Antioxidant effect of cupric complex on NADPH-dependent lipid peroxidation in rat liver microsomes.

The antioxidant effect of His-Cu (Histidine and cupric ion) on NADPH-dependent lipid peroxidation was proportional to the inhibitory effect on cytochrome c reduction i the presence of microsomes and ADP-Fe (ADP and ferric ion). The inhibiton of cytochrome c reduction by His-Cu caused no inhibition of NADPH oxidation. ADP-Fe stimulated NADPH oxidation in the absence of cytochrome c, and inhibited cytochrome c reduction. His-Cu inhibited NADPH-oxidation stimulated by ADP-Fe, but the antioxidant effect of His-Cu was independent of the effect on cytochrome b5 reduction. These results suggest that the antioxidant effect of His-Cu depends on the inhibitory effect on the electron transport from NADPH-cytochrome c reductase to ADP-Fe, but not on the inhibitory effect on the activity of the reductase.