Possible role of elevation of glutathione in the acquisition of enhanced proliferation of mouse splenocytes exposed to small-dose γ-rays

Purpose: To examine the relation between the induction of an increased glutathione level and the elevated proliferative response of mouse splenocytes by a small dose of γ-rays. Materials and methods: Male ICR strain mice, 7 weeks of age, were divided into irradiated and non-irradiated control groups. Irradiation was done with γ-rays from ¹³⁷Cs source at a dose of 50 cGy (1.11 Gy/min). Glutathione content in the splenocytes was measured using a modified spectrophotometric technique. Concanavalin A (Con A)-induced proliferative response of the splenocytes after whole-body γ-ray irradiation was estimated from the ³H-thymidine incorporation into the cells. Results: The glutathione level in mouse splenocytes increased 2 h after whole-body γ-ray irradiation at 50 cGy, peaked at 4 h and thereafter decreased almost to the zero-time level by 12-h post-irradiation. A significant enhancement of Con A-induced proliferation was observed in the splenocytes obtained from the wholebody-irradiated animals between 2 h and 6 h post-irradiation. Glutathione exogenously added to splenocytes obtained from normal mice enhanced the Con A-induced proliferation of splenocytes in a dose-dependent manner. This enhancement was completely blocked by buthionine sulfoximine, a specific inhibitor of the de novo pathway of glutathione synthesis. Conclusions: The induction of endogenous glutathione immediately after low-dose γ-ray irradiation is at least partially responsible for the enhancement of immune function, and may throw light on the mechanisms of carcinostatic effects induced by low dose ionizing radiation.