Technical notes
The mixture was stirred for 1-2 rain, then the pH was adjusted to 7 with 0.5 N NaOH. It was passed through a sterile 0.22 /am Millipore membrane filter into a sterile vial. An appropriate amount of sterile 99Tcm (NaTcO4) in 1-2 ml saline was added to the vial and the mixture was shaken for a few seconds.
International Journal of Applied Radiation and Isotopes, VoL 29, pp. 697-698 Pergamon Press Ltd., 1978. Printed in Great Britain
99Tc'-Glutathione:
697
Labelling
and distribution in ram
Chromatography Paper and thin-layer chromatography was used to determine the labelling efficiency and the amount of free pertechnetate and hydrolyzed-reduced technetium in the preparation. For paper chromatography the descending technique, using Whatman No. 3 mm chromatography paper and saline as a solvent, were used. Thin-layer chromatography was performed on Gelman silica gel ITLC-SG strips. The solvents used were acetone, saline, 85% aq. methanol and n-butanol/acetic acid/water (6/2/2). Paper and ITLC strips were scanned on a chromatogram scanner (Actigraph III, Nuclear Chicago) to determine the radioactivity peaks.
(Received 16 February 1978)
Introduction IN rms study glutathione was labelled with 99Tcm in the hope of imaging the pancreas. Selenium-75-selenomethionine is the only radiodiagnostic agent in currently routine use for pancreas scanning,(t-3) however it has obvious drawbacks from the standpoint of the long physical and biological' " half-times. (4)(TI/2P~---120d, Tl/2b = 144d) and the low pancreas uptake.
Biological distribution studies
Materials and methods
Four rats were injected with 0.5 ml ( ~ 200 gCi) 99Tc~ glutathione through the tail vein. Two of them were sacririced after 30 rain and the other two after 60 min. All the organs and the urinary bladder were removed, weighed and counted on a flat-top scintillation counter (Nuclear Chicago) against a standard prepared from a dilution of the injection solution. The percentage dose taken up by each organ and the per cent of the injected dose/g organ were calculated.
Radiolabelling of glutathione Glutathione (crystalline, reduced form) was supplied by Sigma Chemical Company. 99TC' was obtained from a generator (Radiochemical Centre, Amersham, England). The following procedure was used for labelling: 20rag giutathione was dissolved in 2 ml distilled water while stirring. SnCI2.2H20 solution (1 mg/ml) was added (0.5 ml).
TABLE 1, Paper and thin-layer chromatography data of 99Tcm-glutathione Medium
Solvent
RI
% Radioactivity
0 0.90-0.95
0 100
Paper Whatman No. 3 mm
Saline
ITLC-SG
Acetone
Thin-layer Saline 85% aq. methanol n-butanol/a.a.//-I20 (6/2/2)
0 1.0 0 0-1.0 0 0--1.0 0
100 0 10 90 20 80 50
0--1.0
50
TABLE 2. Organ distribution of 99Tc~-glutathione in rats 30 rain Organ Pancreas Liver Spleen Kidney Stomach Intestine Lung Heart Bladder Pancreas/liver Pancreas/kidney
% Dose 2.8 + 0.9 11.0 + 0.2 2.2 + 0.7 17.0 + 0.5 6.1 + 0 . 4 12.6 + 1.1 11.6 + 1.9 2.8 5- 0.1 16.7+0.3
% Dosc/g
60 min
% Dose
8.2 + 2.3 1.5 + 0.2 1.4 + 0.07 13.1 + 1.7 5.8 + 1.3 2.2 5- 0.6 10.1 + 0.8 17.7 + 1.1 2.4+0.04 5 . 4 + 1.2 0.91 + 0.04 13.2 5- 1.1 6.0 + 0.8 !1.3 5- 3.2 6.8 5- 1.6 2.2 + 0.1 4 1 + 10.1 17.6+ 1.1 5.8 5- 1.9 0.81 5- 0.16
~o Dose/g 4.7 + 0.5 1.7 + 0.6 4.3 + 0.1 10.6 5- 1.9 1.8 + 0 . 9 0.85 + 0.20 5.4 + 0.7 3.7 + 0.2 34.9+23.9 2.9 __+1.3 0.45 + 0.12
698
Technical notes
Scintigraphic studies Two rats were injected with 0.5 ml (500/zCi) 99Tt~-glutathione through the tail vein. They were scanned at 15, 30 and 60rain after injection using a Gamma Camera (Nuclear Chicago) and pinhole colimator.
Results and Discussion The paper and thin-layer chromatography results are summarized in Table 1. When descending paper chromatography was used one broad peak was obtained giving a maximum, at Rf 0.90--0.95. This peak contains 99Tc"glutathione, however it might also contain some free TcO2 ion, since TcO£ has an R I value of 0.75-0.80. Lack of radioactivity at the origin indicates that there is no hydrolyzed-reduced technetium. In thin-layer chromatography when acetone was used as a solvent one peak was obtained at the origin. No activity was observed at Rr 1.0 which indicates the absence of free pertechnetate. The other solvent systems failed to separate the complex from the contaminants. Varying amounts of radioactivity were seen at the origin with the rest of the activity spread over the length of the strip giving double or triple peaks. For subsequent preparations descending paper chromatography was used to determine the amount of hydrolyzed-reduced Tc and thin-layer chromatography, with acetone as a solvent, to determine the amount of free ToO2 ion, The organ distribution of 99Tcm-glutathione in rats is given in Table 2. As the o/~,dose taken up by the whole organs and the % dose/g of organ are shown. Pancreas accumulation was 2.8 + 0.9% at 30min and 1.5 + 0.2% at 60 min. The pancreas/liver ratio was 5,8 + 1.9 at 30 min and dropped to 2.9 _+ 1.3 at 60 rain. The pancreas/kidney ratio, however, was low (0.81 +0.16 at 30rain and 0.45 _+ 0.12 at 60 min). Scintigraphic studies of One rat showed that the kidneys were well visualized, as expected from the organ distribution studies. The accumulation of the agent by the pancreas was not sufficient for visualization. Dept. of Nuclear Medicine Hacettepe University Medical Centre Ankara, Turkey
MERAL T. ERCAN COSKUN F, BEKDIK TUNCAY SARIZI
References 1. BLAU M. and MANSKE R. F. J. nucL Med. 2. 102 (1961). 2. BLAU M. and BENDER M. A. Radiology 78, 974 (1962). 3. SODEE D. B. Radiology 83, 910 (1964). 4. WAGNER H. N. Principles of Nuclear Medicine, p. 621. Saunders, Philadelphia (1968).
International Journal of Applied Radiation and Isotopes. Vol, 29. pp. 698-700 Pergamon Press Ltd.. 1978. Printed in Great Britain
The Production of High Specific Activity 34mC1- by Fast Neutron Irradiation of Chiorocarbons (Received 25 April 1978) THE YIELDS o f 34mCl- extracted into aqueous solution following 14 MeV neutron irradiation of chlorocarbons is examined as a function of the target composition.
Introduction CHLORINE-34m is a radionuclide (t~ ~ 32.4rain) (') which emits predominantly ~ (145 keV, 47% yield) and /?+ radiation, along with approx 25% yields of ~ emission from the excited state a4S formed. These properties make this an attractive isotope for potential use in in vivo nuclear medicine, as do the chemical properties of the chlorine atom. The isotope may be produced by charged particle bombardment or, as in our laboratory, by the fast neutron (n, 2n) reaction on 35C1.(2) As part of an investigation into the labelling of small molecules with 3a'Cl we required the production of small amounts of high specific activity 34"C1- in aqueous solution. This note reports the yields of 34"C1- obtained following fast neutron bombardment of some chlorine containing compounds and mixtures. In the production of radionuclides following (n, 2n) reactions the separation of the required radioisotope from the parent isotope must rely on the radionuclide being formed in a different chemical form from the inactive parent compound. 13'4) Subsequent separation may then be based on standard techniques such as chromatography or solvent extraction. In seeking a simple system which would provide a reasonable yield of high specific activity 34"C1- it seemed logical to base the separation of 34mC1 from 3sC1 and 37C1 on the fact that recoiling chlorine atoms may react with hydrocarbons and chlorocarbons as shown in (1-4), although undoubtedly many other reactions also occur in such systems.(~-11) 34mC1 + R H - " H - 3 ~ C 1 + R. ---* R - 34~C1 + H. ~4~'CI + R.CI---+ CI34mCl + R. R -- 34"C1 + H.
(1) (2) (3) (4)
Separation of the H aa~C1 and CI 34mC1 from the parent organochlorine compound may then be achieved very simply by extraction with aqueous solutions. The reactions of nucleogenic JaCl with a variety of organic compounds have been studied by STOCKLINet a13~-~) and by KONTIS and URCH.Is-~) The mechanisms of the reactions are clearly not as straightforward as implied by (I-4), and it does not appear possible at present to predict which compound, or mixture of compounds, would be best suited to the production of high specific activity inorganic radiochlorine. The situation with 3arnCl is even less well understood, largely because the isotope has received even less attention,(7) However it does seem clear that simply irradiating a fully chlorinated compound--such as CC14~ does not give rise to a particularly high yield of 34"CI-, The available data suggests that compounds containing H atoms are likely to produce higher inorganic yields. For these reasons we have irradiated several organic compounds and mixtures containing both chlorine and hydrogen in an effort to improve the absolute yield of 3'*mCl-. compared with that obtained from CCI 4.
Experimental Samples consisted of 1.5 ml of liquid in polythene vials. The organic liquids were all standard laboratory grade and, although they were distilled before use, no further purification was undertaken. Samples were irradiated with fast neutrons for ten minutes in batches of three, together with one control sample of CC14, The 14MeV neutron source was the Loughborough University Neutron Generator facility (a Kaman AI003) fitted with a rotating target assembly (Multivolt Ltd.). While the neutron flux varied between different irradiations, by up to a factor of two, the CCI,~ control samples allowed this variation to be taken into account, and the absolute neutron flux was estimated to be of the order of 5 x 10Scm-2/s.
The mixture was stirred for 1-2 rain, then the pH was adjusted to 7 with 0.5 N NaOH. It was passed through a sterile 0.22 /am Millipore membrane filter into a sterile vial. An appropriate amount of sterile 99Tcm (NaTcO4) in 1-2 ml saline was added to the vial and the mixture was shaken for a few seconds.
International Journal of Applied Radiation and Isotopes, VoL 29, pp. 697-698 Pergamon Press Ltd., 1978. Printed in Great Britain
99Tc'-Glutathione:
697
Labelling
and distribution in ram
Chromatography Paper and thin-layer chromatography was used to determine the labelling efficiency and the amount of free pertechnetate and hydrolyzed-reduced technetium in the preparation. For paper chromatography the descending technique, using Whatman No. 3 mm chromatography paper and saline as a solvent, were used. Thin-layer chromatography was performed on Gelman silica gel ITLC-SG strips. The solvents used were acetone, saline, 85% aq. methanol and n-butanol/acetic acid/water (6/2/2). Paper and ITLC strips were scanned on a chromatogram scanner (Actigraph III, Nuclear Chicago) to determine the radioactivity peaks.
(Received 16 February 1978)
Introduction IN rms study glutathione was labelled with 99Tcm in the hope of imaging the pancreas. Selenium-75-selenomethionine is the only radiodiagnostic agent in currently routine use for pancreas scanning,(t-3) however it has obvious drawbacks from the standpoint of the long physical and biological' " half-times. (4)(TI/2P~---120d, Tl/2b = 144d) and the low pancreas uptake.
Biological distribution studies
Materials and methods
Four rats were injected with 0.5 ml ( ~ 200 gCi) 99Tc~ glutathione through the tail vein. Two of them were sacririced after 30 rain and the other two after 60 min. All the organs and the urinary bladder were removed, weighed and counted on a flat-top scintillation counter (Nuclear Chicago) against a standard prepared from a dilution of the injection solution. The percentage dose taken up by each organ and the per cent of the injected dose/g organ were calculated.
Radiolabelling of glutathione Glutathione (crystalline, reduced form) was supplied by Sigma Chemical Company. 99TC' was obtained from a generator (Radiochemical Centre, Amersham, England). The following procedure was used for labelling: 20rag giutathione was dissolved in 2 ml distilled water while stirring. SnCI2.2H20 solution (1 mg/ml) was added (0.5 ml).
TABLE 1, Paper and thin-layer chromatography data of 99Tcm-glutathione Medium
Solvent
RI
% Radioactivity
0 0.90-0.95
0 100
Paper Whatman No. 3 mm
Saline
ITLC-SG
Acetone
Thin-layer Saline 85% aq. methanol n-butanol/a.a.//-I20 (6/2/2)
0 1.0 0 0-1.0 0 0--1.0 0
100 0 10 90 20 80 50
0--1.0
50
TABLE 2. Organ distribution of 99Tc~-glutathione in rats 30 rain Organ Pancreas Liver Spleen Kidney Stomach Intestine Lung Heart Bladder Pancreas/liver Pancreas/kidney
% Dose 2.8 + 0.9 11.0 + 0.2 2.2 + 0.7 17.0 + 0.5 6.1 + 0 . 4 12.6 + 1.1 11.6 + 1.9 2.8 5- 0.1 16.7+0.3
% Dosc/g
60 min
% Dose
8.2 + 2.3 1.5 + 0.2 1.4 + 0.07 13.1 + 1.7 5.8 + 1.3 2.2 5- 0.6 10.1 + 0.8 17.7 + 1.1 2.4+0.04 5 . 4 + 1.2 0.91 + 0.04 13.2 5- 1.1 6.0 + 0.8 !1.3 5- 3.2 6.8 5- 1.6 2.2 + 0.1 4 1 + 10.1 17.6+ 1.1 5.8 5- 1.9 0.81 5- 0.16
~o Dose/g 4.7 + 0.5 1.7 + 0.6 4.3 + 0.1 10.6 5- 1.9 1.8 + 0 . 9 0.85 + 0.20 5.4 + 0.7 3.7 + 0.2 34.9+23.9 2.9 __+1.3 0.45 + 0.12
698
Technical notes
Scintigraphic studies Two rats were injected with 0.5 ml (500/zCi) 99Tt~-glutathione through the tail vein. They were scanned at 15, 30 and 60rain after injection using a Gamma Camera (Nuclear Chicago) and pinhole colimator.
Results and Discussion The paper and thin-layer chromatography results are summarized in Table 1. When descending paper chromatography was used one broad peak was obtained giving a maximum, at Rf 0.90--0.95. This peak contains 99Tc"glutathione, however it might also contain some free TcO2 ion, since TcO£ has an R I value of 0.75-0.80. Lack of radioactivity at the origin indicates that there is no hydrolyzed-reduced technetium. In thin-layer chromatography when acetone was used as a solvent one peak was obtained at the origin. No activity was observed at Rr 1.0 which indicates the absence of free pertechnetate. The other solvent systems failed to separate the complex from the contaminants. Varying amounts of radioactivity were seen at the origin with the rest of the activity spread over the length of the strip giving double or triple peaks. For subsequent preparations descending paper chromatography was used to determine the amount of hydrolyzed-reduced Tc and thin-layer chromatography, with acetone as a solvent, to determine the amount of free ToO2 ion, The organ distribution of 99Tcm-glutathione in rats is given in Table 2. As the o/~,dose taken up by the whole organs and the % dose/g of organ are shown. Pancreas accumulation was 2.8 + 0.9% at 30min and 1.5 + 0.2% at 60 min. The pancreas/liver ratio was 5,8 + 1.9 at 30 min and dropped to 2.9 _+ 1.3 at 60 rain. The pancreas/kidney ratio, however, was low (0.81 +0.16 at 30rain and 0.45 _+ 0.12 at 60 min). Scintigraphic studies of One rat showed that the kidneys were well visualized, as expected from the organ distribution studies. The accumulation of the agent by the pancreas was not sufficient for visualization. Dept. of Nuclear Medicine Hacettepe University Medical Centre Ankara, Turkey
MERAL T. ERCAN COSKUN F, BEKDIK TUNCAY SARIZI
References 1. BLAU M. and MANSKE R. F. J. nucL Med. 2. 102 (1961). 2. BLAU M. and BENDER M. A. Radiology 78, 974 (1962). 3. SODEE D. B. Radiology 83, 910 (1964). 4. WAGNER H. N. Principles of Nuclear Medicine, p. 621. Saunders, Philadelphia (1968).
International Journal of Applied Radiation and Isotopes. Vol, 29. pp. 698-700 Pergamon Press Ltd.. 1978. Printed in Great Britain
The Production of High Specific Activity 34mC1- by Fast Neutron Irradiation of Chiorocarbons (Received 25 April 1978) THE YIELDS o f 34mCl- extracted into aqueous solution following 14 MeV neutron irradiation of chlorocarbons is examined as a function of the target composition.
Introduction CHLORINE-34m is a radionuclide (t~ ~ 32.4rain) (') which emits predominantly ~ (145 keV, 47% yield) and /?+ radiation, along with approx 25% yields of ~ emission from the excited state a4S formed. These properties make this an attractive isotope for potential use in in vivo nuclear medicine, as do the chemical properties of the chlorine atom. The isotope may be produced by charged particle bombardment or, as in our laboratory, by the fast neutron (n, 2n) reaction on 35C1.(2) As part of an investigation into the labelling of small molecules with 3a'Cl we required the production of small amounts of high specific activity 34"C1- in aqueous solution. This note reports the yields of 34"C1- obtained following fast neutron bombardment of some chlorine containing compounds and mixtures. In the production of radionuclides following (n, 2n) reactions the separation of the required radioisotope from the parent isotope must rely on the radionuclide being formed in a different chemical form from the inactive parent compound. 13'4) Subsequent separation may then be based on standard techniques such as chromatography or solvent extraction. In seeking a simple system which would provide a reasonable yield of high specific activity 34"C1- it seemed logical to base the separation of 34mC1 from 3sC1 and 37C1 on the fact that recoiling chlorine atoms may react with hydrocarbons and chlorocarbons as shown in (1-4), although undoubtedly many other reactions also occur in such systems.(~-11) 34mC1 + R H - " H - 3 ~ C 1 + R. ---* R - 34~C1 + H. ~4~'CI + R.CI---+ CI34mCl + R. R -- 34"C1 + H.
(1) (2) (3) (4)
Separation of the H aa~C1 and CI 34mC1 from the parent organochlorine compound may then be achieved very simply by extraction with aqueous solutions. The reactions of nucleogenic JaCl with a variety of organic compounds have been studied by STOCKLINet a13~-~) and by KONTIS and URCH.Is-~) The mechanisms of the reactions are clearly not as straightforward as implied by (I-4), and it does not appear possible at present to predict which compound, or mixture of compounds, would be best suited to the production of high specific activity inorganic radiochlorine. The situation with 3arnCl is even less well understood, largely because the isotope has received even less attention,(7) However it does seem clear that simply irradiating a fully chlorinated compound--such as CC14~ does not give rise to a particularly high yield of 34"CI-, The available data suggests that compounds containing H atoms are likely to produce higher inorganic yields. For these reasons we have irradiated several organic compounds and mixtures containing both chlorine and hydrogen in an effort to improve the absolute yield of 3'*mCl-. compared with that obtained from CCI 4.
Experimental Samples consisted of 1.5 ml of liquid in polythene vials. The organic liquids were all standard laboratory grade and, although they were distilled before use, no further purification was undertaken. Samples were irradiated with fast neutrons for ten minutes in batches of three, together with one control sample of CC14, The 14MeV neutron source was the Loughborough University Neutron Generator facility (a Kaman AI003) fitted with a rotating target assembly (Multivolt Ltd.). While the neutron flux varied between different irradiations, by up to a factor of two, the CCI,~ control samples allowed this variation to be taken into account, and the absolute neutron flux was estimated to be of the order of 5 x 10Scm-2/s.
