Biodistribution of Tc-99m-glutathione in mice with osteosarcoma: effect ofgamma irradiation on tumour uptake

The aim of this study was to determine the efficacy of Tc-99m- glutathione (GSH) in scintigraphic demonstration of osteosarcoma tumour in mice and the effect of gamma irradiation of tumour on tumour uptake of Tc-99m-GSH. The biodistribution of 99mTc-GSH was studied in 30 Balb C mice 3 weeks after is otransplanting osteosarcoma OTS-64 in their thighs. The mice were injected with 400 mu Ci Of (TC)-T-99m-GSH in 0.1 mi through the tail vein. They were equally divided into two groups. Tn the second group the tumours were subj ected to gamma irradiation for 10 min (20 Gy). The mice in both groups were killed at 1, 3 and 6 h. Scintigrams were obtained at each time point. The organs, tumours, some muscle and some blood were removed, weighed and assay ed for radioactivity. Tumour, liver and muscle sections were also obtained for gross autoradiographic studies. The tumours were well visualized on sci ntigrams, The tumour uptake values as a function of time after injection we re 3.27+/-0.80, 1.53+/-0.69, and 1.51+/-0.55 for the control and 5.18+/-1.2 8, 0.399+/-0.120, and 1.67+/-1.05%/g for the irradiated groups at 1, 3 and 6 h, respectively. The tumor-to-muscle concentration ratios were 34.03+/-12 .2, 21.4+/-11.3 and 18.7+/-11.4 for the control and 18.8+/-7.2, 3.63+/-1.9, and 24.1+/-9.0 for the irradiated groups, respectively. The gross autoradi ographic images of tumour sections indicated focal sites of increased uptak e within tumour tissue, indicating the presence of necrotic areas. In concl usion, Tc-99m-GSH accumulated in osteosarcoma and resulted in high tumour-t o-other tissue concentration ratios in mice. The increase in uptake values after tumour irradiation might be a result of increased demand of tumour ce lls for GSH attributable to its well-known biological function as a reducin g agent in addition to increased blood flow and capillary permeability in m alignant tissues.