Radiation-induced lipid peroxidation and membrane-bound enzymes in liver microsomes

Changes in lipid peroxidation and enzymes in liver microsomes were examined after alpha-irradiation. The radiation-induced lipid peroxidation was increased with increasing radiation dose, with decreasing dose-rate and also with decreasing concentration of microsomes. The content of P-450 was decreased with decreasing dose-rate and inversely with radiation dose, while NADPH-cytochrome c reductase and cytochrome b5 were less affected by alpha-irradiation. Both the lipid peroxidation and the inactivation of microsomal enzymes induced by alpha-irradiation were mardedly reduced by radical scavengers. Hexobarbital hydroxylating activity and binding capacity of P-450 for hexobarbital, which were strikingly decreased after alpha-irradiation were less protected by radical scavengers, in contrast to the case of the lipid peroxidation and of the enzymes. These results suggest that intrinsic enzymes are more damaged through radiation-induced peroxidation of membrane lipids as compared with extrinsic enzymes.