times
greater than the currently established level which is an upper
limit for its use in humans.(42)
[0169] Another class of MR agent, gadolinium-EOB-DTPA, has been
used to measure the kinetics of hepatic uptake and biliary
excretion. Liver accumulation results from its fast transport into
hepatocytes and rate-limited slower transport into bile.
Accumulation against a strong concentration gradient suggests an
energy dependent transport into hepatocytes, although its mechanism
of transport has not been determined.(43)
[0170] Ferrite particles have been used as a contrast agent for
liver imaging.(44) These commercially available micron sized
particles are taken up by the Kupffer cells of liver, and produce
effective signal modulation. In recognition that the Kupffer cell
may not be the optimal target for hepatic contrast agents, however,
a variety of asialoglycoprotein receptor-specific agents (ASGP-R)
agents have been developed.
[0171] Other assays of liver health and regeneration have been
based on epidermal growth factor receptor,(45) LDL receptor
gene,(46) laminin-hepatocyte affinity,(47) insulin-like growth
factor-II/mannose 6-phosphate receptor,(48) and atrial natiuretic
hormone receptor.(49) These preliminary reports require
confirmation and further development before use in humans.
Targeting Materials into Hepatocytes Via the Asialoglycoprotein
Receptor (ASGP-R).
[0172] Receptor-mediated endocytosis via the ASGR-R can rapidly
remove from circulation a variety of macromolecules that have a
terminal galactose. When such a galactose containing macromolecule
is coupled to another moiety of widely differing chemical
properties and molecular weight, such a product can rapidly enter
hepatocytes via the ASGP-R. These moieties include radioactive
isotopes such as technetium 101, and iodine drugs, N-acetyl
cysteine, araAMP, and DNA.(50).
[0173] ASGP-R have the ability to take up galactose terminated,
protein coated ferrite particles in vivo.(51) These particles are
taken up preferentially by hepatocytes (70%) and largely avoid
uptake by the reticulo-endothelial system (RES). After uptake by
hepatocytes, vesicles containing ferrite are magnetically isolated
and the proteins of the vesicles are analyzed. For crystal based
ferrite material to bind the ASGP-R of hepatocytes, it must
penetrate pores of the 100 nm fenestrae characteristic of
endothelial cells that lie between the hepatocyte and the
circulatory compartment. Particles smaller than 100 nm are needed
to serve as hepatocyte directed diagnostic agents.
[0174] Josephson et al. synthesized a functionalized
superparamagnetic iron oxide colloid (.about.50 nm) coated with the
polygalactosylated polysaccharide arabinogalactan. This colloid is
rapidly cleared from the vascular system, and clearance is
inhibited by asialofetuin but not by fetuin. The particles are
taken up by hepatocytes to an extent greater than 90%. This agent
was used as an effective magnetic resonance imaging agent based on
its receptor mediated endocytosis through the ASGP-R. Imaging
studies using this agent clearly distinguished between normal liver
tissue (where the agent was taken up) and liver tumors (where the
agent was not taken up; 52, 60). Leveille-Webster et al. used this
agent to measure changes in ASGP-R biology during liver
regeneration and endotoxemia in rats.(53)
[0175] Vera et al. synthesized a gadolinium complex of
polydiethylenetriamine pentaacetic acid polyneogalactosyl
polylysine which was tested as a paramagnetic contrast agent for
MRI of the liver.(54) The agent performed similarly to the
arabinogalactan coated superparamagnetic iron oxide of Josephson et
al.(60) No further reports of the Vera agent have appeared.
[0176] Receptor studies that rely on MR contrast agents are of
limited general usefulness because MR imagers are expensive and
only a few are available, and application of colloidal MR contrast
agents in clinical practice and radiology has not been widely
accepted due to cost factors. Further, there is a general
perception that colloidal materials used at the concentrations
needed for MR imaging elicit adverse reactions in humans.
[0177] The most thoroughly studied class of receptor directed
agents comprise galactosylated albumin (NGA) labeled with
.sup.99mTc. A radioactive hepatocyte directed contrast agent was
developed (54) that differs from previous colloidal liver contrast
agents in that it is taken up specifically by hepatocytes via the
ASGPR. The agent has galactose groups attached to albumin, and the
glycoprotein is labeled with radioactive technetium. The resulting
material is technetium labeled neoglycoalbumin or .sup.99mTc-NGA.
Technetium sulfur colloid and .sup.99mTc-NGA provide different
images of the liver using scintigraphic techniques.(54)
.sup.99mTc-NGA has been used also to study blood clearance and
hepatic uptake in normal rats and rats with chloroform induced
chronic injury; a quantitative model has been developed in normal
humans and patients with cirrhosis, to assess hepatic blood flow
and hepatic receptor binding; the utility of .sup.99mTc-NGA for
assessing functioning mass of the liver has been studied.(55) Other
investigators using a combination of blood studies and scintigraphy
have reported similar findings with .sup.99mTc-NGA.(55, 56)
[0178] However, use of .sup.99mTc-NGA in the study of liver biology
in the research laboratory and the clinic is limited. In research,
many investigators have little access to molybdenum/technetium
generators, and avoid the use of radioactivity. In the clinic,
radioactivity presents a potential hazard to the patient and
medical personnel. Scintigraphy relies upon expensive
instrumentation, long times of contact between patients and health
care workers, and high expense. Use of a single radioactive labeled
receptor directed compound such as .sup.99mTc-NGA does not permit
multiple and simultaneous measurements of a plurality of activities
of different receptors.
[0179] Better methods to measure hepatic receptor function can aid
clinical hepatology both for diagnostic or for prognostic purposes.
The development of reliable diagnostic agents and methods to
measure functions of receptors in experimental subjects that are
cost effective, easy to use and can be safely repeated in patients
and research subjects to monitor their response to therapeutic
intervention, will have clear advantages over existing methods.
Embodiments of the invention provide nonradioactive methods to
directly measure single or multiple hepatic receptor activities in
research subjects and in humans, an approach will be less labor
intensive and less expensive compared to current techniques.
[0180] Stable isotope labeling offers a cost effective and
technologically feasible approach to dealing with medical needs for
multiple receptor measurements and is a current technically
feasible solution. Non-radioactive, non-toxic agents, directed to
the asialoglycoprotein receptor of hepatocytes by galactose, can be
rapidly and specifically removed from the blood as a function of
the number of active receptors in the liver. Kinetic modeling of
blood depletion of these agents can estimate the number of
functioning receptors in the liver. Receptor targeted diagnostic
agents, combined with stable isotope labeling and neutron
activation, represent a technologically novel general approach to
design of agents to measure receptor function in the liver and
other organs. Most importantly, stable isotope labeling offers an
opportunity to measure multiple receptor activities simultaneously.
Other important examples of receptor mediated endocytosis include
the transferrin receptor, the low density lipoprotein (LDL)
receptor, the mannose 6-phosphate receptor and the mannose
receptor.
Application of Stable Isotope Labeling and Neutron Activation to
Simultaneous Measurement of Multiple Activities.
[0181] Simultaneous measurement of multiple receptor directed
agents using stable isotopes and neutron activation is potentiated
by diagnostic agents provided herein, biodistribution of which is
determined by the ability of these agents to bind to cell surface
receptors. This approach applied to measuring liver function and
health is described above. The application to measuring other organ
receptor activities, and simultaneous measuring receptors from
multiple organ systems can be achieved using the concepts presented
above for hepatocytes.
Application of Stable-Isotope Labeling and Neutron Activation to
the Measurement of Other in Vivo Tests.
[0182] Three classes of stable isotope labeled compounds illustrate
this technique for measurement of biological functions: (i) low
molecular weight compounds (<5000 kDa) represented by chelates
of rare earth atoms and chelates of bile acids; (ii) high molecular
weight compounds (>5000 kDa) represented by chelates of
polysaccharides and proteins; and (iii) colloids. Proteins used
herein can be pegylated, i.e., chemically modified by addition of
polyethylene glycol (PEG) molecules, to improve characteristics
such as stability. PEG addition produces proteins that remain
non-toxic and are amphophilic, soluble in water and most organic
solvents. Pegylation is achieved via stable covalent bonds between
an amino or sulphydryl group of the protein, and a chemically
reactive group on the PEG. The reaction can be controlled by
procedures known to one of ordinary skill in the art of protein
chemistry, giving proteins with a chosen extent of pegylation.
Examples of these compounds are presented herein for measuring
renal and hepatic function. The application of this technique is
not limited by use of a single isotope nor is it limited by the use
of labeled compounds of similar molecular weight. A plurality of
labeled compounds of varying molecular weight may be combined for
administration to a subject, to obtain information simultaneously
about multiple organ functions and multiple functions within a
single organ. The examples of these compounds in the examples below
are for purposes of illustration and specific teaching, and should
not be construed to limit application of such compounds or other
compounds of similar nature and molecular weight. Examples of the
application of this technology for the measurement of biological
functions are listed in Table 2. TABLE-US-00003 TABLE 2
Applications of neutron activation and stable isotope labeling for
the detection of xenobiotic compounds for measurement of
physiological functions and compound biodistribution. Organ system
and function Typical compound Renal Glomerular filtration rate
Sm-DTPA, iohexol Glomerular integrity rate Sm Ficoll Hepatic Bile
acids Lu-chelate of cholic acid Low density lipoprotein
SCN-Bz-DOTA-chelate of La - low density lipoprotein Transferrin
biodistribution .sup.58Fe-transferrin Transferrin receptor
.sup.58Fe-transferrin activity Asialoglycoprotein receptor
Arabinogalactan coated activity gold colloid Ferritin
.sup.58Fe-ferritin Pulmonary Transpulmonary drug
SCN-Bz-DOTA-chelate delivery of La peptide Intestinal transfer
Intestinal transit Albumin coated gold colloid Intestinal-blood
transit Sm-oxide colloid coated with silane Lymphatics
.sup.58Fe-labeled iron oxide colloid Measurement of fluid volumes
in different body fluid compartments Application of the
SCN-Bz-DOTA-chelate indicator-dilution principle of La -albumin
Extracellular fluid volume Na, Cl, Br Plasma volume Human-DTPA-Sm
Albumin
[0183] Embodiments of the invention are further illustrated by the
following Examples. In one example, a method of determining the
glomerular filtration rate of a subject comprises [1] obtaining a
serum sample S.sub.pre and a urine sample U.sub.pre from a subject;
[2] administering to the subject an amount of a stable-isotope
labeled substance that is filtered by the kidneys and is readily
detectable by neutron activation in serum and urine; [3] allowing
for the concentration of the substance to equilibrate between the
blood and the extravascular spaces; [4] separating an aliquot of
the urine sample v.sub.A and obtaining a serum sample from the
subject at the time t.sub.A; [5] calculating a urine rate
(v/a).sub.A from the formula (v/a).sub.A=V.sub.A/a.sub.A; [6]
measuring the concentrations of stable isotope in the serum and
urine samples by neutron activation analysis; and [7] calculating
GFR from the formula GFR = i = 1 p .times. .times. 2 .times. [ SI ]
U i + 1 .times. v i + 1 .times. / .times. ( [ SI ] S i + [ SI ] S i
+ 1 ) .times. / .times. p ##EQU2##
[0184] Methods are also presented for measuring bile acid movement
throughout the body and for measuring receptor activity.
[0185] More generally, methods are presented wherein the
concentration of multiple stable-isotope labeled compounds may be
determined simultaneously in living subjects and their excretory
products by in vitro measurements using neutron activation.
Compositions containing single or multiple normal-abundance
stable-isotope labeled compounds, and compositions containing
single or multiple enriched stable isotope labeled compounds and
compositions are described.
[0186] These compositions may be determined individually or
simultaneously in living subjects and their excretory products, by
in vitro measurements using neutron activation. In embodiments, the
invention provides a method for in vitro evaluation of the
clearance rate or concentration of either naturally occurring
compounds which contain certain stable-isotopes, or xenobiotics
bearing certain stable-isotopes administered to and subsequently
assayed in samples obtained from a living subject, thereby
providing a noninvasive method for determining parameters
exemplified by [1] the blood volume, [2] the status of the
excretory organs of the subject, and [3] a proper dosing regimen of
a pharmacologically active compound to be administered to the
subject.
[0187] The invention having now been fully described, the examples
below are presented to illustrate various embodiments in detail,
and do not to limit the scope of the invention. References cited
are hereby incorporated by reference herein.
EXAMPLES
General Procedure of Measuring Blood Clearance
[0188] The method of the invention may be used to monitor the blood
clearance mechanisms mediated by, for example, liver receptors and
kidney function of a subject/patient and thereby provide
information regarding the functioning of these mechanisms. Test
substances designed to assess organ function, each labeled with a
stable isotope may be injected into a subject either as a bolus or
a constant infusion. In general, the expected relationships between
test substance blood concentration as a function of time are shown
in FIG. 3 (bolus injection) and 4 (constant infusion). FIG. 3
illustrates that, following a bolus injection of the test compound,
the blood concentration of the test compound increases sharply, and
then decreases over time until reaching its preinjection
concentration in a normal subject. When organ impairment (e.g.
kidney failure) occurs, the blood concentration of the test
compound will decrease more slowly and take a longer time to reach
preinjection levels than with normal organ function. In rare cases,
organ function may be increased compared to normal function, in
which case test substance blood concentration will decline more
rapidly than in a normal subject.
[0189] FIG. 4 illustrates that, following a constant infusion of
the test compound, the measured blood concentration of the test
compound increases sharply, and then becomes constant for a normal
patient at steady state where the excretion rate equals the rate of
infusion. When organ impairment (e.g. kidney failure) occurs, the
value of test compound will continue to increase over time.
[0190] Having now generally described applications that are
embodiments of this invention, embodiments will be better
understood by reference to certain specific examples, which are
included herein for purposes of illustration only and are not
intended to be limiting of any embodiment thereof, unless so
specified.
[0191] Examples 1-6 show the addition of stable isotope to sample
tubes for monitoring and correcting for neutron flux variation in
each sample tube. Example 6 demonstrates chemical bar coding, used
to assign lot numbers to sample tubes.
[0192] Examples 7-36 relate to the measurement of glomerular
filtration rate (GFR) using stable isotopes. Examples 7 through 25
illustrate the formation of various chelates of natural abundance
stable isotope metals. The examples show two chelates and three
stable isotopes.
[0193] Examples are presented to demonstrate that gadolinium
chelates detected by NMR properties or atomic absorbance, and
various stable isotope chelates detectable by neutron activation,
have nearly identical properties with respect to: chelate formation
(Examples 20-21; 26-27); stability (Examples 20-21; 26-27); charge
as reflected by their chromatography on a cation chromatographic
support (Examples 16-19; 24-25); and biological properties as
indicated by blood excretion and urine accumulation (Examples
29-30).
[0194] Example 28 illustrates the formation of various chelates of
stable isotope metals using enriched abundance of the stable
isotopes of the various elements. The similarity of chelate
formation, chromatography and stability between corresponding pairs
of natural and enriched abundance can be seen by comparing
respective data from corresponding Examples. The only difference
between the pairs of chelates is that the enriched isotope member
is proportionately more detectable based on the increased
proportion of the stable isotope.
[0195] Examples 29 through 33 show the kinetics of blood depletion
and urine accumulation of stable isotope labeled chelates in the
rat. The results show the near identical properties of gadolinium
chelates detected by NMR properties or atomic absorbance and
various stable isotope chelates detectable by neutron activation.
The similarity of the two types of chelates regarding formation of
chelates, stability of chelates, and chromatography (i.e., based on
charge) of the chelates is shown.
[0196] Example 36 represents the results of a study measuring the
GFR in a rabbit model using iohexol as the low molecular weight
compound bearing a stable isotope, in this case 1271. The results
are consistent with previous reports using a variety of other
methods and compounds to measure GFR.
[0197] Example 37 represents the results of a hypothetical study in
humans, comparing GFR measured using Sm-DTPA (determined by neutron
activation) with two other methods (.sup.99mTc-DTPA and Gd-DTPA).
Based on the near identical physical, chemical and biological
properties of the three chelates, identical GFR measurements for
the three compounds in humans are expected.
[0198] The following examples provide data on human glomerular
filtration rates (GFR) obtained by practicing a method of this
invention that relies on the measurement of the clearance of
Sm-DTPA and Gd-DTPA (Magnevist, Berlex Laboratories) from the serum
and urine of a patient. Results obtained from 35 patients show good
correlation with GFR rates determined by prior art methods such as
the .sup.99mTc-DTPA clearance test.
[0199] Examples 38-51 relate to Glomerular Sieving Assays
(Glomerular Integrity Rate). Examples are presented for Ficoll, and
similar chemistry can be effected using other polysaccharides, such
as dextran and pullulan. Examples are also presented for protein
labeling with stable isotopes for applications in Glomerular
Sieving Assays.
[0200] Examples 52-55 show assays of formation of stable isotope
labeled chelate and stability of labeled Ficoll and inulin.
[0201] Example 56 illustrates the use of multiple stable isotope
labeled compounds to perform multiple bioassays simultaneously.
[0202] Examples 57 through 62 illustrate labeling of low molecular
weight molecules with stable isotope metals. The examples
demonstrate the application of bile acids for measuring liver
function. The examples are presented merely to exemplify labeling
low molecular weight compounds for measuring biological functions,
and are in no way intended to limit the scope of the present
claims.
[0203] Example 63 shows the results of a hypothetical study in
humans comparing the clearance rate of stable isotope labeled
Sm-cholic acid and radiolabeled cholic acid in patients with
Laennec's cirrhosis and in healthy subjects. Based on the similar
physical, chemical and biological properties of these agents, data
showing identical clearance rates in humans are expected. The
example provides data on human bile acid clearance rates obtained
by practicing a method that is an embodiment of this invention that
relies on measurement of the clearance of Sm-cholic acid from the
serum of patients. Results obtained from 16 patients show good
correlation with clearance rates determined by prior art methods
such as .sup.14C-cholic acid clearance test.
[0204] Example 64 shows the results of a hypothetical study in
humans comparing the clearance rate of Sm-taurocholic acid (Sm-TCA)
and radiolabeled .sup.75Se-homocholic acid taurine (.sup.75SeHCAT),
a synthetic analog of taurocholic acid, in patients with diarrhea
of unknown cause. Based on the similar physical, chemical and
biological properties of these agents, observation of identical
clearance rates in humans is expected. The following examples
provide data on human bile acid clearance rates obtained by
practicing the method of this invention that relies on the
measurement of the clearance of Sm-TCA from the stool of patients.
Results obtained from 20 patients show good correlation with
clearance rates determined by prior art methods, such as
.sup.75SeHCAT assayes.
[0205] Examples 65-68 illustrate the synthesis of colloids labeled
with stable isotopes. Results similar to Examples 65 and 66 may be
obtained by substituting other polysaccharides such as dextran,
starch, hydroxyethyl starch, pullulan and other similar polymers
for arabinogalactan, whereby one can obtain colloids labeled with
stable isotopes and having different surface properties.
[0206] Example 69 shows the measurement of receptor activity using
colloidal gold coated with a plurality of galactose moities.
Example 1
Post Labeling Sample Tubes with Monitor (Use of an Internal
Standard to Correct for Neutron Flux Variation Between Samples)
[0207] This example illustrates the procedure for the use of an
internal monitor to correct for neutron flux variation between
sample tubes.
[0208] Tubes containing samples of samarium (10 .mu.g), lutetium
(10 .mu.g), gold (10 .mu.g) and arsenic (1 .mu.g) for neutron
activation were prepared by pipetting 100 .mu.l of an aqueous
solution of samarium, lutetium, and gold chloride and 25 .mu.l of
lithium arsenate-hexafluride into the bottom of each tube. The
water was removed by heating the tubes at 70.degree. C. for 12
hours. The tubes were exposed to a 2 megawatt neutron flux for 15
minutes. Five days later the tubes were counted for three minutes.
Column 1 and 2 of Table 3 show the disintegrations per minute (dpm)
and the correction factor calculated for the arsenic monitor. Since
identical amounts of arsenic were added to each tube, all counts
should be identical except for variation in neutron flux between
tubes. An ideal count rate of 27984 was assumed and the correction
factor (Column 2) is obtained by dividing each dpm of column 1 into
27984. Columns 3 through 8 show the dpm measured for 20 identical
samarium, lutetium, and gold samples, respectively, before and
after correction for neutron flux. For instance, column 4 is
obtained by multiplying Column 3 by the factor in Column 2. The
standard deviation and coefficient of variation for each set of
data are shown at the bottom of each Column. Significant
improvement in the between sample dpm values for tubes corrected
for neutron flux was observed. TABLE-US-00004 TABLE 3 Use of an
arsenic monitor as an internal standard (in dpm except for
correction factor) Arsenic Correction Samarium Gold Lutetium
monitor factor Uncorrected Corrected Uncorrected Corrected
Uncorrected Corrected 27984 1.000 1836720.0 1836720.0 2222340.0
2222340.0 716520.0 716520.0 30530 0.917 2057460.0 1885881.4
2508480.0 2299289.4 813180.0 745366.2 27346 1.023 1803420.0
1845495.0 2178900.0 2229735.2 715200.0 731886.1 33311 0.840
2141880.0 1799356.7 2669520.0 2242618.0 839100.0 704913.5 20189
1.386 1325460.0 1837221.9 1578960.0 2188598.6 503490.0 697888.2
35077 0.798 2339040.0 1866057.4 2841840.0 2267185.1 913020.0
728396.1 41825 0.669 2787780.0 1865229.8 3412560.0 2283253.5
1075080.0 719307.6 32157 0.870 2110380.0 1836516.9 2553420.0
2222063.8 825780.0 718618.9 29882 0.936 2000640.0 1873566.4
2426640.0 2272508.3 790140.0 739953.1 49091 0.001 3242220.0
1848206.1 4031100.0 2297901.9 1233480.0 703137.1 42308 0.661
2797320.0 1850245.9 3421800.0 2263298.9 1110540.0 734550.2 44733
0.626 2940120.0 1839275.7 3656700.0 2287552.7 1140840.0 713684.9
44638 0.627 2986740.0 1872416.6 3649800.0 2288095.4 1146540.0
718777.2 37048 0.755 2450700.0 1851122.6 2951400.0 2229323.5
928440.0 701292.0 42363 0.661 2895300.0 1912567.0 3343320.0
2208518.4 1118160.0 738630.2 49074 0.570 3309240.0 1887063.9
4076460.0 2324564.1 1261620.0 719427.3 33246 0.842 2358240.0
1984990.3 2797860.0 2355029.6 953160.0 802298.9 42209 0.663
2845260.0 1886369.2 3400980.0 2254804.1 1072500.0 711053.1 45029
0.621 2980260.0 1852130.8 3687000.0 2291345.8 1106820.0 687851.2
45244 0.619 2965800.0 1834385.7 3685020.0 2279232.6 1196220.0
739877.6 45676 0.613 3025320.0 1853501.9 3673080.0 2250360.6
1140780.0 698913.8 2533300.0 1862777.2 3084151.4 2264648.5 980981.4
722492.5 528328.8 36336.3 661646.1 39201.1 197789.8 23719.8 20.85
1.95 21.45 1.73 20.16 3.28
Example 2
Effect of Placement of Monitor in Various Locations within the
Sample Tube when Used to Correct for Sample Count Rate
[0209] This example illustrates the importance of locating neutron
flux monitor in identical portions within each tube, and counting
each tube with the same geometry.
[0210] A sample of 100 .mu.l of arsenic monitor containing, for
example, 10 .mu.g As is added to each of three tubes, at the bottom
of the tube (tube 1), the middle of the tube (tube 2), or in the
cap of the tube (tube 3). The water is removed by heating at
70.degree. C. allowing the monitor to be deposited as a dry film.
Next, 100 .mu.l of samarium (10 ng) is added to the bottom of each
tube without disturbing the monitor and the water is removed by
heating. Samarium and arsenic solutions are prepared as in Example
1. The three tubes are taped together and exposed to a 1 megawatt
neutron flux for 15 minutes. Since the sample tubes are close
enough together to assure that neutron flux is experimentally
constant across the three tubes, all tubes receive the same level
of neutron flux. Three days later the tubes are counted for three
minutes by placing the bottom of each tube on the surface of the
detector face. Results are shown in Table 4.
[0211] The correction factor (Column 2 and its application to
Column 3 to yield Column 4 are obtained as described in Example 1.
TABLE-US-00005 TABLE 4 Effect of locating neutron flux monitor in
the different position within sample tubes on the apparent dpm
produced by a constant amount of samarium located in the same
position in the sample tubes. The experiment was performed as
described in Example 2. Arsenic Samarium Samarium Monitor
uncorrected for corrected for (location) Correction neutron flux
neutron flux dpm factor Dpm dpm 1152 0.868 5625 4882 (bottom) 853
1.172 5657 6630 (middle) 647 1.546 5583 8631 (top)
Example 3
Pre-Labeling Sample Tubes with Arsenic Monitor (Internal Standard
to Correct for Neutron Flux Variation Between Samples)
[0212] This example illustrates the technical advantage obtained by
placing monitor in the sample tube before placing sample in the
tube. This assures that the monitor is located in the same position
within each tube. Second, the monitor is placed in the tube before
the tube is supplied to the customer reducing the need to handle
sample tubes upon receiving them for neutron activation.
[0213] Sample tubes were labeled with arsenic (an example of an
stable isotope that can serve as an internal monitor) by dissolving
10 mg of lithium hexafluoroarsenate in 100 ml of water soluble
polyurethane and pipetting 50 .mu.l of the mixture into each tube.
The contents were added to each tube to assure location at the
bottom of the tube. The tube contents were solidified by air drying
at room temperature for five days.
Example 4
Pre-Labeling Sample Tubes with Samarium Monitor (Internal Standard
to Correct for Neutron Flux Variation Between Samples)
[0214] Sample tubes are labeled with samarium (an example of an
stable isotope that can serve as an internal monitor) by dissolving
5 mg of samarium-DTPA in 100 ml of water soluble polyurethane and
pipetting 50 .mu.l of the mixture into each tube. The contents are
added to or provided in each tube such that maintaining the
contents at a location at the bottom of the tube is assured. The
tube contents are solidified by air drying at room temperature for
five days.
Example 5
Pre-Labeling Sample Tubes with Iridium Monitor (Internal Standard
to Correct for Neutron Flux Variation Between Samples)
[0215] Sample tubes are labeled with iridium (an example of an
stable isotope that can serve as an internal monitor) by dissolving
10 mg of iridium-DTPA in 100 ml of 0.1. % aqueous polyvinyl alcohol
and pipetting 50 .mu.l of the mixture into the cap of each tube.
The contents are added to or provided in each tube such that
maintaining the contents at a location at the top of the tube is
assured. The tube contents are solidified by drying at 80.degree.
C. for 8 hours.
Example 6
Chemical Bar Coding Using Stable Isotopes
[0216] In this illustrative example sample tubes are pre-labeled
with arsenic (as internal monitor) and varying amounts of bromine
and lanthanum to represent 10 lots of tubes. As can be seen in
Table 5, each lot allows discreet identification of the ten sets of
tubes by measuring the dpm of the three elements. By increasing the
range of dpms for bromine and lanthanum and by the addition of a
fourth element such as ytterbium, it is seen that a very large
number of tube lot labeling combinations can be established. Tubes
may be labeled with the various elements using methods described in
Examples 3-5. TABLE-US-00006 TABLE 5 Identification of tubes by
chemical bar coding using multiple stable isotope. Arsenic Bromine
Lanthanum Lot # Dpm Ytterbium 1 1000 500 1000 0 2 1000 1000 1000 0
3 1000 1500 1000 0 4 1000 2000 1000 0 5 1000 2500 1000 0 6 1000 500
2000 0 7 1000 1000 2000 0 8 1000 1500 2000 0 9 1000 2000 2000 0 10
1000 2500 2000 0
Example 7
Preparation of Reagents
[0217] Reagents were prepared as indicated in Table 6.
TABLE-US-00007 TABLE 6 Preparation of reagents Fill to final volume
with deionized Reagent Compound Source Amount water, ml Adjust pH
to with 0.01 MDTPA DTPA.sup.a SIGMA 393.5 mg 10 pH to 6.95 with
LiOH 0.1 M DOTA DOTA.sup.b Macrocylics 481 mg 10 pH to 7.8 with
LiOH CM.sup.c sephadex SIGMA 12 g 100 1M SaCl.sub.3 Samarium
Aldrich 3.6 g 10 6N HCl to dissolve chloride hexahydrate 1M
LaCl.sub.3. Lanthanum Aldrich 3.7 g 10 chloride, heptahydrate 1M
EuCl.sub.3. Europium Aldrich 3.7 g 10 chloride hexahydrate 1M
GdCl.sub.3 Gadolinium Aldrich chloride 1 M Tris Trizma base SIGMA
12.11 g 100 7.5 with 12 N HCl buffer 0.01 M Tris 1 M Tris buffer 1
ml 99 buffer .sup.aDTPA stands for diethylenetriamine pentaacetic
acid. .sup.bDOTA stands for tetraazacyclododecanetetraacetic acid.
.sup.cCM stands for carboxymethyl.
Example 8
Preparation of 1 mM Gd-DTPA Chelate and 1 mM GdCl.sub.3
[0218] Preparation of chelate of gadolinium and DTPA. To a 15 ml
plastic centrifuge tube add in the following order: 1 ml of 1M Tris
buffer pH 7.5, 0.11 ml of 0.1 M DTPA (pH 6.5), 0.01 ml of 1 M
GdCl.sub.3 and 9 ml deionized water. Contents are mixed, and
incubated about 5 to about 45 minutes (for example, about 30
minutes) at room temperature. The pH of the solution was 7.52.
[0219] Preparation of Gadolinium chloride solution. To a 15 ml
plastic centrifuge tube add the following order: 1 ml of 1M Tris
buffer pH 7.5, 0.01 ml of 1M GdCl.sub.3 and 9 ml water. Contents
are mixed, and incubated 30 to 45 minutes at room temperature. The
pH of the solution was 7.54.
Example 9
Preparation of 1 mM Sm-DTPA Chelate and 1 mM SmCl.sub.3
[0220] Preparation of chelate of samarium and DTPA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DTPA (pH 6.5), 0.01
ml of 1 M 5 mCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.52.
[0221] Preparation of samarium chloride solution. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.01 ml of 1M SmCl.sub.3 and 9 ml
water. Contents are mixed, and incubated 30 to 45 minutes at room
temperature. The pH of the solution was 7.54.
Example 10
Preparation of 1 mM La-DTPA Chelate and 1 mM LaCl.sub.3
[0222] Preparation of chelate of lanthanum and DTPA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DTPA (pH 6.5), 0.01
ml of 1 M LaCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.52.
[0223] Preparation of lanthanum chloride solution. To a 15 ml
plastic centrifuge tube were added in the following order: 1 ml of
1M Tris buffer pH 7.5, 0.01 ml of 1M LaCl.sub.3 and 9 ml water.
Contents are mixed, and incubated 30 to 45 minutes at room
temperature. The pH of the solution was 7.5.
Example 11
Preparation of 1 mM Eu-DTPA Chelate and 1 mM EuCl.sub.3
[0224] Preparation of chelate of europium and DTPA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DTPA (pH 6.5), 0.01
ml of 1 M EuCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.52.
[0225] Preparation of europium chloride solution. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.01 ml of 1M EuCl.sub.3 and 9 ml
water. Contents are mixed, and incubated 30 to 45 minutes at room
temperature. The pH of the solution was 7.5.
Example 12
Preparation of 1 mM Gd-DOTA Chelate
[0226] Preparation of chelate of gadolinium and DOTA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1 M Tris buffer pH 7.5, 0.11 ml of 0.1 M DOTA (pH 7.8),
0.01 ml of 1 M GdCl.sub.3 and 9 ml deionized water. Contents are
mixed, and incubated 5 to 45 minutes (for example, 30 minutes) at
room temperature. The pH of the solution was 7.5.
Example 13
Preparation of 1 mM Sm-DOTA Chelate
[0227] Preparation of chelate of samarium and DOTA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DOTA (pH 7.8), 0.01
ml of 1 M SmCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.5.
Example 14
Preparation of 1 mM La-DOTA Chelate
[0228] Preparation of chelate of lanthanum and DOTA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DOTA (pH 7.8), 0.01
ml of 1 M LaCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.5.
Example 15
Preparation of 1 mM Eu-DOTA Chelate
[0229] Preparation of chelate of europium and DOTA. To a 15 ml
plastic centrifuge tube reagents were added in the following order:
1 ml of 1M Tris buffer pH 7.5, 0.11 ml of 0.1 M DOTA (pH 7.8), 0.01
ml of 1 M EuCl.sub.3 and 9 ml deionized water. Contents are mixed,
and incubated 5 to 45 minutes (for example, 30 minutes) at room
temperature. The pH of the solution was 7.5.
Example 16
Assay of Gd-DTPA Chelate
[0230] Preparation of carboxymethyl sephadex column. To two 10 ml
plastic pipets cut off at the 3 ml mark and plugged with glass wool
at the bottom add enough slurry to form a 2 ml volume of the CM
sephadex. Wash the packed resin with 6 ml of 1 M Tris buffer pH
7.5, and 6 ml of 0.01M Tris buffer pH 7.5. Dilute samples (1:10)
(gadolinium-DTPA or gadolinium chloride) from Example 8 with
distilled water (0.2 ml to 2 ml). Collect the eluants of fractions
as follows. Fraction 1.3 ml of 0.01 M Tris buffer pH 7.5 and allow
to drain into column. Fraction 2.1 ml of sample (gadolinium-DTPA or
gadolinium chloride) and allow to drain into column. Apply 3 ml of
0.01 M Tris buffer pH 7.5 and allow to drain into column. Fraction
3.3 ml of 0.01M Tris buffer pH 7.5 and allow to drain into column.
Dry all fractions at 70.degree. C. for 76 hours, dissolve in 1 ml
of 1 mM HCl and assay by atomic absorption. TABLE-US-00008 TABLE 7
Assay of Gd-DTPA chelate Fraction # Fraction description % of total
Gadolinium-DTPA from Example 8 1 3 ml of 0.01M Tris buffer pH 7.5 0
2 1 ml of diluted Gd-DTPA from Example 8 100 diluted 1:10 followed
by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH
7.5 0 Gadolinium chloride from Example 8 1 3 ml of 0.01M Tris
buffer pH 7.5 0 2 1 ml of GdCl.sub.3 from Example 8 diluted 1:10 0
followed by 3 ml of 0.01M Tris buffer pH 7.5 1 3 3 ml of 0.01M Tris
buffer pH 7.5 0
[0231] Results: Table 7 shows that 100% of Gd-DTPA is eluted from
the CM-Sephadex column as expected for a negatively charged
molecule. In contrast, 100% of unchelated Gd.sup.+3 is retained on
the column as expected for a positive ion. These results
demonstrate that the DTPA chelate of Gd.sup.+3 forms within 5
minutes, and that this method can be used to ascertain the
formation of metal DTPA chelates.
Example 17
Assay of Sm-DTPA Chelate
[0232] Preparation of carboxymethyl Sephadex column. To two 10 ml
plastic pipets which had been cut off at the 3 ml mark and plugged
with glass wool at the bottom, enough slurry was added to form a 2
ml volume of the CM Sephadex. The packed resin was wash with 6 ml
of 1 M Tris buffer pH 7.5, and 6 ml of 0.01M Tris buffer pH 7.5.
The samples prepared in Example 9 (samarium-DTPA or samarium
chloride) were diluted 1:10 with distilled water (0.2 ml to 2 ml).
Fractions were applied as follows. Fraction 1. Three ml of 0.01 M
Tris buffer pH 7.5 and allow to drain into column. Fraction 2. One
ml of sample (samarium-DTPA or samarium chloride) and allow to
drain into column. Apply 3 ml of 0.01 M Tris buffer pH 7.5 and
allow to drain into column. Fraction 3. Three ml of 0.01M Tris
buffer pH 7.5 and allow to drain into column. Collect the eluant of
fractions 1 through 3. Fraction 4. Column and contents. All
fractions were dried at 70.degree. C. for 76 hours and 25 .mu.l of
arsenic internal standard was added. Samples were activated by
exposure to a neutron flux in a 2 megawatt reactor for 15 minutes.
After three days each sample was counted for 3 minutes.
TABLE-US-00009 TABLE 8 Assay of Sm-DTPA chelate Samarium-DTPA from
Example 9 Fraction # Fraction description dpm % of total 1 3 ml of
0.01M Tris buffer pH 7.5 0 0 2 1 ml of diluted Sm-DTPA 1482087 97
from Example 9 diluted 1:10 followed by 3 ml of 0.01M Tris buffer
pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 19089 1 4 Column and
contents 24257 2 Samarium chloride from Example 9 Fraction # Sample
description dpm % of total 1 3 ml of 0.01M Tris buffer pH 7.5 0 0 2
1 ml of SmCl.sub.3 from 0 0 Example 9 diluted 1:10 followed by 3 ml
of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 0 0
4 Column and contents 1128598 100
[0233] Results: Table 8 shows that 98% of Sm-DTPA is eluted from
the CM-Sephadex column as expected for a negatively charged
molecule. In contrast 100% of unchelated Sm.sup.+3 is retained on
the column as expected for a positive ion. These results
demonstrate that the DTPA chelate of Sm.sup.+3 forms within 5
minutes, and that this method can be used to ascertain the
formation of metal DTPA chelates. These examples show that the DTPA
chelate of samarium and the DTPA chelate of gadolinium have
identical chromatographic behavior.
Example 18
Assay of La-DTPA Chelate
[0234] Preparation of carboxymethyl Sephadex column. To two 10 ml
plastic pipets which were cut off at the 3 ml mark and plugged with
glass wool at the bottom, enough slurry was added to form a 2 ml
volume of the CM Sephadex. The packed resin was washed with 6 ml of
1 M Tris buffer pH 7.5, and 6 ml of 0.01M Tris buffer pH 7.5. The
samples prepared in Example 10 (lanthanum-DTPA or lanthanum
chloride) were diluted 1:10 with distilled water (0.2 ml to 2 ml).
Fractions were applied as follows. Fraction 1. Three ml of 0.01 M
Tris buffer pH 7.5 and allow to drain into column. Fraction 2. One
ml of sample (lanthanum-DTPA or lanthanum chloride) and allow to
drain into column. Apply 3 ml of 0.01 M Tris buffer pH 7.5 and
allow to drain into column. Fraction 3. Three ml of 0.01 M Tris
buffer pH 7.5 and allow to drain into column. Collect the eluant of
fractions 1 through 3. Fraction 4. Column and contents. All
fractions were dried at 70.degree. C. for 76 hours, and 25 .mu.l of
arsenic internal standard was added. Samples were activated by
exposure to a neutron flux in a 2 megawatt reactor for 15 minutes.
After three days, each sample was counted for 3 minutes.
TABLE-US-00010 TABLE 9 Assay of La-DTPA chelate Lanthanum-DTPA from
Example 10 Fraction # Sample description dpm % of total 1 3 ml of
0.01M Tris buffer pH 7.5 0 0 2 1 ml of La-DTPA from 489692 100
Example 10 diluted 1:10 followed by 3 ml of 0.01M Tris buffer pH
7.5 3 3 ml of 0.01M Tris buffer pH 7.5 0 0 4 Column and contents 0
0 Lanthanum chloride from Example 10 Fraction # Sample description
DPM % of total 1 3 ml of 0.01M Tris buffer pH 7.5 0 0 2 1 ml of
LaCl.sub.3 from 0 0 Example 10 diluted 1:10 followed by 3 ml of
0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 0 0 4
Column and contents 254172 100
[0235] Results: Table 9 shows that 100% of La-DTPA is eluted from
the CM-Sephadex column as expected for a negatively charged
molecule. In contrast, 100% of unchelated La.sup.+3 is retained on
the column as expected for a positive ion. These results
demonstrate that the DTPA chelate of La.sup.+3 forms within 5
minutes. These examples show that the DTPA chelate of lanthanum and
the DTPA chelate of gadolinium have identical chromatographic
behavior.
Example 19
Assay of Eu-DTPA Chelate
[0236] Preparation of carboxymethyl Sephadex column. To two 10 ml
plastic pipets which were cut off at the 3 ml mark and plugged with
glass wool at the bottom, enough slurry was added to form a 2 ml
volume of the CM Sephadex. The packed resin was washed with 6 ml of
1 M Tris buffer pH 7.5, and 6 ml of 0.01M Tris buffer pH 7.5. The
samples prepared in Example 11 (europium-DTPA or Europium chloride)
were dilute 1:10 with distilled water (0.2 ml to 2 ml). Fractions
were applied as follows. Fraction 1. Three ml of 0.01 M Tris buffer
pH 7.5 and allow to drain into column. Fraction 2. One ml of sample
(Europium-DTPA or Europium chloride) and allow to drain into
column. Apply 3 ml of 0.01 M Tris buffer pH 7.5 and allow to drain
into column. Fraction 3. Three ml of 0.01M Tris buffer pH 7.5 and
allow to drain into column. Collect the eluant of fractions 1
through 3. Fraction 4. Column and contents. All fractions were
dried at 70.degree. C. for 76 hours and 25 .mu.l of arsenic
internal standard was added. Samples were activated by exposure to
a neutron flux in a 2 megawatt reactor for 15 minutes. After three
days each sample was counted for 3 minutes. TABLE-US-00011 TABLE 10
Assay of Eu-DTPA chelate Fraction # Sample description dpm % of
total Europium-DTPA from Example 11 1 3 ml of 0.01M Tris buffer pH
7.5 0 0 2 1 ml of Eu-DTPA from 22115 100 Example 11 diluted 1:10
followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris
buffer pH 7.5 0 0 4 Column and contents 0 0 Europium chloride from
Example 11 1 3 ml of 0.01M Tris buffer pH 7.5 0 0 2 1 ml of
EuCl.sub.3 from 0 0 Example 11 diluted 1:10 followed by 3 ml of
0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 0 0 4
Column and contents 21244 100
[0237] Results: Table 10 shows that 100% of Eu-DTPA is eluted from
CM-Sephadex column as expected for a negatively charged molecule.
In contrast 100% of unchelated Eu.sup.+3 is retained on the column
as expected for a positive ion. These results demonstrate that the
DTPA chelate of Eu.sup.+3 forms within 5 minutes. These data show
that the DTPA chelate of europium and the DTPA chelate of
gadolinium have identical chromatographic behavior.
Example 20
Stability of Gd-DTPA
[0238] The stability of gadolinium-DTPA to autoclaving is
demonstrated by properties of the pharmaceutical product known as
Magnevist.RTM..
Example 21
Stability of Sm-DTPA, La-DTPA, and Eu-DTPA to Autoclaving
[0239] A sample comprising 5 ml of Sm-DTPA, La-DTPA, and Eu-DTPA
prepared in Examples 9, 10, and 11 were placed in 10 ml glass
bottles, each capped with a grey butyl rubber cap, and the caps
were crimped. Samples were autoclaved for 30 minutes at 121.degree.
C. Samples were allowed to cool to room temperature and were
assayed as described in Examples 17, 18, and 19. TABLE-US-00012
TABLE 11 Assay of autoclaved Sm-DTPA chelate, La-DTPA chelate, and
Eu-DTPA chelate Fraction # Sample description dpm % of total
Samarium-DTPA AUTOCLAVED 1 5 ml of Sm-DTPA Example 9 was 1128928 98
autoclaved, 0.1 ml was diluted 1:10 and applied to the CM-Sephadex
column followed by 3 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 26387 2 3 Column and contents 1867 0
Lanthanum-DTPA AUTOCLAVED 1 5 ml of La-DTPA from Example 10 411400
97 was autoclaved, 0.1 ml was diluted 1:10 and applied to a
CM-Sephadex column followed by 3 ml of 0.01M Tris buffer pH 7.5 2 3
ml of 0.01M Tris buffer pH 7.5 12180 3 3 Column and contents 0 0
Europium-DTPA AUTOCLAVED 1 5 ml of Eu-DTPA from Example 11 380954
97 was autoclaved, 0.1 ml was diluted 1:10 and applied to a
CM-Sephadex column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3
ml of 0.01M Tris buffer pH 7.5 13226 3 3 Column and contents 0
0
[0240] Results: Table 11 shows that following autoclaving 100% of
Sm-DTPA, 100% La-DTPA, and 100% Eu-DTPA was eluted from each of
their respective CM-Sephadex columns, as is expected for a
negatively charged chelate of the three respective lanthanides. In
contrast 100% of unchelated Sm.sup.+3, La.sup.+3, and Eu.sup.+3 is
retained on the column as expected for a positive ion (Examples 9,
10, and 11). Thus no free Sm.sup.+3, La.sup.+3, or Eu.sup.+3 is
generated during autoclaving. These results demonstrate that the
DTPA chelates of Sm.sup.+3, La.sup.+3, and Eu.sup.+3 are stable to
autoclaving. The DTPA chelate of samarium, lanthanum and europium
and the DTPA chelate of gadolinium are all stable to the process of
autoclaving. As autoclaving is a method of first choice for
providing sterility, the stability of those chelates to autoclaving
enables a rapid, large scale and economical method for
sterilization.
Example 22
Stability of Sm-DTPA, La-DTPA, and Eu-DTPA in Rat Serum
[0241] To 0.45 ml of rat serum was added 50 .mu.l of 1 mM Sm-DTPA,
La-DTPA or Eu-DTPA. To 0.45 ml of rat serum was added 50 .mu.l of 1
mM Sm, La or Eu chloride. The six respective solutions sat at room
temperature for 24 hours. Samples from all six solutions were
assayed as described in Examples 17, 18, and 19, except that 0.2 ml
of sample was applied to column and samples were not diluted.
Fractions were collected as indicated in Table 12. All fractions
were dried at 70.degree. C. for 76 hours, and 25 .mu.l of arsenic
internal standard was added. Samples were activated by exposure to
a neutron flux in a 2 megawatt reactor for 15 minutes. After three
days each sample was counted for 3 minutes.
[0242] Results: Table 12 shows that 100% of the DTPA chelates of
Sm, La, and Eu elute from CM Sephadex columns while approximately
50% of their respective salts are bound to the column. The portion
of unchelated salts eluting from the column was a result of the
free metal ions binding to serum components. Based on the minimum
number of dpms detectable, one can conclude that less than 2% of
the chelated samples was dissociated from DTPA. We conclude that
the DTPA chelates of Sm, La, and Eu are stable in rat seum.
TABLE-US-00013 TABLE 12 Stability of Sm-DTPA, La-DTPA, and Eu-DTPA
in rat serum Fraction # Sample description dpm % of total
Samarium-DTPA STABILITY IN RAT SERUM 1 Apply 0.2 ml of Sm-DTPA from
sample 287916 96 incubated in rat serum, allow sample to drain into
column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 12133 4 3 Column and contents 0 0 Samarium
chloride STABILITY IN RAT SERUM 1 Apply 0.2 ml of SmCl.sub.3 from
sample 104992 48 incubated in rat serum, allow sample to drain into
column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 5702 3 3 Column and contents 108299 49
Lanthanum-DTPA STABILITY IN RAT SERUM 1 Apply 0.2 ml of La-DTPA
from sample 82912 93 incubated in rat serum, allow sample to drain
into column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of
0.01M Tris buffer pH 7.5 6167 7 3 Column and contents 0 0 Lanthanum
chloride STABILITY IN RAT SERUM 1 Apply 0.2 ml of LaCl.sub.3 from
sample 51651 49 incubated in rat serum, allow sample to drain into
column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 6586 6 3 Column and contents 46450 44
Europium-DTPA STABILITY IN RAT SERUM 1 Apply 0.2 ml of Eu-DTPA from
sample 4763 91 incubated in rat serum, allow sample to drain into
column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 499 9 3 Column and contents 0 0 Europium
chloride STABILITY IN RAT SERUM 1 Apply 0.2 ml of EuCll.sub.3 from
sample 2378 42 incubated in rat serum, allow sample to drain into
column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M
Tris buffer pH 7.5 291 5 3 Column and contents 2940 52
Example 23
Effect of Dilution on the Stability of Sm-DTPA
[0243] Sm-DTPA (1 mM) was prepared as described in Example 9. The
solution was further diluted with 0.01 MTris buffer pH 7.5 1:10,
1:100, 1:1000, and 1:10000 and allowed to stand at room temperature
for 24 hours. The four samples were then assayed for stability of
the Sm-DTPA complex as described in Example 17. All samples were
found to be stable, as shown in Table 13. Thus Sm-DTPA forms a
stable complex within the concentration limits of 1 mM to 0.1
.mu.M. TABLE-US-00014 TABLE 13 Effect of dilution on the stability
of Sm-DTPA Fraction % of # Sample description Dpm total
Samarium-DTPA, 1 mM 1 3 ml of 0.01M Tris buffer pH 7.5 0 0 2 1 ml
of Sm-DTPA from Example 9 1482087 97 diluted 1:10 followed by 3 ml
of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5
19089 1 4 Column and contents 24257 2 Samarium-DTPA, 100 uM 1 3 ml
of 0.01M Tris buffer pH 7.5 0 0 2 1 ml of Sm-DTPA (100 uM) 162208
98 diluted 1:10 followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml
of 0.01M Tris buffer pH 7.5 1308 <1 4 Column and contents 2121 2
Samarium-DTPA, 10 .mu.M 1 3 ml of 0.01M Tris buffer pH 7.5 0 0 2 1
ml of diluted Sm-DTPA (10 .mu.M) 15685 100 diluted 1:10 followed by
3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5
19 <1 4 Column and contents 0 0 Samarium-DTPA, 1 .mu.M 1 3 ml of
0.01M Tris buffer pH 7.5 0 0 2 1 ml of diluted SmCl.sub.3 plus DTPA
(1 .mu.M) 1386 96 diluted 1:10 followed by 3 ml of 0.01M Tris
buffer pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 29 2 4 Column and
contents 21 2 Samarium-DTPA, 0.1 .mu.M 1 3 ml of 0.01M Tris buffer
pH 7.5 0 0 2 1 ml of diluted Sm-DTPA (0.1 .mu.M) 192 99 diluted
1:10 followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M
Tris buffer pH 7.5 1 1 4 Column and contents 0 0
[0244] Results: Table 13 shows that 100% of the DTPA chelate of Sm
elutes from CM Sephadex columns within a concentration range of 0.1
.mu.M to 1 mM, indicating that the DTPA chelate of Sm is stable
within this concentration range.
Example 24
Assay of Gd-DOTA
[0245] Preparation of carboxymethyl sephadex column. To a 10 ml
plastic pipet cut off at the 3 ml mark and plugged with glass wool
at the bottom, add enough slurry to form a 2 ml volume of the CM
sephadex. Wash the packed resin with 6 ml of 1 M Tris buffer pH
7.5, and 6 ml of 0.01M Tris buffer pH 7.5. Dilute sample
(Gadolinium-DOTA from Example 12) 1:10 with distilled water (0.2 ml
to 2 ml). Apply fractions as follows. Fraction 1. One ml of sample
A and allow to drain into column. Apply 3 ml of 0.01 M Tris buffer
pH 7.5 and allow to drain into column. Fraction 2. Three ml of
0.01M Tris buffer pH 7.5 and allow to drain into column. Collect
the eluant of fractions 1 and 2. Dry all fractions at 70.degree. C.
for 76 hours, dissolve in 1 ml of 1 mM HCl and assay by atomic
absorption for Gadolinium. TABLE-US-00015 TABLE 14 Assay of Gd-DOTA
Gadolinium-DOTA from Example 12 Fraction # Sample description umol
Gd % of total 1 1 ml of diluted GdCl.sub.3 plus DOTA 0.1 100 from
Example 12 diluted 1:10 followed by 3 ml of 0.01M Tris buffer pH
7.5 2 3 ml of 0.01M Tris buffer pH 7.5 0 0
[0246] Results: Table 14 shows that 100% of Gd-DOTA is eluted from
CM-Sephadex column as expected for a negatively charged molecule.
In contrast 100% of unchelated Gd.sup.+3 is retained on the column
as expected for a positive ion (see Example 16). These results
demonstrate that the DOTA chelate of Gd.sup.+3 forms within 5
minutes, and that this method can be used to ascertain the
formation of metal DOTA chelates.
Example 25
Assay of Sm-DOTA, La-DOTA, and Eu-DOTA
[0247] Preparation of carboxymethyl sephadex column. To a 10 ml
plastic pipet cut off at the 3 ml mark and plugged with glass wool
at the bottom, enough slurry was added to form a 2 ml volume of the
CM sephadex. The packed resin was washed with 6 ml of 1 M Tris
buffer pH 7.5, and 6 ml of 0.01M Tris buffer pH 7.5. Samples from
Examples 13, 14, and 15 were diluted 1:10 with distilled water (0.2
ml to 2 ml). Fractions were applied as follows. Fraction 1. One ml
of sample (Sm-DOTA, La-DOTA, and Eu-DOTA) to individual CM-sephadex
columns and allow to drain into column. Apply 3 ml of 0.01 M Tris
buffer pH 7.5 and allow to drain into column. Fraction 2. Three ml
of 0.01M Tris buffer pH 7.5 and allow to drain into column. Collect
the eluant of Fractions 1 and 2. Fraction 3. Column and contents.
Fractions were dried at 70.degree. C. for 76 hours and 25 .mu.l of
arsenic internal standard was added. Samples were activated by
exposure to a neutron flux in a 2 megawatt reactor for 15 minutes.
After three days each sample was counted for 3 minutes.
TABLE-US-00016 TABLE 15 Assay of Sm-DOTA, La-DOTA, and Eu-DOTA
Fraction % of # Sample description dpm total Samarium chloride and
DOTA from Example 13 1 1 ml of diluted Sm-DOTA from Example 13
1429326 98 diluted 1:10 followed by 3 ml of 0.01M Tris buffer pH
7.5 2 3 ml of 0.01M Tris buffer pH 7.5 28850 2 3 Column and
contents 0 0 Lanthanum-DOTA from Example 14 1 1 ml of diluted
Sm-DOTA from Example 14 410040 97 diluted 1:10 followed by 3 ml of
0.01M Tris buffer pH 7.5 2 3 ml of 0.01M Tris buffer pH 7.5 11681 3
3 Column and contents 0 0 Europium-DOTA from Example 15 1 1 ml of
diluted Sm-DOTA from Example 15 391454 100 diluted 1:10 followed by
3 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M Tris buffer pH 7.5
132 <1 3 Column and contents 0 0
[0248] Results: Table 15 shows that 100% of Sm-DOTA, La-DOTA, or
Eu-DOTA is eluted from CM-Sephadex columns A, B, and C,
respectively, as expected for a negatively charged molecule. In
contrast, 100% of unchelated Sm.sup.+3, La.sup.+3, and Eu.sup.+3 is
retained on their corresponding columns (cf Examples 11, 12, and
13) as expected for a positive ion. These results demonstrate that
the DOTA chelates of Sm.sup.+3, La.sup.+3, and Eu.sup.+3 forms
within 5 minutes, and that this method can be used to ascertain the
formation of metal DOTA chelates. The DOTA chelate of samarium,
lanthanum, and europium and the DOTA chelate of gadolinium have
identical chromatographic behavior.
Example 26
Stability of Gd-DOTA
[0249] Gadolinium-DOTA is stable to autoclaving as demonstrated by
properties of the pharmaceutical product known as DOTAREM.RTM..
Example 27
Stability of Sm-DOTA, La-DOTA, and Eu-DOTA to Autoclaving
[0250] Five ml of each of Sm-DOTA, La-DOTA, and Eu-DOTA prepared in
Examples 13, 14, and 15 were placed in 10 ml glass bottles capped
with a grey butyl rubber cap and crimped. Samples were autoclaved
for 30 minutes at 121.degree. C. Samples were allowed to cool to
room temperature and were assayed as described in Examples 25.
TABLE-US-00017 TABLE 16 Stability of Sm-DOTA, La-DOTA, and Eu-DOTA
to autoclaving Fraction # Sample description dpm % of total
Samarium-DOTA AUTOCLAVED 1 5 ml of Sm-DOTA Example 13 was 1439622
98 autoclaved, 0.1 ml was diluted 1:10and applied to the CM-
Sephadex column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml
of 0.01M Tris buffer pH 7.5 27521 2 3 Column and contents 0 0
Lanthanum-DOTA AUTOCLAVED 1 5 ml of La-DOTA from Example 14 400045
100 was autoclaved, 0.1 ml was diluted 1:10 and applied to a
CM-Sephadex column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3
ml of 0.01M Tris buffer pH 7.5 11 <1 3 Column and contents 0 0
Europium-DOTA AUTOCLAVED 1 5 ml of Eu-DOTA from Example 15 366651
100 was autoclaved, 0.1 ml was diluted 1:10 and applied to a
CM-Sephadex column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3
ml of 0.01M Tris buffer pH 7.5 1226 <1 3 Column and contents 0
0
[0251] Results: Table 16 shows that following autoclaving, 100% of
Sm-DOTA leads to an unstable product producing a mixture of Sm-DOTA
and unchelated Sm.sup.+3. However, 100% of La-DOTA, and Eu-DOTA is
eluted from their respective CM-Sephadex columns as expected for a
negatively charged molecule. In contrast 100% of unchelated
Sm.sup.+3, La.sup.+3, and Eu.sup.+3 is retained on their
corresponding columns (cf Examples 11, 12, and 13) as expected for
a positive ion. These results demonstrate that the DOTA chelate of
La.sup.+3, and Eu.sup.+3 are stable to autoclaving. The DOTA
chelates of each of lanthanum, europium, and gadolinium are stable
to autoclaving.
Example 28
Formation and assay of chelates using enriched stable isotope
metals
[0252] Chelates of DTPA and DOTA are formed as described in
Examples 9-11 (for DTPA chelates) and 13-15 (for DOTA chelates),
except that enriched isotope preparations of the respective
chloride salts of each element are used. Chelate formation is
assayed as described in Examples 17-19 for (DTPA chelates) and 25
(for DOTA chelates). Results obtained with natural abundance
isotopes and enriched isotopes are identical within experimental
error. Table 17 illustrates the gain in sensitivity obtained using
enriched stable isotopes over natural abundance isotopes.
TABLE-US-00018 TABLE 17 Comparison of potency of natural abundance
and enriched stable isotope preparations in neutron activation
analysis. Enriched isotopes preparations were obtained from the
Department of Energy. Abundance Fold increase Element Isotope
Natural Enriched in potency Lanthanum La-139 99.1 99.99 1.01
Samarium Sm-149 13.8 97.68 7.08 Sm-152 26.7 99.44 3.72 Europium
Eu-151 47.8 96.81 2.03 Eu-153 53.2 98.79 1.86
Example 29
Kinetics of Blood Depletion and Urine Accumulation of Sm-DTPA in
the Rat
[0253] One half ml of Sm-DTPA (0.01 mg/kg), dissolved in saline (pH
7), is injected into the tail vein of three rats. Samples of blood
are obtained at 10, 30 and 60 minutes following injection and
analyzed for Sm-DTPA by neutron activation. The percent of starting
amount of the Sm-DTPA at each time interval is presented in Table
18 (last column on right). Similarly, the accumulation of Sm-DTPA
in the rat urine at two times is shown in the last column of Table
18. Results: Table 18 show that the elimination of Sm-DTPA from rat
blood and its accumulation in rat urine is independent of the
presence of other chelated metals when present in low quantities
(compare columns 4 and 5).
Example 30
Kinetics of Blood Depletion and Urine Accumulation of Tc-DTPA,
Gd-DTPA and Sm-DTPA in the Rat
[0254] One half ml of Technetium-99m-DTPA (1 millicurie), Gd-DTPA
(0.05 mg/kg), and Sm-DTPA (0.01 mg/kg) are each dissolved in saline
(pH 7), and are injected simultaneously into the tail vein of three
rats. Samples of blood are obtained at 10, 30 and 60 minutes
following injection and analyzed for .sup.99mTc-DTPA (gamma
counting), Gd-DTPA (T1 relaxation) and Sm-DTPA (neutron
activation). The percent of starting amounts of each of the three
compounds at each time interval presented in Table 18 shows that
each of these compounds exits the rats blood at identical rates
within experimental error. The accumulation of the three compounds
in the rat urine at two times also shows an identical pattern among
the three compounds. Table 18 shows that Sm-DTPA exhibits identical
biological properties with Gd-DTPA and .sup.99mTc-DTPA in the rat
demonstrating its equivalence to two previously accepted compounds
used for measuring glomerular filtration rate (GFR). TABLE-US-00019
TABLE 18 Kinetics of blood depletion and urine accumulation of
Tc-DTPA, Gd-DTPA and Sm-DTPA in the rat. Values shown in bold are
obtained when .sup.99mTc-DTPA, Gd-DTPA and Sm-DTPA are injected
simultaneously (Example 30). The values shown on the column 5 is
obtained using only Sm-DTPA (Example 29). Values represent the
average of three animals. Percent of initial injection administered
Time after simultaneously administered alone injection, min
.sup.99mTc-DTPA Gd-DTPA Sm-DTPA Sm-DTPA Blood 10 85 83 88 86 30 63
65 60 61 60 30 35 33 28 Urine 30 25 22 26 24 180 92 94 90 91
Example 31
Kinetics of Blood Depletion and Urine Accumulation of Sm-DTPA,
La-DTPA and Eu-DTPA in the Rat upon Simultaneous Administration.
Independent and Identical Excretion of Stable Isotope Labeled
Chelates Sm-DTPA, La-DTPA, and Eu-DTPA
[0255] One half ml of Sm-DTPA, La-DTPA and Eu-DTPA (each 0.01
mg/kg), dissolved in saline (pH 7) are injected simultaneously into
the tail vein of three rats. Samples of blood are obtained at 10,
30 and 60 minutes following injection and analyzed for each element
by neutron activation. The percent of starting amounts of each of
the three compounds at each time interval, presented in Table 19,
shows that each of these compounds exits the rat's blood at
identical rates, within experimental error. The accumulation of the
three compounds in the rat urine at two times also shows an
identical pattern among the three compounds. Table 19 shows that
Sm-DTPA, La-DTPA and Eu-DTPA when administered simultaneously are
eliminated independently of the other two chelates. TABLE-US-00020
TABLE 19 Values shown in bold are obtained when Sm-DTPA, La-DTPA
and Eu-DTPA are injected simultaneously (Example 31). The values
shown on the right column is obtained using only Sm-DTPA (Example
29). Values represent the average of three animals. Percent of
initial injection Time after simultaneously administered
administered alone injection, min Sm-DTPA La-DTPA Eu-DTPA Sm-DTPA
Blood 10 83 85 87 86 30 61 63 62 61 60 34 33 33 28 Urine 30 22 23
21 24 180 90 92 96 91
Example 32
Kinetics of Blood Depletion and Urine Accumulation of Sm-DTPA,
La-DTPA and Eu-DTPA in Rat Following Sequential Administration of
Each Chelate: Independent Excretion of Sequential Administrations
of Stable Isotope Labeled Chelates Sm-DTPA, La-DTPA, and
Eu-DTPA
[0256] Samples of Sm-DTPA, La-DTPA and Eu-DTPA (0.5 ml; 0.01
mg/kg), each dissolved in saline (pH 7), are injected sequentially
at 0, 20, and 40 minutes into the tail vein of three rats. Samples
of blood are obtained at 10, 30 and 60 min following each injection
and analyzed for each element by neutron activation. The percent of
starting amounts of each of the three compounds at each time
interval presented in Table 20 shows that each compound exits the
rat's blood at identical rates within experimental error. The
accumulation of the three compounds in rat urine at two times shows
an identical pattern among the three compounds. Table 20 shows that
Sm-DTPA, La-DTPA and Eu-DTPA administered sequentially are each
eliminated independently of the other chelates, and that each
chelate can be measured in the presence of the other chelates
without interference. TABLE-US-00021 TABLE 20 Values shown in bold
are obtained when Sm-DTPA, La-DTPA and Eu-DTPA are injected
sequentially (Example 32). The values shown on the right column are
obtained using only Sm-DTPA (Example 32). Values represent the
average of three animals. Percent of initial injection Time after
sequentially administered administered alone injection, min Sm-DTPA
La-DTPA Eu-DTPA Sm-DTPA Blood 10 81 82 87 86 30 59 62 64 61 60 29
32 34 28 Urine 30 20 25 26 24 180 89 95 97 91
Example 33
[0257] Kinetics of Blood Depletion of Gd-DTPA in the Rat Following
Three Sequential Administrations of the Chelate. Lack of
Independence of Sequential Administrations of Gd-DTPA
[0258] In this theoretical example, three 0.5 ml samples of Gd-DTPA
(0.05 mg/kg) each dissolved in saline (pH 7) are injected
sequentially at 0, 20, and 40 minutes into the tail vein of a rat.
Samples of blood are obtained at 10, 30 and 60 minutes following
each injection and analyzed for Gd by T1 relaxation. The percent of
starting amount of the first injection of Gd at each time interval
presented in Table 21 shows that Gd exits the rat's blood in a
complicated pattern that does not allow the calculation of its rate
of elimination. This example highlights one advantage of using
neutron activation over T1 relaxivity to measure pharmacological
rates of elimination when using sequential injections (compare
Examples 32 and 33). TABLE-US-00022 TABLE 21 Values represent time
of injection and percent of initial value of Gd following the first
injection, the second injection, and the third injection. The
cumulative total value of Gd is calculated based upon the first
injection. Values represent the average of three animals. Time
after Percent of initial injection injection, of First Second Third
Cumulative sample min injection injection injection total 1.sup.st
2.sup.nd 3rd Gd-DTPA Gd-DTPA Gd-DTPA Gd-DTPA 0 100 100 10 81 81 20
0 73 100 173 30 10 59 81 140 40 20 0 47 73 100 220 50 30 10 35 59
81 175 60 40 20 29 47 73 149 70 50 30 26 35 59 120 80 60 40 22 26
47 95 90 70 50 100 80 60 18 22 35 75
Example 34
Comparison of Sensitivity of Gd as Measured by NMR Spectroscopy,
with Sm as Measured by Neutron Activation
[0259] Standards of Gd-DTPA were prepared in phosphate buffered
saline (pH 7.4) to the concentrations indicated in Table 22. One ml
samples of the standards at each concentration were inserted into
the bore of a Brucker PC120 minispectrophotometer, and the T1
relaxation was determined according to the manufacturers
instructions. A plot of pre-determined Gd-DTPA concentration as a
function of experimentally measured mass shows that a strong linear
relationship was obtained (Table 22). A sensitivity (limit of
detection) of between 1 and 10 .mu.M Gd was determined.
[0260] To illustrate the linear range of detection of neutron
activation, the following sensitivity study was undertaken using
two stable-labels: samarium and lanthanum. Atomic absorption
standard solutions of each element were purchased (Sigma, St.
Louis, Mo.). From these standard solutions, test samples were
produced which contained 0.02 .mu.g to 50 .mu.g of each element.
Each sample was placed in a vial containing 0.1 g of bovine liver
tissue, 1 ml human blood, or 5 ml human urine. A metallic monitor
was added to each vial to account for neutron flux density
variations during activation analysis. Samples were dried at
70.degree. C. to remove water. All vials were irradiated for
10-minutes at a power level of one megawatt, which generated an
average neutron flux density of 2.times.10.sup.7 m.sup.-2 s.sup.-1.
Activated vials were stored for 24-hours to allow short-lived
activation productions to decay. Spectrographic analysis was then
performed to measure the concentration of the resultant radioactive
nuclei in each vial.
[0261] The results show a strong linear relationship when
pre-determined samarium and lanthanum masses were plotted as a
function of experimentally measured masses (Table 23). Neutron
activation analysis accurately assessed trace quantities of both
isotopes to levels as low as 0.02 .mu.g (0.1 nmol) with a high
degree of precision. The corresponding detectable concentrations of
stable isotope in liver, blood and urine were 1 .mu.M, 0.1 .mu.M,
and 0.021 .mu.M, respectively. Additional sensitivity may be
obtained by use of increased irradiation time and use of higher
neutron flux field.
[0262] Therefore, this comparative study shows that stable isotope
labeling combined with neutron activation can measure small
concentrations of stable labels to levels as low as 20 nM, which is
a factor of 50 to 500 fold more sensitive then NMR detection of
Gd-DTPA. The results with neutron activation also demonstrate that
measurement results are obtained independent of the presence of
different type of biological tissue. TABLE-US-00023 TABLE 22
Concentrations of Gd-DTPA standards. Detection of Detection of
Sm-DTPA Gd-DTPA by NMR by neutron Detection of in PBS activation
La-DTPA by Concen- Concen- neutron activation tration tration
Concentration (.mu.M) T1 1/T1 (.mu.M) Dpm (.mu.M) dpm 0 3.810
262.502 0 0 0 0 1 3.819 261.835 0.01 123 0.01 52 10 3.314 301.714
0.1 1398 0.1 537 25 2.483 402.739 1 10987 1 5143 50 2.053 487.211
10 123584 10 52879
[0263] TABLE-US-00024 TABLE 23 Linear regression analysis of data
from Table 23. Samarium y = 0.02 + 1.00x r = 1.0 Lanthanum y = 0.03
+ 0.92x r = 0.98 Gadolinium Y = 4.69x + 262.53 r = 0.99
Example 35
Effect of Matrix on the Determination of Sm-DTPA by Neutron
Activation
[0264] One .mu.g of Sm (as Sm-DTPA) was pipetted into sample tubes
prelabeled with monitor. The sample tubes contained either 1 g of
beef liver, 1 ml of human blood or 1 ml of human urine. All samples
were dried at 70.degree. C. for 76 hours, and 25 .mu.l of arsenic
internal standard was added to each sample. Samples were activated
by exposure to a neutron flux in a 1 megawatt reactor for 15
minutes. After three days samples, were counted for 3 minutes. The
results of the three samples are shown in Table 24, and indicate
that neutron activation analysis of stable isotopes is independent
of the matrix. TABLE-US-00025 TABLE 24 Effect of matrix on the
determination of Sm-DTPA by neutron activation Sample Sm Dpm 1 g
liver 1 .mu.g 712353 1 ml blood 1 .mu.g 705228 1 ml urine 1 .mu.g
722241
Example 36
The Use of Iohexol, a Stable Isotope Labeled Iodinated Compound,
and Neutron Activation to Measure GFR in a Rabbit
[0265] One New Zealand White male rabbit (m=2 kg) was sedated with
intramuscular ketamine (35 mg/kg) and xylazine (5 mg/kg). Both the
right and left ear veins were catheterized. One line was used to
inject Iohexol (Omnipaque.RTM., Nycomed, Inc., Princeton, N.J.).
The injected dose (ID) was 90 mg of iodine. After the injection,
the second line was used to collect blood samples at the following
time points--5, 10, 15, 20, 30, 45, 60, 96, 120, 180 minutes. For
each blood sample, 100 .mu.l of serum was placed in a clean sample
vial. A metallic monitor was than added to each vial to account for
potential neutron flux density variations during neutron activation
analysis. Neutron activation was performed in a 2 megawatt reactor
for 1 min and samples were counted within 30 minutes following
activation. Counts were converted into disintegrations per minute
and the measured iodine concentration for each sample was plotted
as a function of time of sample withdrawal. The data was fit to a
two compartment exponential model using the equation: Plasma
concentration=Ae.sup.-(af)+Be.sup.-(bf). The area under the curve
(AUC) from t=0 to t=180 minutes was calculated from the fit. The
GFR (ml/kg/min) was than calculated as follows: GFR=(ID/AUC)/m,
where ID=initial dose of iohexol, AUC=(A/a+B/b), and m=minutes.
[0266] Iohexol is found to be removed from the blood as a smooth
function of time (Table 25). The calculated parameters used to fit
the data were for a two compartment model. The measured GFR value
was 4.8, which is comparable to reported values for normal
rabbits.(57-59) TABLE-US-00026 TABLE 25 Clearance of iohexol from
rabbit blood as a function of time. Clearance of iohexol is
expressed as dpm/.mu.l of blood mg of iohexol/ml of blood. The data
was fit to the curve (Plasma concentration = A e.sup.-(at) + B
e.sup.-(bt)) and the parameters A, a, B and b were determined to be
0.0755, 0.0620, 0.0726, and 0.0089, respectively. A GFR value of
4.80 was determined using the equation above. Iohexal Number Time
dpm/ul mg/ml 1 180 605.5 0.01458 2 120 982.0 0.02365 3 96 1317.8
0.03174 4 60 2032.3 0.04894 5 45 1952.3 0.04702 6 30 2810.5 0.06769
7 20 3689.4 0.08885 8 15 3595.7 0.08660 9 10 4541.7 0.10938 10 5
5166.1 0.12442
Example 37
Result of a Hypothetical Study in Humans Comparing GFR Results
Obtained using Sm-DTPA (Determined by Neutron Activation) with Two
Other Methods (99 mTc-DTPA and Gd-DTPA)
Preparatory Procedures
[0267] Thirty-five patients afflicted with renal dysfunction are
evaluated at the National Institutes of Health (N.I.H.) under an
Institutional Review Board-Approved protocol. The Following
procedure is followed for all patients in the study. The evening
before the study, the patients are given a low salt, low protein
diet. On the morning of the study, intravenous (i.v.) hydration is
started through an i.v. line placed in the arm of each patient
until an adequate urinary output was established. An initial
loading dose is given of oral fluid supplement by 5% wt dextrose in
water intravenous fluid to equal approximately 20 ml/kg of body
weight. The hydration is continued by the i.v. administration of 5%
wt dextrose in water (Mcgaw-Kendall Co., Irvine, Calif.)
supplemented by oral hydration for approximately 3-4 hours at
300-400 ml/hour. A separate intravenous line for blood drawing is
inserted in the arm of the patient and then each patient is
transported to the Nuclear Medicine Department. Intravenous
hydration, supplemented by oral hydration when needed, is continued
for the duration of the study. Preliminary blood (S1, 10 ml) and
urine (U1, 10 ml) samples are obtained prior to applying any
further treatment.
Procedure for Obtaining Blood and Urine Samples
[0268] One millicurie technetium-99m-DTPA, 0.05 mg/kg Gd-DTPA, and
0.01 mg/kg Sm DTPA are simultaneously injected i.v. to each patient
through the hydration line. A second blood sample (S2, 6 ml) is
obtained from each patient after one hour of "equilibrium time."
The equilibrium time is the time in which the compounds reach
equilibrium between intra- and extra-vascular spaces. Samples of
blood and urine are obtained for each of the of the three methods
of measurement (gamma counting, .sup.99mTc; MR relaxation, Gd; and
neutron activation, Sm) at each time point. This set of samples is
collectively referred to as blood and urine samples in the
following description.
[0269] The patient is then encouraged to void. When the patient is
next able to void, usually within 20-25 minutes, a third blood
sample (S3, 6 ml) and a second urine sample (U2, 10 ml) are
obtained for each patient. The volume and time of the interval
since the last voiding event is noted.
[0270] Each patient is then allowed to rest for another "interval,"
after which the patient is again encouraged to void and a fourth
blood sample (S4, 6 ml) and a third urine sample (U3, 10 ml) are
obtained. The volumes and times are recorded, as well.
[0271] This process is repeated once again to obtain fifth blood
and fourth urine samples (S5, 6 ml and U4, 10 ml). The volume:time
ratios or urine rates for the different points obtained are then
compared.
[0272] If the volume:time ratios or urine rates for the three
intervals are comparable, these values are utilized for the
calculations and no more data are obtained for the patient. If,
however, the volume:time ratios or urine rates are found to differ,
further measurements were taken for the patient at additional
intervals until at least three comparable volume:time ratios or
urine rates are obtained. After the procedure is completed, the
intravenous lines are removed and the patient remains free to move
around.
Scintillation Counting of Samples
[0273] The technetium-99m-DTPA labeled samples are counted in a
scintillation counter as is known in the art. A Technetium-DTPA
clearance rate is calculated from these data in accordance with
standard methods known in the art (Licottke, R. R. and Duarte, C.
G., "Lab. Protocol and Meth. Meas. Glomer. Filter Rate and Renal
Plasma Flow", in Renal Function Tests: Clinical Lab. Proc. and
Diag., Duarte C. G., Ed., Little Brown, Boston, pp. 290-63
(1980)).
Relaxation Measurements of Gd
[0274] The Gd-DTPA labeled blood samples are centrifuged to
separate serum and blood products. They are left in a refrigerator
overnight to eliminate the radioactivity present in the blood due
to the presence of .sup.99mTc-DTPA. The half-life of Technetium is
about 6 hours and thus it has almost completely decayed in 24
hours.
[0275] Serum and urine samples are then measured using a Praxis 10
MHz spectrometer with a 90-tau-90 pulse sequence as described by
Farrar et al (Farrar et al, in Pulse and Fourier Transform NMR.
Intro. Theory and Meth., pp. 18-33, Academic Press, N.Y.
(1971)).
[0276] Values are obtained at 30 points for tau and then are
plotted as an exponential curve versus time. The method relies on
an approximate estimation of the actual T1 value of the substance
in the sample being measured. Two T1 values are determined for each
sample.
[0277] The preliminary or pre-injection blood and urine samples are
then "doped" (i.e., given an internal standard) with pre-measured
aliquots of a specified volume of known Gd concentration.
Pre-injection "standards" are thus produced for the urine and serum
samples and their T1s are then measured in the manner described
above. The data for the different samples are then recorded on data
sheets as shown below.
[0278] Data Recording Sheet for Patients in GFR Study
TABLE-US-00027 Data Recording Sheet for Each Patent Name Time
Content Value S1 pre preliminary blood sample SS1 pre blood STD 1 +
Gd-DTPA SS2 pre blood STD 2 + Gd-DTPA S2 post blood start Interval
1 S3 post blood end interval 1 S4 post blood end interval 2 S5 post
blood end interval 3 S6 post blood end interval 4 U1 pre
preliminary urine sample US1 pre urine STD 1 + Gd-DTPA US2 pre
urine STD 2 + Gd-DTPA U2 post urine end interval 1 U3 post urine
end interval 2 U4 post urine end interval 3 U5 post urine end
interval 4 STD: Standard
[0279] Points S6 and U5 are taken only when desired or
necessary.
Neutron Activation of Sm
[0280] Whole blood and urine samples are added to preweighted vials
containing monitor to correct for neutron flux, and are mailed to
the user's facility for neutron activation. The weight of each
sample is determined at the facility. Samples are activated by
exposure to a neutron flux in a 5 megawatt reactor for 15 minutes.
After one day of storage, samples are counted for 3 minutes.
Samarium concentrations in each sample are determined using a
standard curve developed with NIST traceable Sm.
Computation of Results
[0281] Computational methods of the results for .sup.99mTc-DTPA and
Gd-DTPA, and calculation of GFR are as described in U.S. Pat. No.
5,100,646.
[0282] The results (Table 26) show that the method herein, using
stable isotope labeled chelates, Both correlates and agrees with
established methods for determining GFR(R=0.95; .sup.99mTc-DTPA vs
Sm-DTPA. R=0.99; Gd-DTPA vs Sm-DTPA). TABLE-US-00028 TABLE 26
Results of a hypothetical study in humans comparing GFR results
obtained using Sm-DTPA (determined by neutron activation) with two
other methods (.sup.99mTc-DTPA and Gd-DTPA). PATIENT # Tc GFR Gd
GFR Sm GFR 1 57.6 54.5 55.8 2 15.4 15.4 16.3 3 93.4 99.5 103.7 4 86
106 110 5 57.3 54.6 58.6 6 83.2 83.2 82.9 7 139 158 161 8 100 112
108 9 58.9 54.4 52.4 10 65.2 71.6 70.5 11 83.8 77 79.4 12 97.1 97.2
98.0 13 88.4 74.6 82.7 14 83 89 86 15 87 80.3 77.1 16 79.3 76.6
77.8 17 93.2 99 103 18 82.8 93.7 98.4 19 60 65.6 62.4 20 83.2 86.8
88.9 21 54 58.9 60.4 22 74.5 72.3 73 23 101 110 112 24 57.5 59 59
25 100.4 99.2 97 26 82.1 81.3 82 27 65.7 63 64 28 72.4 72.2 72 29
100 109.7 110 30 78.3 84.5 86.3 31 89.6 92.7 91.5 32 77 82.2 79.1
33 51.8 52.3 52.0 34 93.5 102.6 104 35 58.8 58.5 58
[0283] The values with the .sup.99mTc-DTPA clearance test and the
Gd-DTPA clearance test show a good correlation (R=0.96). These data
represent the summation of the GFRs obtained with the Sm-DTPA
clearance method of the invention for 10 patients who received 0.1
mmole/kg wt Sm-DTPA and for 30 patients who received 0.01 mmole/kg
wt.
[0284] The dose of Sm-DTPA administered to the patient does not
significantly alter the accuracy of the results. In view of this
information, establishing the dose to be no greater than the lower
dose of Sm-DTPA is preferred for further applications.
[0285] The invention regarding the use of stable isotope labeled
substances for use in determining GFR now being fully described, it
will be apparent to one of ordinary skill in the art that many
changes and modifications can be made thereto without departing
from the spirit or scope of the invention as set forth herein.
Example 38
Synthesis of Ficoll (MW 70 kDa) carboxymethyl.sub.10.
(Carboxymethyl Ficoll 70)
[0286] Ficoll of molecular weight 70 kDa (0.75 g), and sodium
hydroxide (1.15 g) dissolved in 7.2 ml of deionized water, were
combined with 0.55 g of bromoacetic acid dissolved in 1.425 ml
deionized water. The solution was stirred for 2 hours at 25.degree.
C., neutralized to pH 7 with 6 N hydrochloric acid, and dialyzed
against Spectropor 2 (MWCO 12,000) membrane with deionized water.
The retained material was lyophilized. The conjugate contained 10
mmoles of carboxymethyl group per gram of product as determined by
titration with sodium hydroxide to an endpoint with
phenolphthalein.
Example 39
Synthesis of Ficoll (MW 400) carboxymethyl.sub.10. (Carboxymethyl
Ficoll 400)
[0287] Ficoll of molecular weight 400 kDa (0.75 g), and sodium
hydroxide (1.15 g) were dissolved in 7.2 ml of deionized water, and
were combined with 0.55 g of bromoacetic acid dissolved in 1.425 ml
deionized water. The solution was stirred for 2 hours at 25.degree.
C., neutralized to pH 7 with 6 N hydrochloric acid, and dialyzed
against Spectropor 2 (MWCO 12,000) membrane with deionized water.
The retained material was lyophilized. The conjugate contained 10
mmoles of carboxymethyl group per gram of product as determined by
titration with sodium hydroxide to an endpoint with
phenolphthalein.
Example 40
Synthesis of Inulin Carboxymethyl.sub.10
[0288] Inulin of molecular weight 5 kDa (0.75 g), and sodium
hydroxide (1.15 g), are dissolved in 7.2 ml of deionized water is
combined with 0.55 g of bromoacetic acid dissolved in 1.425 ml
deionized water. The solution is stirred for 2 hours at 25.degree.
C., neutralized to pH 7 with 6 N hydrochloric acid and dialyzed
against Spectropor 2 (MWCO 12,000) membrane with deionized water.
The retained material is lyophilized. The conjugate contains 10
mmoles of carboxymethyl group per gram of product as determined by
titration with sodium hydroxide to an endpoint with
phenolphthalein.
Example 41
Synthesis of Ficoll-CM.sub.10-ethylenediamine (MW 70 kDa; Amino
Ficoll 70)
[0289] The carboxyl groups of carboxymethyl ficoll 70 were
converted to amines by reaction with ethylene diamine.
Carboxymethyl ficoll 70 (0.97 g) was dissolved in 15 ml of water.
Ethylene diamine (1.10 ml) and 1-hydroxybenzotriazol (1.25 g) were
added, and the pH was adjusted to 6.5. The reagent
1-(3-dimethylaminopropyl).sub.3-ethylcarbodiimide hydrochloride
(3.4 g) was added to the Ficoll-CM.sub.10 solution. The reaction
was maintained at 20.degree. C. and pH 6.5 for 24 hours. The
reaction was dialyzed against distilled water and lyophilized. The
number of amine functional groups introduced is assayed using the
OPA Fluorescent assay for primary amines of Pierce Chemical Co. The
yield was 8 mmol amine per gram.
Example 42
Synthesis of Ficoll-CM.sub.10-ethylenediamine (MW 400 kDa; Amino
Ficoll 400)
[0290] The carboxyl groups of carboxymethyl ficoll 400 were
converted to amines by reaction with ethylene diamine.
Carboxymethyl ficoll 400 (0.97 g) was dissolved in 15 ml of water.
Ethylene diamine (1.10 ml) and 1-hydroxybenzotriazol (1.25 g) were
added, and the pH was adjusted to 6.5.
1-(3-dimethylaminopropyl)3-ethylcarbodiimide hydrochloride (3.4 g)
was added to the Ficoll-CM.sub.10 solution. The reaction was
maintained at 20.degree. C. and pH 6.5 for 24 hours. The reaction
was dialyzed against distilled water and lyophilized. The number of
amine functional groups introduced is assayed using the OPA
Fluorescent assay for primary amines of Pierce Chemical Co. The
yield was 8 mmol amine per gram.
Example 43
Synthesis of Inulin-CM.sub.10-ethylenediamine (Amino Inulin)
[0291] The carboxyl groups of carboxymethyl inulin are converted to
amines by reaction with ethylene diamine. Carboxymethyl inulin
(0.97 g) is dissolved in 15 ml of water. Ethylene diamine (1.10 ml)
and 1-hydroxybenzotriazol (1.25 g) are added, and the pH was
adjusted to 6.5. The reagent
1-(3-dimethylaminopropyl).sub.3-ethylcarbodiimide hydrochloride
(3.4 g) is added to the Ficoll-CM.sub.10 solution. The reaction is
maintained at 20.degree. C. and pH 6.5 for 24 hours. The reaction
is dialyzed against distilled water and lyophilized. The number of
amine functional groups introduced is assayed using the OPA
Fluorescent assay for primary amines of Pierce Chemical Co.
[0292] A chelating group is then used to complex a desired stable
isotope and this complex is then reacted with the amino moiety of
the amino-polysaccharide. Various bifunctional chelates are used
for lanthanide elements, such as samarium, lanthanum, europium,
terbium, and dysprosium. One such chelate is
(N.sup.1-p-isothiocyanatobenzyl)-diethylenetriamine-N.sup.1,N.sup.2,N.sup-
.3,N.sup.3-tetraacetic acid (DTTA) which has been used as a
chelating agent to introduce probes used in time-resolved
fluoroimmunoassays. For conjugation of DTTA and other similar
bifunctional chelates the isothiocyanate group of the chelate
reacts with primary amines to form a stable thiourea bond. The
reagent is reacted under mild conditions in 0.1M sodium carbonate
buffer, pH 9.0. Examples are presented using
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA), although use of other bifunctional chelates
is contemplated.
Example 44
Labeling of Amino Ficoll 70 with Samarium (Sm-Ficoll 70)
[0293] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH (5.5) for 5 minutes at 25.degree. C. The
solution is then added dropwise to 10 mg (0.14 .mu.mol) of Amino
Ficoll 70 dissolved in 10 ml of 0.1 M carbonate buffer (pH 9). The
reactants are mixed for 60 minutes at 25 C. Succinic acid (100
.mu.mol) is added as a solid, to convert the remaining amino groups
to carboxyl groups. The solution is incubated for an additional 60
minutes. The solution is dialyzed and lyophilized to obtain about
10 mg of solid containing 10 mol of Sm per mol of ficoll. Chemical
Structure ##STR1##
Example 45
Labeling of Amino Ficoll 70 with Lanthanum (La-Ficoll 70)
[0294] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of lanthanum chloride are
incubated in water pH 5 for 5 minutes at 25.degree. C. The solution
is then added dropwise to 10 mg of Amino Ficoll 70 dissolved in 10
ml of 0.1 M carbonate buffer (pH 9). The reactants are mixed for 60
minutes at 25 C. Succinic acid (100 .mu.mol) is added as a solid to
convert the remaining amino groups to carboxyl groups. The solution
is incubated for an additional 60 minutes. The solution is dialyzed
and lyophilized to obtain about 10 mg of solid containing 10 mol of
La per mol of Ficoll.
Example 46
Labeling of Amino Ficoll 400 with Samarium (Sm-Ficoll 400)
[0295] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH 5 for 5 minutes at 25 C. The solution is then
added dropwise to 10 mg of Amino Ficoll 400 dissolved in 10 ml of
0.1 M carbonate buffer (pH 9). The reactants are mixed for 60
minutes at 25 C. Succinic acid (100 .mu.mol) is added as a solid to
convert the remaining amino groups to carboxyl groups. The solution
is incubated for an additional 60 minutes. The solution is dialyzed
and lyophilized to obtain about 10 mg of solid containing 1.7 moles
of Sm per mol of Ficoll.
Example 47
Labeling of Amino Ficoll 400 with Lanthanum (La-Ficoll 400)
[0296] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p SCN-Bz-DOTA) and 4.5 .mu.mol of lanthanum chloride are
incubated in water pH 5 for 30 minutes at 25 C. The solution is
then added dropwise to 10 mg of Amino Ficoll 400 dissolved in 10 ml
of 0.1 M carbonate buffer (pH 9). The reactants are mixed for 60
minutes at 25 C. Succinic acid (100 .mu.mol) is added as a solid to
convert the remaining amino groups to carboxyl groups. The solution
is incubated for an additional 60 minutes. The solution is dialyzed
and lyophilized to obtain about 10 mg of solid containing 1.7 moles
of La per mol of Ficoll.
Example 48
Labeling of Amino Inulin with Samarium (Sm-Inulin)
[0297] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH 5 for 5 minutes at 25 C. The solution is then
added dropwise to 10 mg of amino inulin dissolved in 10 ml of 0.1 M
carbonate buffer (pH 9). The reactants are mixed for 60 minutes at
25 C. Succinic acid (100 .mu.mol) is added as a solid to convert
the remaining amino groups to carboxyl groups. The solution is
incubated for an additional 60 minutes. The solution is dialyzed
and lyophilized to obtain about 10 mg of solid containing three
moles of Sm per mol of inulin.
Example 49
Labeling of Amino Inulin with Lanthanum (La-Inulin)
[0298] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of lanthanum chloride are
incubated in water pH 5 for 30 minutes at 25 C. The solution is
then added dropwise to 10 mg of inulin dissolved in 10 ml of 0.1 M
carbonate buffer (pH 9). The reactants are mixed for 60 minutes at
25 C. Succinic acid (100 .mu.mol) is added as a solid to convert
the remaining amino groups to carboxyl groups. The solution is
incubated for an additional 60 minutes. The solution is dialyzed
and lyophilized to obtain about 10 mg of solid containing three
moles of La per mol of inulin.
Example 50
Labeling of Albumin with Samarium (Sm) Sm-Albumin
[0299] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride were
incubated in water pH 5 for 5 minutes at 25.degree. C. The solution
was then added dropwise to 6 mg of albumin dissolved in 1 ml of 0.1
M carbonate buffer (pH 9). The reactants were mixed for 60 minutes
at 25.degree. C. The solution was dialyzed and lyophilyzed to
obtain about 6 mg of solid containing 10 mol of Sm per mol of
albumin.
Example 51
Labeling of Ferritin with Lutetium (Lu) Lu-Ferritin
[0300] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of lutetium chloride are
incubated in water pH 5 for 5 minutes at 25 C. The solution is then
added dropwise to 10 mg of ferritin dissolved in 1 ml of 0.1 M
carbonate buffer (pH 9). The reactants are mixed for 60 minutes at
25 C. The solution is dialyzed and lyophylyzed to obtain about 10
mg of solid containing 1.7 moles of Lu per mol of ferritin.
Example 52
Other Chelates that can be Used to Introduce Stable Isotopes as
Chelates into Ficoll and Inulin and other Polysaccharides
[0301] Examples of other chelating groups that can be used to
modify amino ficoll, other amino polysaccharides, proteins, and
other amino containing molecules following a similar chemical
strategy indicated in Examples 44-51 include include
N.sup.1-p-isothiocyanatobenzyl)-diethylenetriamine-N.sup.1,N.sup.2,N.sup.-
3,N.sup.3-tetraacetic acid (DTTA),
p-isothiocyanatobenzyl-diethylenetriaminepentaacetic acid
(p-SCN-Bz-DTPA), and diethylenetriaminepentaacetic acid (DTPA). In
addition, amine terminated chelates such as,
1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid
mono(p-aminoanilide),
2-p-aminobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic
acid, and p-aminobenzyl-diethylenetriaminepentaacetic acid can be
coupled to amino polysaccharides using cross linking agents
(Pierce, Rockford, Ill.) and can be coupled to carboxyl containing
polysaccharides using water soluble carbodiimides.
Example 53
Assay of Sm-Ficoll 70
[0302] Preparation of carboxymethyl Sephadex column. To a 10 ml
plastic pipet cut off at the 3 ml mark and plugged with glass wool
at the bottom, add enough slurry to form a 2 ml volume of the CM
Sephadex. Wash the packed resin with 6 ml of 1 M Tris buffer pH
7.5, and 6 ml of 0.01M Tris buffer pH 7.5. Sm-Ficoll 70 is
suspended in 0.01 M Tris buffer pH 7.5 (10 ug/ml). Apply fractions
as follows. Fraction 1. Three ml of 0.01 M Tris buffer pH 7.5 and
allow to drain into column. Fraction 2. One ml of sample Sm-Ficoll
70 and allow to drain into column. Apply 3 ml of 0.01 M Tris buffer
pH 7.5 and allow to drain into column. Fraction 3. Three ml of
0.01M Tris buffer pH 7.5 and allow to drain into column. Collect
the eluant of fractions 1 through 3. Fraction 4. Column and
contents. Dry all fractions at 70.degree. C. for 76 hours and add
25 .mu.l of Arsenic internal standard. Samples are activated by
exposure to a neutron flux in a 1 megawatt reactor for 15 minutes.
After an interval of three days, samples are counted for 3 minutes.
TABLE-US-00029 TABLE 27 Assay of Sm-Ficoll 70 Fraction # Sample
description dpm % of total Samarium Ficoll 70 from Example 44 1 3
ml of 0.01M Tris buffer pH 7.5 0 0 2 1 ml of diluted Sm-Ficoll
1582087 98 70 from Example 43 followed by 3 ml of 0.01M Tris buffer
pH 7.5 3 3 ml of 0.01M Tris buffer pH 7.5 17089 1 4 Column and
contents 0 0 Samarium chloride from Example 9 1 3 ml of 0.01M Tris
buffer pH 7.5 0 0 2 1 ml of SmCl.sub.3 from 0 0 Example 3 diluted
1:10 followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M
Tris buffer pH 7.5 0 0 4 Column and contents 1128598 100
[0303] Results: Table 27 shows that 100% of Sm-Ficoll 70 elutes
from the CM-Sephadex column as expected for a negatively charged
molecule. In contrast, 100% of unchelated Sm.sup.+3 is retained on
the column as expected for a positive ion. These results
demonstrate that Sm-Ficoll 70 forms a stable complex at pH 7.
Example 54
Assay of La-Ficoll 70
[0304] Preparation of carboxymethyl sephadex column. To a 10 ml
plastic pipet cut off at the 3 ml mark and plugged with glass wool
at the bottom, add enough slurry to form a 2 ml volume of the CM
sephadex. Wash the packed resin with 6 ml of 1 M Tris buffer pH
7.5, and 6 ml of 0.01M Tris buffer pH 7.5. La-Ficoll 70 is
suspended in 0.01 M Tris buffer pH 7.5 (10 ug/ml). Apply fractions
as follows. Fraction 1. Three ml of 0.01 M Tris buffer pH 7.5 and
allow to drain into column. Fraction 2. One ml of sample La-Ficoll
70 and allow to drain into column. Apply 3 ml of 0.01 M Tris buffer
pH 7.5 and allow to drain into column. Fraction 3. Three ml of
0.01M Tris buffer pH 7.5 and allow to drain into column. Collect
the eluant of fractions 1 through 3. Fraction 4. Column and
contents. Dry all fractions at 70.degree. C. for 76 hours and add
25 .mu.l of Arsenic internal standard. Samples are activated by
exposure to a neutron flux in a 1 megawatt reactor for 15 minutes.
After three days samples are counted for 3 minutes. TABLE-US-00030
TABLE 28 Assay of La-Ficoll 70 Fraction # Sample description dpm %
of total Lanthanum Ficoll 70 from Example 45 1 3 ml of 0.01M Tris
buffer pH 7.5 0 0 2 1 ml of diluted La-Ficoll 70 1582087 98 from
Example 44 followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of
0.01M Tris buffer pH 7.5 17089 1 4 Column and contents 0 0
Lanthanum chloride from Example 10 1 3 ml of 0.01M Tris buffer pH
7.5 0 0 2 1 ml of LaCl.sub.3 from 0 0 Example 10 diluted 1:10
followed by 3 ml of 0.01M Tris buffer pH 7.5 3 3 ml of 0.01M Tris
buffer pH 7.5 0 0 4 Column and contents 1128598 100
[0305] Results: Table 28 shows that 100% of La-Ficoll 70 elutes
from the CM-Sephadex column as expected for a negatively charged
molecule. In contrast, 100% of unchelated La.sup.+3 is retained on
the column as expected for a positive ion. These results
demonstrate that La-Ficoll 70 forms a stable complex at pH 7.
[0306] Similar results are obtained for Sm-Ficoll 400, La-Ficoll
400, Sm-Inulin, and La-inulin in analogous experiments.
Example 55
Stability of Sm-Ficoll 70 in Rat Serum
[0307] To 0.45 ml of rat serum, add 50 .mu.l of 1 mM Sm-Ficoll 70,
Sm-Ficoll 400, or Sm-Inulin. Incubate at room temperature for 24
hours. To 0.45 ml of rat serum add 50 ul of Sm chloride. Incubate
at room temperature for 24 hours. Samples were assayed as described
in Example 17, except that 0.2 ml of sample was applied to column,
and samples were not diluted. Collect fractions as indicated in
Table 29. Dry fractions at 70 C for 76 hours and add 25 .mu.l of as
internal standard. Samples are activated by exposure to a neutron
flux in a 1 megawatt reactor for 15 minutes. After three days,
samples are counted for 3 minutes. Results: Table 29 shows that
100% of the Sm chelates of Ficoll 70, Ficoll 400 and inulin elute
from CM Sephadex columns while approximately 50% of the respective
samarium salt is bound to the column. The portion of unchelated
salt eluting from the column is a result of the free metal ions
binding to serum components. Since all of the chelates elute from
the CM-column, one concludes that little to no serum binding occurs
for the three test compounds. Based on the minimum number of dpms
detectable on the column, one concludes that less than 2% of the
samarium dissociates from Ficoll 70, Ficoll 400 or Inulin.
TABLE-US-00031 TABLE 29 Fractionation of Sm chelates of Ficoll 70,
Ficoll 400 and Inulin on Cm Sephadex as an indication of serum
binding dpm % of total Samarium-Ficoll 70 in rat serum 1 Apply 0.2
ml of Sm-Ficol 70 incubated 287916 99 in rat serum, allow sample to
drain into column followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3
ml of 0.01M Tris buffer pH 7.5 1213 <1 3 Column and contents 0 0
Samarium-Ficoll 400 in rat serum 1 Apply 0.2 ml of Sm Ficoll 400
incubated 82912 93 in rat serum, allow sample to drain into column
followed by 2 ml of 0.01M Tris buffer pH 7.5 2 3 ml of 0.01M Tris
buffer pH 7.5 6167 7 3 Column and contents 0 Samarium-Inulin in rat
serum 1 Apply 0.2 ml Sm-Inulin incubated in rat 4763 91 serum,
allow sample to drain into column followed by 2 ml of 0.01M Tris
buffer pH 7.5 2 3 ml of 0.01M Tris buffer pH 7.5 499 9 3 Column and
contents 0 0 Samarium chloride in rat serum (data from Example 22)
1 Apply 0.2 ml of SmCl.sub.3 incubated in rat 104992 48 serum,
allow sample to drain into column followed by 2 ml of 0.01M Tris
buffer pH 7.5 2 3 ml of 0.01M Tris buffer pH 7.5 5702 3 3 Column
and contents 108299 49
Example 56
Simultaneous Bioassay of Lu-DTPA, Sm-Ficoll 70 and La-Ficoll 400 in
Healthy Rats
[0308] This example illustrates the application of using multiple
compounds labeled with different stable isotopes to measure
simultaneously different biological activities. In this example,
LU-DTPA is used to measure glomerular filtration rate, while
Sm-Ficoll-70 and La-Ficoll-400 are used to measure degradation of
glomerular size selectivity. As the glomerular structure breaks
down over time, first assay compounds such as Sm-Ficoll-70, of
molecular weight or size just above the cut off limit of normally
functioning glomerulus, will pass into the urine, followed later in
disease progression by larger molecules such as La-Ficoll-400,
which will pass into the urine as a result of further glomerular
deterioration.
[0309] In this example in normal rats with healthy glomerular
filtration, only the Lu-DTPA will pass into the urine. The
Sm-Ficoll-70 however is small enough to equilibrate with the
interstitial space accounting for an initial decrease in blood
concentration. This molecule will then slowly leave the blood but
remain in the animal. Sa-Ficoll-400, because of its higher
molecular weight will remain in the blood and not equilibrate
readily with the interstitial space. It will slowly leave the blood
through opsonization processes.
Biodistribution.
[0310] Rats (300-375 g) used in all studies are male hooded/BBZDR
from BioMedical Research Models (Worcester, Mass.). For each set of
experiments, three rats are anesthetized with Nembutal. The carotid
artery and jugular vein are exposed, and each animal receives via
jugular vein an injection of Lu-DTPA, Sm-Ficoll 70 and La-Ficoll
400 (50 ug/kg). At various times, blood samples are removed from
the tail. Urine samples are collected using a metabolic cage.
Neutron Activation.
[0311] Lutetium, samarium, and lanthanum content in all samples are
each quantitated by the user's facility (for example, BioPAL,
Worcester, Mass.; www.biopal.com). Samples are placed in 2-ml
polypropylene tubes free of trace element contaminants and dried at
70.degree. C. for at least 12 hours. An internal standard of
tungsten is added to each sample, to correct for variations in
neutron flux. Samples are activated for 15 minutes in a neutron
field created by a 2-megawatt nuclear reactor. Short lived
activated products, principally resulting from sodium and chloride,
are allowed to decay for two days, and the remaining radioactivity
from activated samarium or gold is counted using a high resolution
gamma spectrometer.
[0312] The fate of Lu-DTPA, Sm-Ficoll 70 and La-Ficoll 400 after
intravenous injection into rats is examined by obtaining the
biodistribution of the compounds 24 hours after injection.
Biodistribution of the compounds is inferred by the presence of
lutetium, samarium, and lanthanum in tissues after the injection of
Lu-DTPA, Sm-Ficoll 70 and La-Ficoll 400. Lu-DTPA is found only in
the urine, consistent with its low molecular weight and lack of
strong interaction with blood components and cells. Sm-Ficoll 70
and La-Ficoll 400 are present in the liver (.about.10-20% of
injected dose), with most of the initial dose remaining in the
blood after 24 hours, consistent with a long blood-half life. Blood
levels of Sm-Ficoll 70 are lower due to its ability to enter the
interstitial space compared with La-Ficoll 400, which remains
principally in the blood. Trace amounts are found in the spleen,
lung, and muscle. The lack of renal clearance of Sm-Ficoll 70 and
La-Ficoll 400 is consistent with their molecular weights. Blood
clearance and appearance in the urine as a function of time for
Lu-DTPA, Sm-Ficoll 70 and La-Ficoll 400 are presented in Table 30.
These results are consistent with the literature reports for low
molecular weight chelates and high molcular weight polymers.
TABLE-US-00032 TABLE 30 Bioassay of Lu-DTPA, Sm-Ficoll 70 and
La-Ficoll 400 in healthy rats Lu Sm La Lu Sm La % of initial % of
initial Time injection in blood injection in urine 0 100 100 100 0
0 0 15 min 80 30 min 61 22 60 min 34 85 98 2 0 4 hr 2 92 8 hr 96 16
hr 24 hr 0 47 83 100 5 0
Example 57
Synthesis of the Ethylene Diamine Amide of Cholic Acid (EDAC)
[0313] Activation of cholic acid [1]. In a 20 ml vial, 1 g cholic
acid was dissolved in 5 ml dimethylformamide. N-methylmorpholine
(0.286 ml) was added and mixed. Ethylchloroformate (0.3 ml) was
diluted in 2.7 ml dimethylformamide and immediately added to the
cholic acid dropwise with mixing. The mixture was reacted for 30
minutes at room temperature, and formation of a precipitate was
observed.
[0314] Formation of the ethylene diamine amide of cholic acid [2].
Ethylene diamine (0.7 ml) was added to 5 ml dimethylformamide
dropwise with stirring to the activated cholic acid, and allowed to
react for 60 minutes at room temperature. A gummy oil precipitated
on the glass container.
[0315] Purification. The supernatant was added to 50 ml of water,
and a milky suspension was obtained. This was dialyzed against
water to remove low molecular contaminants while retaining the
colloidal product.
[0316] Alternative purification. Add 5 ml of water (pH 8.5) to the
reaction in [2], and extract three times with 10 ml of ethyl
acetate. Back extract the ethyl acetate twice with water (pH 8.5).
Dry the ethyl acetate over anhydrous magnesium sulfate, and
evaporate the ethyl acetate to obtain the product of the yield of
which was 733 mg.
Example 58
Labeling of [12] with Samarium (Sm-Cholic Acid). Labeling a Bile
Acid
[0317] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH (5.5) for 5 minutes at 25.degree. C. The
solution is then added dropwise to 5 .mu.mol of ethylene diamine
amide of cholic acid in the reaction of [2] dissolved in 0.1 M
carbonate buffer pH 9. The reactants are mixed for 60 minutes at 25
C to obtain Sm-cholic acid [3].
[0318] Purification. Add 5 ml of water (pH 8.5) to [3] and extract
three times with 10 ml of ethyl acetate to remove unreacted
ethylene diamine amide of cholic acid in the reaction of [2].
Discard the ethyl acetate, and dry the aqueous phase by
lyophilization to obtain the
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid adduct of ethylene diamine amide of cholic acid.
Example 59
Labeling of Glycine with Samarium (Sm-Glycine). Labeling an Amino
Acid
[0319] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH (5.5) for 5 minutes at 25.degree. C. The
solution is then added dropwise to 7 .mu.mol of glycine dissolved
in 0.1M carbonate buffer (pH 9). The reactants are mixed for 60
minutes at 25 C to obtain Sm-glycine.
[0320] Purification. The product is purified by ultrafiltration
using a 500 molecular weight cutoff membrane to separate unreacted
glycine (MW 75) from the
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid adduct of glycine (MW 937). The retained fraction is dried
by lyophilization to obtain a white powder.
Example 60
Labeling of Folate with Samarium (Sm-Folate). Labeling a
Vitamin.
[0321] Five .mu.mol of
p-amino-benzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic
acid (p-amino-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH (5.5) for 5 minutes at 25.degree. C. The
solution is then added to 7 .mu.mol of folate and 30 mmol of EDAC
(water soluble carbodiimide) dissolved in 0.1 pyridine buffer (pH
5.5). The reactants are mixed for 180 minutes at 25 C to obtain
Sm-folate.
[0322] Purification. The product is purified by ultrafiltration
using a 500 molecular weight cutoff membrane to separate unreacted
EDAC and folate from the
p-amino-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Sm
adduct of folate. The retained fraction is dried by lyophilization
to obtain a white powder.
Example 61
Labeling of Estradiol with Samarium (Lu-estradiol). Labeling a
Steroid.
[0323] Estradiol-17.beta.-hemisuccinate prepared by reaction of
estradiol and succinic anhydride following procedures known in the
art. The hemisuccinate is then activated with ethylchloroformate
and reacted with an excess of
p-amino-benzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic
acid. Unreacted
p-amino-benzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraace-
tic acid is separated from the
estradiol-p-amino-benzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraace-
tic acid adduct by extraction with ethylacetate against pH 2 water.
The purified adduct is charged with a stoichiometric amount of
LuCl.sub.3 to form Lu-estradiol.
Example 62
Labeling of Tobramycin with Samarium (Sm-Tobramicin). Labeling an
Antibiotic
[0324] Five .mu.mol of
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid (p-SCN-Bz-DOTA) and 4.5 .mu.mol of samarium chloride are
incubated in water pH (5.5) for 5 minutes at 25.degree. C. The
solution is then added dropwise to 7 .mu.mol of tobramycin
dissolved in 0.1M carbonate buffer (pH 9). The reactants are mixed
for 60 minutes at 25 C to obtain Sm-tobramycin.
[0325] Purification. The product is purified by ultrafiltration
using a 500 molecular weight cutoff membrane to separate unreacted
tobramycin (MW 467) from the
p-isothiocyanatobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceti-
c acid adduct of tobramycin (MW 1329). The retained fraction is
dried by lyophilization to obtain a white powder.
Example 63
Measurement of Sm-Cholic Acid Clearance from the Blood
Patients and Control Groups
[0326] Sixteen patients are evaluated at the National Institutes of
Health (N.I.H.) under an Institutional Review Broad-Approved
protocol. The following procedure is followed for all patients in
the study.
[0327] Nine patients with clinical diagnosis of Laennec's
cirrhosis, confirmed by liver biopsy, are selected for the study
(Table 1). None of the patients is azotemic or in hepatic coma when
studied, although the majority have ascites and are undergoing
diuretic therapy. The age, sex and liver function tests are listed
in Table 31. The control group, consisting of seven patients
similar in age to the cirrhotic group, are hospitalized patients
having no clinical or laboratory evidence of liver or biliary tract
disease. TABLE-US-00033 TABLE 31 Clinical information and bile acid
data on patients with Laennec's cirrhosis Bilirubin Prothrombin
Direct/ Albumin/ time/patient Sex/ Total Globulin over control
Esophageal Age mg/100 ml g/100 ml Seconds Ascites* varices.perp.
M/56 5.8/9.3 2.3/4.1 20/13 + + F/48 10.2/14.2 2.6/3.8 21/14 ++ +
M/60 1.6/3.0 2.5/4.0 20/13 ++ + M/62 /1.8 3.3/3.6 22/14 ++ + M/42
/1.4 2.4/3.8 19/13 ++ + M/54 /1.0 3.0/4.0 16/13 + M/40 6.4/8.4
2.8/3.1 21/14 ++ M/38 11.4/14.0 3.1/3.3 26/14 ++ + M/60 1.6/
4.0/3.0 22/14 + *+ = physical signs without increased abdominal
girth; ++ = increased abdominal girth; .perp.= by radiology or
esophagoscopy.
Methods
[0328] The dose of each labeled agent is determined by weight.
.sup.14C-Cholic acid (0.14 .mu.Ci/kg) and Sm-cholic acid (0.01
mg/kg) are simultaneously administered to each patient i.v. Serial
plasma specimens are obtained from a vein other than the one
injected at time points 10, 20, 40, and 60-minutes, and then daily,
after injection. The volume of each plasma collection is measured,
than .sup.14C and Sm concentration are determined (scintillation
counting for .sup.14C; neutron activation for Sm).
Scintillation Count of Samples
[0329] Half of the volume of plasma of each sample is used to
determine the .sup.4C-cholic acid concentration. The
.sup.14C-cholic acid samples are counted in a scintillation counter
as is known in the art. The .sup.14C-cholic acid clearance rate is
calculated from these data in accordance with standard methods
known in the art.(14,60)
Neutron Activation Analysis
[0330] The other half of the plasma volume is used to determine
Sm-cholic acid concentration. Plasma samples are placed in vials
containing pre-added monitor to correct for neutron flux
variations, and are mailed to the facility, e.g., BioPAL, Inc. for
analysis. Samples are activated by exposure to a high neutron flux
generated by a two megawatt reactor for 15-minutes. After two days
of decay, samples are counted for 3-minute using a high-resolution
gamma-ray counting system. Samarium concentration in each sample is
determined using a standard curve developed with a reference batch
of samarium of known concentration.
Computation of the Results
[0331] Rates of clearance of injected Sm-cholic acid in a group of
seven normal subjects during the first 60-minutes are compared to
that of nine patients with cirrhosis (FIG. 4). In the normal group,
the mean half time of cholic acid is 30.7.+-.6.2 minutes, whereas
in the cirrhotic group the half time is approximately four times
longer, averaging 120.7.+-.53.9 minutes. The difference is highly
significant. TABLE-US-00034 TABLE 32 Clearance rates in (min) for
labeled cholic acid in Laennec's cirrhotic and normal patients.
Laennec's Cirrhosis Normal Control .sup.14C r.sup.2 Sm r.sup.2
.sup.14C r.sup.2 Sm r.sup.2 1 67.5 0.96 64.7 0.97 1 29.3 0.98 28.5
1.00 2 75.8 0.99 73.0 0.99 2 33.3 0.97 30.9 0.99 3 105.1 0.99 95.8
1.00 3 33.6 0.97 34.6 0.98 4 113.3 0.99 115.8 1.00 4 17.3 0.96 18.2
0.96 5 165.7 0.97 150.9 0.99 5 34.1 0.99 32.7 0.99 6 181.3 0.96
195.0 0.96 6 33.8 0.98 37.4 0.99 7 223.3 0.97 213.7 0.97 7 33.3
0.96 32.6 0.97 8 80.2 0.98 89.6 0.99 9 88.7 0.97 87.6 0.99 Average
122.3* 120.7 h Average 30.7 30.7 s.d. 54.7 53.9 s.d. 6.1 6.2 P = NS
.sup.14C vs. Sm in Laennec's cirrhosis group; P = NS .sup.14C vs.
Sm in control group; *P = 0.0006 Laennec's cirrhosis group vs.
control for .sup.14C-cholic acid; hP = 0.0006 Laennec's cirrhosis
group vs. control for Sm-cholic acid.
[0332] Similar values are obtained using co-injected
.sup.14C-cholic acid. Table 32 lists values obtained for each
patient. In the normal group, mean half-time of cholic acid is
30.7.+-.6.1 minutes, whereas in the cirrhotic group the half-time
is approximately four times longer, averaging 122.3.+-.54.7
minutes. The difference is again highly significant. In both
groups, no significant difference is observed when values obtained
by .sup.14C-cholic acid are compared to values obtained by
Sm-cholic acid. In the normal subjects, plasma activity (.sup.14C
and Sm) is undetectable in all specimens obtained more than 6-hours
after injection. In striking contrast, significant plasma activity
is demonstrable for up to 14 days.
Example 64
Bioassay of Sm-Taurocholic Acid (Sm-TCA) Oral Ingestion
Patient Group
[0333] Twenty consecutive patients with chronic or recurrent
diarrhea of unknown cause are investigated with Sm-TCA and
.sup.75SeHCAT test. Urgent watery diarrhea is the major problem in
all patients. Lactose restricted diet, loperamide or
anticholinergic agents has not relieved their symptoms. Patients
with periods of constipation, dominating abdominal pain or
fragmented mucus stool are excluded. All patients have a long
history of diarrhea without known cause, and a mean age of 13 years
(range 3 months to 30 years). Clinical, endoscopic and radiological
examinations are performed, as well as laboratory tests, to exclude
inflammatory bowel disease, lactose intolerance, celiac disease,
abuse of laxatives or other causes of diarrhea.
Methods
[0334] One capsule of 10 .PHI.Ci .sup.75SeHCAT (Amersham
International) and one capsule of 0.7 mg Sm-TCA (BioPAL, Inc.) are
simultaneously swallowed with water by the patient after an
overnight fast. Stool samples are collected every 24-hours over a
5-day period. The date and time of collection are recorded.
Measurement of .sup.75SeHCAT
[0335] Samples of homogenized 24-hour stool collections are
precisely weighed and combusted in a tube-oven. Radioactivity is
measured using a collimated 2-inch NaI crystal in a selected
standard geometry, as is known in the art. Daily excretion is
expressed as the fraction of the administered dose. Elimination of
bile acids from a pool is found to follow first order kinetics;
turnover is expressed as half-time (days) of elimination of the
administered dose of .sup.75SeHCAT in accordance with standard
methods known in the art.(25)
Neutron Activation Analysis
[0336] Dried stool samples are placed in vials containing monitor
to correct for neutron flux variations and are mailed to a
facility, for example, BioPAL, Inc. for analysis. Samples are
activated by exposure to a high neutron flux generated by a two
megawatt reactor for 15-minutes. Following two days of decay,
samples are counted for 3-minute using a high-resolution gamma-ray
counting system. Samarium concentration in each sample is
determined using a standard curve developed with reference
samarium. The results obtained for Sm-TCA are expressed above as
for .sup.75SeHCAT.
Computation of the Results
[0337] As shown in FIG. 5, daily excretion of each tracer,
expressed as percentage of the administered dose, shows an
excellent correlation with the other tracer (P<0.005, paired
t-test). Both tracers exhibit identical physical behavior with
respect to resorption and excretion phenomena. As shown in FIG. 6,
no significant deviation from the identical function is found
(P>0.05, paired t-test) when the half-times of the bile acid
elimination are compared.
Example 65
Preparation of Arabinogalactan Coated Ferrite Particles
[0338] A general process for the preparation of arabinogalactan
coated ferrite particles follows.(25) An aqueous solution of
trivalent and divalent metal salts is prepared by use of the
following amounts of ferric and ferrous halide salts:
FeCl.sub.3.6H.sub.2O (15.8 g, 58.6 mmol) and FeCl.sub.2.4H.sub.2O
(6.24 g, 31.6 mmol) are combined in 200 ml distilled water and the
resulting solution is filtered through a 0.22 .mu.m filter. Equal
volumes of this metal halide solution and a carbohydrate solution,
prepared by dissolving arabinogalactan (from larch wood, 60 g,
Sigma Chemical Co.) in 120 ml distilled water are then combined at
ambient temperature with stirring. To this mixture is added
dropwise a 30% solution of ammonium hydroxide until the pH of the
mixture reaches about 10, and the mixture is heated to 90.degree.
C. for 15 minutes. The mixture is cooled, and a black colloidal
superparamagnetic iron oxide is obtained. Excess arabinogalactan is
removed by ultrafiltration using a 300 kDa molecular cutoff
membrane. The filtered product, obtained with a yield in iron of
about 90%, is refrigerated until needed.
[0339] Following this procedure a number of new products labeled
with stable isotopes can be made without change to the above
chemical procedure, other than the substitution of one isotope or
one element for either ferric or ferrous chloride. Illustrative of
possible metal atom substitutions are the substances and
proportions presented in Table 33 This list is presented for
purposes of illustration and should not be construed to limit the
possible types of substitutions by stable isotope labeled metals.
TABLE-US-00035 TABLE 33 Possible metal substitutions in the
preparation of ferrites Sample 1 50% of .sup.56Fe.sup.3+ will be
substituted with an equivalent molar amount of .sup.58Fe.sup.3+
Sample 2 10% of .sup.56Fe.sup.2+ will be substituted with an
equivalent molar amount of .sup.57Co.sup.2+ Sample 3 20% of
.sup.56Fe.sup.2+ will be substituted with an equivalent molar
amount of .sup.57Co.sup.2+ Sample 4 10% of .sup.56Fe.sup.3+ will be
substituted with an equivalent molar amount of Sm.sup.3+ Sample 5
20% of .sup.56Fe.sup.3+ will be substituted with an equivalent
molar amount of Sm.sup.3+ Sample 6 10% of .sup.56Fe.sup.3+ will be
substituted with an equivalent molar amount of La.sup.3+ Sample 7
20% of .sup.56Fe.sup.3+ will be substituted with an equivalent
molar amount of La.sup.3+
Example 66
Preparation of Arabinogalactan Coated Non Ferrite Particles
[0340] A general process for the preparation of arabinogalactan
coated non-ferrite particles follows. An aqueous solution of
trivalent or divalent metal salt (M) is prepared by use of the
following amounts of salt: MCl.sub.2 or MCl.sub.3 (58.6 mmol) is
dissolved in 200 ml distilled water and is filtered through a 0.22
.mu.m filter. Equal volumes of this metal halide solution and a
carbohydrate solution, prepared by dissolving arabinogalactan (from
larch wood, 60 g, Sigma Chemical Co.) in 120 ml distilled water are
then combined at ambient temperature with stirring. To this mixture
is added dropwise a 30% solution of ammonium hydroxide, until the
pH of the mixture reaches about 10, and the mixture is heated to
90.degree. C. for 15 minutes. The mixture is cooled, and a
colloidal metal oxide is formed. Excess arabinogalactan is removed
by ultrafiltration using a 300 kDa molecular cutoff membrane. The
filtered product, obtained with a yield in M of about 90%, is
refrigerated until needed. M is chosen so that it contains a stable
isotope suitable for neutron activation. Following this procedure a
number of new products can be made without change in the chemical
procedure other then the substitution of one isotope or one element
for M chloride.
Example 67
Synthesis of Colloidal Gold Coated with Galactose Clusters
[0341] Gold nano-particles of size 10 nm coated with albumin are
purchased from Sigma Chemical Co. The surface coat of albumin is
modified with lactose to produce a lactosylated albumin coated gold
nanoparticle. Galactose terminal sugars are coupled to albumin
using lactose, a reducing disaccharide, by the method of Schwartz
and Gray as follows. [Schwartz, 1977 #132] Sixty-seven milligrams
of albumin coated gold nanoparticles, 100 mg of lactose containing
10 .mu.Ci of .sup.14C-lactose, and 42 mg of sodium cyanoborohydride
are dissolved in 5 ml of 0.2 M potassium phosphate buffer (pH 7),
and incubated at room temperature for about 100 hr. Upon completion
of the reaction excess reagents are removed by diafiltration.
Example 68
Synthesis and Filter Sterilization of Colloidal Gold Coated with
Galactose Clusters (PolyGalactoseGold.TM.)
[0342] Uncoated 10 nm gold particles are purchased form Sigma
Chemical Co. These particles are added to an aqueous solution of
lactosylated albumin (5 mg/ml) incubated for 30 minutes at room
temperature and are ultrafiltered against a 300 kDa molecular
weight cutoff membrane, with five changes of phosphate buffered
saline (pH 7.4) to remove excess lactosylated albumin. The
resulting solution is passed through a 0.2 .mu.m filter, and the
sterile solution is stored at 4.degree. C.
Example 69
Measurement of Receptor Activity Using Colloidal Gold Coated with
Multiple Galactose Moieties (Example 68)
[0343] While effort has been devoted to developing drug delivery
systems utilizing the asialoglycoprotein receptor, there is still a
need for simple, easy to use assays to measure this receptor
activity in vivo. In this example, measurement of the
asialoglycoprotein receptor in normal rats is presented using
stable isotope labeling and neutron activation.
Receptor Interaction and Biodistribution.
[0344] Rats (300-375 g) used in all studies were male hooded/BBZDR
from BioMedical Research Models (Worcester, Mass.). For each set of
experiments three rats were anesthetized with Nembutal. The carotid
artery and jugular vein were exposed and the animal administered
PolyGalactoseGold (50 .mu.g/kg) or albumin coated gold (50
.mu.g/kg) via jugular vein injection. Second set of animals was
injected with 100 mg/kg of asialofetuin followed by
PolyGalactoseGold. At various times blood samples were removed from
the carotid artery.
[0345] After 60 minutes the animals were sacrificed and
approximately one-gram amounts of various tissues were recovered
for quantitation of samarium or gold. Tissues were blotted to
remove blood and clots. No additional processing of tissue such as
perfusion was necessary to perform neutron activation analysis.
Neutron Activation.
[0346] Gold content in all samples was quantitated by a facility
such as BioPAL (Worcester, Mass.; www.biopal.com). Samples were
placed in 2-ml polypropylene tubes free of trace element
contaminants and dried at 70.degree. C. for a minimum of 12 hours.
An internal standard of tungsten, to correct for variations in
neutron flux, was added to each sample. Samples were activated for
15 minutes in a neutron field created by a 2-megawatt nuclear
reactor. Short lived activated products, principally resulting from
sodium and chloride, were allowed to decay for two days and the
remaining radioactivity from activated samarium or gold was counted
using a high resolution gamma spectrometer.
[0347] The fate of PolyGalactoseGold after intravenous injection
into rats and mice was examined by obtaining the biodistribution of
the conjugate 60 minutes after injection. Biodistribution of the
conjugate was inferred by the presence of gold in tissues after the
injection of PolyGalactoseGold. PolyGalactoseGold was found to be
present in the liver (.about.100% of injected dose) but not in the
spleen, adrenals, lung, kidney, heart, marrow, brain, muscle or
urine. When asialofetuin, a ligand for the asialoglycoprotein
receptor of hepatocytes, was coinjected with PolyGalactoseGold,
blood clearance of PolyGalactoseGold was substantially slower (FIG.
3). When albumin coated colloidal gold (see Example 66) was
substituted for PolyGalactoseGold, blood clearance for albumin
coated gold was also substantially slower than that seen with
PolyGalactoseGold, demonstrating the specific role of galactose for
clearing PolyGalactoseGold. These results are consistent with the
literature reports that lactosylated albumin is a ligand of the
asialoglycoprotein receptor, and indicate that the hepatic
clearance of PolyGalactoseGold was mediated by the
asialoglycoprotein receptor. The lack of renal clearance of
PolyGalactoseGold is consistent with its size (20 nm) which
corresponds to a molecule about the size of IgM.
[0348] Using the activation procedure described in the methods, one
nanogram of gold corresponding to about 800 dpm could be easily
distinguished from the background (about 5 dpm).
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* * * * *
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