Selenite-induced variation in glutathione peroxidase activity of three mammalian cell lines: no effect on radiation-induced cell killing or DNA strand breakage.

The selenium-dependent glutathione peroxidase activities of three mammalian cell lines, HT29, P31, and N-18, cultured in medium with low serum content, increased about 2-, 5-, and 40-fold, respectively, after supplementation with 100 nM selenite. Catalase, CuZn superoxide dismutase, and Mn superoxide dismutase activities were not generally influenced by selenite supplementation, and there was only a minor nonselenium-dependent glutathione peroxidase activity in the investigated cell lines. Gamma-irradiated control and selenite-supplemented cells showed no changes in the surviving fractions, as estimated by clonogenic survival or [3H]-thymidine uptake, nor were there any significant differences between the two groups in the induction of DNA strand breaks after gamma irradiation under repairing (37 degrees C) or nonrepairing (0 degrees C) conditions. The results suggest that selenium-dependent glutathione peroxidase does not contribute significantly to the radiation resistance of cultured mammalian cells.