Radiation-induced inhibition of human lymphocyte blastogenesis: the effect of superoxide dismutase and catalase

Mitogen-induced lymphocyte blastogenesis was measured following X-irradiation (0-4 Gy) in the presence or absence of superoxide dismutase (SOD), under aerobic and anaerobic conditions. There were no significant differences between radiation survival curves under these different conditions, nor did SOD have any radioprotective effect. This demonstrates lack of oxygen dependence of radiation-induced inhibition of lymphocyte blastogenesis. Following X-irradiation at 2 Gy, neither SOD nor catalase, alone or together, added before or after irradiation, were radioprotective. In comparison to controls, both enzymes depressed lymphocyte proliferation when added at levels as low as 25 μg catalase or 100 μg SOD/ml media. When SOD and catalase were added together, the greatest depression of blastogenesis was obtained with increasing levels of SOD relative to increasing levels of catalase, indicating that SOD was largely responsible for this depression. The suppressive effect of administration of SOD (p < 0.05), catalase (p < 0.001) and SOD + catalase (p < 0.001) on lymphocyte division was significantly greater when given prior to X-irradiation. The lack of an oxygen effect and the inability of SOD and catalase to protect human lymphocytes from X-irradiation suggests that O2-and/or H2O2 are not involved in radiation-induced inhibition of lymphocyte blastogenesis. (author)