Inhibition by sodium citrate on 67Ga adsorption to various materials

The adsorption of 67Ga to the inner surface of stainless steel, polyethylene and silicone tubings was studied. The three tubings remarkably adsorbed 67Ga in order of stainless steel, silicone and polyethylene tubing. Sodium citrate inhibited the adsorption of 67Ga in a dose-dependent manner. These phenomena were also observed in blood sampling via the catheter inserted into the external jugular vein. These results show that constant concentration of sodium citrate is necessary for the in vitro study of 67Ga in order to prevent the adsorption to the surface of experimental materials.     

Binding of 67 Ga and 59 Fe to ferritin or transferrin

The bindings of 67Ga and 59Fe to ferritin or transferrin in vitro has been investigated. Affinity constants have been measured using the equilibrium dialysis, and the results have been obtained as follows: 1 Apo-ferritin could not bind to 67Ga until it was transformed into ferritin in presence of Fe-citrate. On the contrary, the affinity of 67Ga to ferritin was reduced when Fe was released from ferritin; thus indicating that Fe-core has been required for the binding of 67Ga to ferritin. 2 Binding of 67Ga to ferritin was inhibited with apo-transferrin, and this was also shown in the case of 59Fe. In the presence of NaHCO3 or citrate, more remarkable inhibitions were observed. NaHCO3 or citrate was found to give a synergistic effect on the binding of 67Ga to transferrin, as well as Fe-transferrin. Therefore, both 67Ga and 59Fe could not bind to ferritin in the state of 67Ga- or 59Fe-transferrin. 3 The release of 59Fe from 59Fe-transferrin was enhanced with adenosine triphosphate (ATP), citrate, or ascorbic acid, while any of these reagents did not affect the release of 67Ga from 67Ga-transferrin. The comparison of 59Fe and 67Ga through their bindings to ferritin or transferrin has suggested one of points to distinguish 67Ga from 59Fe in the cell.     

A case of parathyroid carcinoma visualized by 67Ga citrate and 201Tl chloride scintigraphy

Both 67Ga citrate and 201Tl chloride accumulated in a parathyroid tumor of a 62 year-old woman with primary hyperparathyroidism. Histological studies disclosed that the tumor was a parathyroid carcinoma. The use of both tumor scanning agents, 67Ga citrate and 201Tl chloride to visualize parathyroid carcinoma in a patient with primary hyperparathyroidism has not been reported as far as we could determine.     

Ga-labeling of immunoglobulin G with high specific radioactivity

To obtain radiogallium labeled immunoglobulin G with a high specific radioactivity for in vitro use, a 67Ga source was purified by extraction from 67Ga-gallium citrate with butyl acetate, and a 67Ga-labeling solution was produced. This solution was then used to label a deferoxamine-immunoglobulin G conjugate. Both a very high specific radioactivity (872 +/- 56 MBq/mg) and a high labeling efficiency (94.0%) were achieved.     

TUMOR IMAGING WITH [111niIn]MONO-DTPA-ETHYLENEGLYCOL-Ga-DEUTEROPORPHYRIN

Abstract Mono-DPTA-ethyleneglycol-Ga-deuteroporphyrin (MDEGD) was synthesized, by coordinating non-radioactive Ga in the porphyrin ring and connecting DTPA (diethylene-triamine-N,N,N,N,N,-pentaacetic acid) to its side chain. By labeling with 111_In, chemicals for scintigraphy were developed. They were applied to Syrian golden hamsters with implanted pancreatic gland cancers and C57-black mice with Lewis lung cancer to enable tumor imaging and biodistribution examination. A comparative study was also conducted with [⁶⁷Ga]citrate. In the resultant data, [¹¹¹In]MDEGD showed larger tumor/lung, tumor/kidney and tumor/blood ratio with [⁶⁷Ga]citrate. The affinity of [ⁿIn]MDEGD in inflammatory tissue was much lower than that of ⁶⁷Ga citrate. [¹¹¹In]MDEGD lost its photosensitivity.     

Influence of the particle size of activated charcoal on labeling efficiency with 67Ga-citrate for colonic transit study

Indium-111 and ^99mTc have been proposed for colonic transit study, but ¹¹¹In is expensive and the half-life of ^99mTc is too short for the study. Gallium-67 citrate is inexpensive and has a suitable half-life. In our previous study, we successfully labeled ⁶⁷Ga-citrate activated charcoal, and the labeling efficiency exceeded 91% after a 96 hour incubation period. In this work, we evaluated the influence of the size of activated charcoal particles on the labeling efficiency with ⁶⁷Ga-citrate. The data showed that the influence of particle size on the labeling efficiency of activated charcoal with ⁶⁷Ga was insignificant. Both sizes of activated charcoal particles can be used for labeling with ⁶⁷Ga in colonic transit study.     

Uptake of 67Ga into the rat liver after treatment with thioacetamide

67Ga uptake of the liver began to elevate from the 1st day and reached a maximum at the 2nd day of treatment with thioacetamide (TIAA). Incorporation of 3H-thymidine into the liver DNA fraction was reached a maximum at the 1.5th day, and the value was 5.7 times of the control. The uronic acid content and 35S incorporation in the 1.2 M NaCl-soluble fraction which contained predominantly heparan sulfate (HS), were both peaked at the 2nd day. These patterns were in good agreement with that of 67Ga uptakes in the liver treated with TIAA. Pretreatment of aminoacetonitrile, an inhibitor of fibrosis, was effective in lowering the elevated uptake of 67Ga in TIAA-treated rat liver. Uptake of the 67Ga in the TIAA-treated liver was also inhibited when they were treated with cycloheximide, an inhibitor of protein synthesis. On the other hand no significant inhibition was observed in the cytosine arabinoside-treated-TIAA rats. These results suggest that HS may be involved in the 67Ga uptake in damaged liver, and that relation between 67Ga uptake and cell proliferation is secondary.     

Sorption of microamounts of gallium(III) on Fe(OH)3 and Fe2O3 precipitates

Summary The sorption of microamounts of gallium(III) on Fe(OH)₃ and Fe₂O₃ precipitates was studied by using⁶⁷Ga as radioactive indicator. The dependence of sorption of microamounts of gallium(III) on pH, sorbent concentration, and duration of the contact between gallium-(III) and Fe(OH)₃ precipitate, was established. In the presence of sodium citrate the sorption of microamounts of gallium (III) on Fe₂O₃ markedly decreased. Iron(III) hydroxide and Fe₂O₃ precipitates are suitable collectors for the preconcentration of gallium (III) traces in solution.

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Zusammenfassung Die Adsorption von Mikromengen Ga(III) an Niederschlägen von Fe(OH)₃ und Fe₂O₃ wurde mit Hilfe von⁶⁷Ga als radioaktivem Indikator untersucht. Die Abhängigkeit der Adsorption vom pH, von der Konzentration des Sorptionsmittels und von der Dauer des Kontakts zwischen Ga(III) und Fe(0H)₃ wurde festgestellt. In Gegenwart von Na-Citrat wird die Sorption an Fe₂O₃ merklich geringer. Eisen (III)hydroxid- und Fe₂O₃-Niederschläge eignen sich als Kollektoren zur Anreicherung von Ga(III)-Spuren in einer Lösung.

     

Effect of gallium nitrate on the in vivo distribution of 67Ga in rats bearing inflammatory lesions

Effect of gallium nitrate on the pharmacokinetics and tissue accumulation of 67Ga was investigated in rats bearing turpentine oil-induced abscess. Gallium nitrate accelerated the blood disappearance of 67Ga, but this effect was less potent than that of ferric nitrate. The accumulation of 67Ga in liver was significantly lowered by gallium nitrate, but no significant decrease of 67Ga accumulation in abscess was observed. On the other hand, 67Ga accumulation in bone was slightly facilitated by gallium nitrate. Ferric nitrate exerted a similar effect on tissue accumulation of 67Ga as gallium nitrate.     

Kinetics of Ga(NOTA) formation from weak Ga-citrate complexes

Gallium complexes are gaining increasing importance in biomedical imaging thanks to the practical advantages of the (68)Ga isotope in Positron Emission Tomography (PET) applications. (68)Ga has a short half-time (t(1/2) = 68 min); thus the (68)Ga complexes have to be prepared in a limited time frame. The acceleration of the formation reaction of gallium complexes with macrocyclic ligands for application in PET imaging represents a significant coordination chemistry challenge. Here we report a detailed kinetic study of the formation reaction of the highly stable Ga(NOTA) from the weak citrate complex (H(3)NOTA = 1,4,7-triazacyclononane-1,4,7- triacetic acid). The transmetalation has been studied using (71)Ga NMR over a large pH range (pH = 2.01-6.00). The formation of Ga(NOTA) is a two-step process. First, a monoprotonated intermediate containing coordinated citrate, GaHNOTA(citrate)*, forms in a rapid equilibrium step. The rate-determining step of the reaction is the deprotonation and slow rearrangement of the intermediate accompanied by the citrate release. The observed reaction rate shows an unusual pH dependency with a minimum at pH 5.17. In contrast to the typical formation reactions of poly(amino carboxylate) complexes, the Ga(NOTA) formation from the weak citrate complex becomes considerably faster with increasing proton concentration below pH 5.17. We explain this unexpected tendency by the role of protons in the decomposition of the GaHNOTA(citrate)* intermediate which proceeds via the protonation of the coordinated citrate ion and its subsequent decoordination to yield the final product Ga(NOTA). The stability constant of this intermediate, log K(GaHNOTA(citrate)*) = 15.6, is remarkably high compared to the corresponding values reported for the formation of macrocyclic lanthanide(III)-poly(amino carboxylates). These kinetic data do not only give mechanistic insight into the formation reaction of Ga(NOTA), but might also contribute to establish optimal experimental conditions for the rapid preparation of Ga(NOTA)-based radiopharmaceuticals for PET applications.     

Comparative pharmacokinetics of 67Ga among the different routes of injection

The pharmacokinetic study of 67Ga-citrate (67Ga) following intravenous (i.v.), subcutaneous (s.c.) and intraperitoneal (i.p.) injection was performed in anesthetized rats using the repeated blood sampling method by cannulation technique into the external jugular vein. The disappearance of 67Ga from the blood following i.v. and s.c. injection was best fit a three-exponential equation. There was no significant difference between the areas under the curves following i.v. and s.c. injection of 67Ga. In the case of i.p. injection, the disappearance of 67Ga from the blood was described by a two-exponential equation. However, the maximum blood radioactivity was very low, and the disappearance rate of 67Ga from the blood was extremely slow compared to the other routes of injection. The conclusion from these results was that s.c. injection was as suitable as i.v. injection, but i.p. injection was not appropriate for the distribution study of 67Ga such as scintigraphy or autoradiography. However, i.p. route may be available for a special experiment which needs the long-time retention of 67Ga in the blood.     

The influences of dexamethasone and indomethacin on 67Ga uptake by normal tissues

Dexamethasone (DEX) increased 67Ga uptake by the liver and spleen at 4, 8, and even 24 h after the injection of 67Ga. These results showed that DEX influenced 67Ga accumulation as well as the initial entry of 67Ga in the liver and spleen. On the other hand, indomethacin (IM) decreased 67Ga uptake by the liver and spleen at 4 h after the injection of 67Ga but did not influence the uptake at 8 or 24 h after the injection of 67Ga. Moreover, DEX or IM little influenced 67Ga uptake by the kidney and muscle. These results suggest that the influence of DEX or IM on 67Ga uptake or accumulation is specific for the liver and spleen.     

The difference between the mechanism of 67Ga accumulation and 59Fe accumulation in cultured tumor cells

It is well known that the mechanism of 67Ga accumulation into tumor cells is mediated with transferrin receptor as well as iron. The present study was designed to explore the difference between the mechanism of gallium accumulation and that of iron by using mouse leukemic cell line L5178Y. When monensin which inhibits the recycle of transferrin receptor was added to the incubated system, accumulation of 59Fe and 67Ga was clearly diminished compared with that of control. However, inhibition of 59Fe accumulation was more remarkable than that of 67Ga. Furthermore, monensin has a action of Na+ ionophore which decreases Na+ gradient between the inside and the outside of the plasma membrane. Following administration of monensin, 67Ga accumulation was diminished according to the loss of the Na+ gradient. On the other hand, following administration of valinomycin, 67Ga accumulation was not affected by the loss of the K+ gradient. From these results, it was suggested that the mechanism of 67Ga accumulation into tumor cells differed from that of 59Fe and transferrin receptor and Na+ gradient of tumor cells played an important role on 67Ga accumulation into tumor cells.     

Mechanism of 67Ga uptake by an experimental abscess--permeability of plasma from blood vessels in abscessed tissue

In the previous paper, we reported that 67Ga was accumulated in abscess and uptake rate of 67Ga in abscess increased with time after the injection of 67Ga-citrate. The present study was undertaken to elucidate the influence of blood flow on the accumulation of 67Ga in abscess. Five days after subcutaneous injection of 0.2 ml of turpentine to the rats, 131I-human serum albumin (HSA) was injected intravenously to the rats. At an appropriate time after the injection (10 min to 6 days), uptake rates of 131I-HSA in abscess and normal tissues were measured. Similarly, 51Cr-red blood cells (RBC) were injected intravenously to the above rats and the uptake rates of 51Cr-RBC were also measured. One, three, and 24 hours after injection of 131I-HSA, the uptake rates of 131I-HSA in abscess were 1.32 %dose/g, 1.84 %dose/g, and 0.82 %dose/g, respectively. However, the uptake rates of 51Cr-RBC in abscess was very small, and the value was 0.14 %dose/g at 24 hours after the injection. In the case of abscess, blood in the tissue fluid was very little, but the permeability of 131I-HSA from the blood vessel in the tissue was much larger than that of normal tissues. From these facts, it was deduced that the accelerated permeability caused the abscess accumulation of 67Ga.     

Kinetics of metal ion exchange between citric acid and serum transferrin

The exchange of Fe(3+), Tb(3+), In(3+), Ga(3+), and Al(3+) between the C-terminal metal-binding site of the serum iron transport protein transferrin and the low-molecular-mass serum chelating agent citrate has been studied at pH 7.4 and 25 degrees C. The removal of Ga(3+), In(3+), and Al(3+) follows simple saturation kinetics with respect to the citrate concentration. In contrast, removal of both Fe(3+) and Tb(3+) shows a combination of saturation and first-order kinetic behavior with respect to the citrate concentration. The saturation component is consistent with a mechanism for metal release in which access to the bound metal is controlled by a rate-limiting conformational change in the protein. The first-order kinetic pathway is very rapid for Tb(3+), and this is attributed to a direct attack of the citrate on the Tb(3+) ion within the closed protein conformation. It is suggested that this pathway is more readily available for Tb(3+) because of the larger coordination number for this cation and the presence of an aquated coordination site in the Tb(3+)-CO(3)-Tf ternary complex. There is relatively little variation in the k(max) values for the saturation pathway for Tb(3+), Ga(3+), Al(3+), and In(3+), but the k(max) value for Fe(3+) is significantly smaller. It is suggested that protein interactions across the interdomain cleft of transferrin largely control the release of the first group of metal ions, while the breaking of stronger metal-protein bonds slows the rate of iron release. The rates of metal binding to apotransferrin are clearly controlled in large part by the hydrolytic tendencies of the free metal ions. For the more amphoteric metal ions Al(3+) and Ga(3+), there is rapid protein binding, and the addition of citrate actually retards this reaction. In contrast, the nonamphoteric In(3+) ion binds very slowly in the absence of citrate, presumably due to the rapid formation of polymeric In-hydroxo complexes upon addition of the unchelated metal ion to the pH 7.4 protein solution. The addition of citrate to the reaction accelerates the binding of In(3+) to apoTf, presumably by forming soluble, mononuclear In-citrate complexes.     

Double tracer autoradiography of bone tumor using 3H-thymidine and radionuclides for diagnostic purpose

Whole body distribution and accumulation of radionuclide for diagnostic purpose such as 99mTc-MDP (methylene diphosphonate), 67Ga-citrate (67Ga) and 201Tl-chloride (201Tl) in implanted osteosarcoma of human origin were evaluated by macroautoradiography of Balb/c nude mouse. 3H-thymidine of which uptake has a close relation to growth pattern of tumors was used for a partner of target nuclide in double tracer technique to examine the distribution characteristics. Separated distribution pattern of coupled nuclides was imaged by a difference both of half life and energy of radiation between radionuclides. The distribution pattern of each target nuclide and 3H-thymidine were compared to clarify distribution characteristics respectively in specimen. 67Ga and 201Tl were taken around the tumor and the mode of their distribution was identical to that of 3H-thymidine. Uptake of 67Ga in tumor was much higher. 99mTc-MDP accumulated in the central zone of the tumor and its pattern was quite different from that of 3H-thymidine. From above result it was demonstrated that the accumulation mechanism of 67Ga, 201Tl and 99mTc-MDP are quite different in the tumor each other. So we concluded that our method of double tracer technique was useful for evaluation of distribution pattern of radionuclides for diagnostic purpose.     

Simultaneous determination of zinc,iron and chlorides in radiopharmaceutical gallium /67Ga/ citrate injections by FSDP or DP polarography

A method for simultaneous determination of traces of zinc, iron, and chloride ions by fast scan or ordinary differential pulse polarography has been proposed. The method is especially suited to check the purity of radiopharmaceutical gallium /⁶⁷Ga/ citrate injections. The interference of citrate ions was eliminated by using a complex-forming base electrolyte containing triethanolamine and ammonia. The relative standard deviation of the determination of iron, zinc, and Cl^– ions in the range of 0.05–1.00 g of Fe or Zn and 3–25 g of Cl^– per ml solution was found to be 5–10%.     

Distribution of 67Ga-citrate in 3'-methyl-4-dimethylaminoazobenzene-induced hepatoma of rats

The distribution of 67Ga-citrate in the hepatoma of rat induced by 3'-methyl-4-dimethylaminoazobenzene was studied. 67Ga uptake ratio resected specimen, autoradiography and histological specimen were compared each other. 67Ga uptake ratio of the tumor was increased 1.6 to 7.2 times (average 4.4) to control group. Regardless of the size of the tumor, macroautoradiographically observed distribution of 67Ga-citrate in the hepatoma was higher in the peripheral zone than in the central zone. Histologically the degeneration of tumor cell was low or absent in the peripheral zone of tumor, whereas it was intense in the central zone. 67Ga-citrate was highly accumulated in the zone which the degeneration was low or absent. We, however, could not demonstrate the site where 67Ga-citrate was incorporated.     

Photonuclear production of carrier-free radionuclides: 69mZn

Russian Chemical Bulletin - The yields of 66Ga, 67Ga, 68Ga, 70Ga, 65Zn, and 69mZn upon irradiation of gallium with the natural isotopic composition by the bremsstrahlung photon beam with the energy...     

Study of 67Ga distribution in neoplasms and in liver by a cell fractionation method]

Subcellular distribution of 67Ga was quantitatively determined to evaluate the role of lysosome in accumulation of 67Ga in malignant tumor tissue and liver. The following animals and transplanted tumors were used: rats implanted with Yoshida sarcoma and hepatoma AH109A; mice implanted with Ehrlich tumor. 67Ga-citrate were injected to the rats intravenously and to the mice intraperitoneally. Ten minutes to 48 hours after the administration of 67Ga-citrate, the animal were sacrificed, and the tumor tissues and liver were excised. Subcellular fractionation of tumor tissues and livers were carried out according to the method of Hogeboom and Schneider. Radioactivity of each fraction was counted by a well type scintillation counter, and protein of each fraction was measured according to Lowry's method. In Yoshida sarcoma and Ehrlich tumor, most of the radioactivity was localized in the supernatant fraction, and small amount of radioactivity was localized in the mitochodrial fraction (lysosome contains in this fraction). But in the liver, most of the radioactivity was concentrated in the mitochondrial fraction and the radioactivity of this fraction was increased with the passage of time after administration. Twenty-four hours later, about 50% of total radioactivity was accumulated in this fraction. In the case of hepatoma AH109A, radioactivity of mitochondrial fraction was increased with the passage of time after administration, and about 30% of total activity was concentrated in this fraction at 24 hours after administration. From these results it is concluded that lysosome doses not play an important role in the tumor concentration of 67Ga and lysosome plays an important role in the liver concentration of 67Ga. In the case of hepatoma AH109A it is presumed that lysosome plays considerably important role in the tumor concentration of 67Ga, hepatoma AH109A having some nature of liver.