Effect of NADPH on the microsomal lipid peroxidation in the presence of the soluble fraction of rat liver (author's transl)

Abstract

Effect of NADPH on lipid peroxidation in microsomes with the soluble fraction of rat liver was investigated. NADPH was found to inhibit lipid peroxidation in 9000×g supernatant fraction when over a certain amount of the fraction was added to the reaction mixture, even in the presence of Fe2+ or Fe2+-ADP which is known to activate the microsomallipid peroxidation induced by NADPH. In addition, the soluble fraction-stimulated lipid peroxidation in microsomes was found to be effectively inhibited by NADPH in the presence of a certain amount of the soluble fraction. NADPH extended the duration of depressing the lipid peroxidation in 9000×g supernatant fraction followed by a rise in the formation of lipid peroxides. When Zn2+, an inhibitor of glutathione reductase, was added to 9000×g supernatant fraction or the soluble fraction-microsomes system, lipid peroxide formation was not depressed by the addition of NADPH. Inversely, the addition of GSSG to the soluble fraction-microsome system was found to enhance the antiperoxidative effect of NADPH. These results indicate that a factor, which participates in the inhibitory action of NADPH on the microsomal lipid peroxidation in the presence of the soluble fraction, may be a glutathione reductase system present in the soluble fraction. Therefore, it is thought that NADPH does not only stimulate the microsomal lipid peroxidation, but also acts as an inhibitory factor on the lipid peroxide formation in microsomes together with the soluble fraction.