BIODISTRIBUTION OF 99mTc-GLUTATHIONE IN MICE WITH OSTEOSARCOMA: EFFECT OF GAMMA IRRADIATION ON TUMOR UPTAKE

Meral T. ERCAN*°, Reingard SENEKOWITSCH-SCHMIDTKE**, Sabine BERNATZ**

*Department of Nuclear Medicine, Faculty of Medicine, Hacettepe University, 06100 Sihhiye, Ankara, TURKEY. **Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar der Technischen Universität München, GERMANY.
°Corresponding Author

Summary :
The aim of this study was to determine the efficacy of 99mTc-glutathione (GSH) in scintigraphic demonstration of osteosarcoma tumor in mice and the effect of gamma irradiation of tumor on tumor uptake of 99mTc-GSH. The biodistribution of 99mTc-GSH was studied in 30 Balb C mice three weeks after implanting osteosarcoma tumor in their thighs. The mice were injected with 400 µCi of 99mTc-GSH in 0.1 ml through the tail vein. They were divided into 2 equal groups. The tumors of mice in the second group were subjected to gamma irradiation for 10 min (20 Gy). The mice in both groups were sacrificed at 1, 3 and 6 h. Scintigrams were obtained at each time point. The organs, tumors, some muscle and some blood were removed, weighed and assayed for radioactivity. Tumor, liver and muscle sections were also obtained for gross autoradiographic studies. The tumors were well visualised on scintigrams. The tumor uptake values were 3.27±0.80, 1.53±0.69, and 1.51±0.55 for the control and 5.18±1.28, 0.399±0.120, and 1.67±1.05 %/g for the irradiated groups, respectively. Tumor/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 irradiated groups, respectively. Gross autoradiography of tumor sections indicated focal sites of increased uptake within tumor tissue, indicating the presence of necrotic areas. In conclusion, 99mTc-GSH accumulated in osteosarcoma tumor and resulted in high tumor to other tissue concentration ratios. The increase in uptake values after tumor irradiation might be a result of higher demand of tumor cells for GSH, due to formation of free radicals and oxidants as by-products of irradiation.

Key words:
99mTc-Glutathione, Osteosarcoma, Gammairradiation, Autoradiography.