Radiation-induced Lipid Peroxidation and Membrane-bound Enzymes in Liver Microsomes

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Abstract
Changes in lipid peroxidation and enzymes in rat liver microsomes were examined after .gamma.-irradiation. The radiation-induced lipid peroxidation was increased with increasing radiation dose, decreasing dose-rate and decreasing concentration of microsomes. The content of cytochrome P-450 was decreased with decreasing dose-rate and inversely with radiation dose; NADPH-cytochrome c reductase and cytochrome b5 were less affected by .gamma.-irradiation. The lipid peroxidation and the inactivation of microsomal enzymes induced by .gamma.-irradiation were markedly reduced by radical scavengers. Hexobarbital hydroxylating activity and binding capacity of P450 for hexobarbital, which were strikingly decreased after .gamma.-irradiation, were less protected by radical scavengers than the lipid peroxidation and inactivation. Intrinsic enzymes apparently are more damaged through radiation-induced peroxidation of membrane lipids as compared with extrinsic enzymes.