Tumor and liver uptake models of 67Ga-citrate

Tumor uptake of 99mTc-MIBI and 201Tl by a 9L gliosarcoma brain tumor model in rats

There have been several recent case reports of the accumulation of 99mTc-MIBI [hexakismethoxyisobutylisonitriletechnetium(I), Cardiolite, Sestamibi] in tumors, but no reports of the uptake of this radiopharmaceutical in an animal model. To address this question, the biodistributions of 99mTc-MIBI and 201Tl were compared in Fisher rats bearing 9L gliosarcomas. The results showed that, although the absolute uptake of the tracers by the tumor is relatively low (< 1% ID/g), the tumor-to-normal brain ratios are greater than 6:1 because of low uptake by normal brain. The tumor-to-normal brain ratio of 99mTc-MIBI exceeds that of other currently available 99mTc radiopharmaceuticals suggesting that 99mTc-MIBI may be of particular value in the clinical evaluation of brain tumors and that further investigation of this class of compounds as tumor-avid radiopharmaceuticals is necessary.

Determination of the lysosomal role in tumor accumulation of 67Ga by dual-tracer studies

The lysosomal role in tumor accumulation of 67Ga was determined by dual-tracer (67Ga and 46Sc) studies. It became clear that 67Ga essentially did not accumulate in the tumor lysosome, and that the lysosome did not play a major role in tumor accumulation of 67Ga. In addition, it was revealed that tumor lysosome was hardly disrupted at all in some phases of fractionation procedures.

Distribution of 103Ru-chloride in tumor-bearing animals and the mechanism for accumulation in tumor and liver

Tumor uptake rates of 103Ru-chloride were smaller than those for 67Ga-citrate. In three tumors and liver, 103Ru in the mitochondrial fraction containing lysosome increased with time after the administration of 103Ru-chloride. The concentration of 103Ru was more dominant in connective tissue (especially inflammatory tissue) than in viable tumor tissue or in necrotic tissue. Quite large amounts of 103Ru in the tumor and liver were bound to the acid mucopolysaccharide whose molecular masses exceeded 40,000. Behavior of this nuclide was essentially similar to that of 67Ga.

67Ga accumulation in inflammatory lesion and its mechanism: comparison with malignant tumor

The accumulation of 67Ga in inflammatory lesions increased with time after injection of turpentine oil and reached a plateau 5 days later. At that time the uptake in the lesions was larger than any other tissue, after ten days the lesion uptake decreased. In experiments using rats which had been kept for 5 days after subcutaneous injection of turpentine oil, the accumulation of 67Ga in inflammatory lesions increased with time until six days after administration of 67Ga-citrate. It is clear from this study that 67Ga is avidly accumulated in areas where the subcutaneous tissue is infiltrated with neutrophils and macrophages, that it is not accumulated at the sites in which neutrophils are crowded, that nuclear material, mitochondria, lysosomes and microsomes do not play a major role in 67Ga accumulation in the lesion and that the main binding acid mucopolysaccharide in the lesion is a acid mucopolysaccharide which is none of the following: keratan sulfate, heparan sulfate, heparin, or chondroitin sulfate A, B or C. It is presumed that the main 67Ga binding acid mucopolysaccharide is keratan polysulfate (or other oversulfated acid mucopolysaccharides).