Antioxidative effect of protoporphyrin on lipid peroxidation in rat liver subcellular fractions.

Abstract

The effect of protoporphyrin IX (PP) on lipid peroxidation was investigated in rat liver homogenates, in hepatic subcellular organelles such as mitochondria and microsomes, and in a mixture of unsaturated fatty acids. PP inhibited both the Fe2+ and ascorbic acid (AsA)-stimulated lipid peroxidation and the concomitant increase of oxygen consumption in the homogenates. PP failed to inhibit auto-oxidation in the mixture of unsaturated fatty acids. PP inhibited the lipid peroxidation both in mitochondria stimulated by AsA and in microsomes stimulated by AsA or a reduced nicotinamide adenine dinucleotide phosphate-generating system. Its antioxidative effects were less pronounced in heat-denatured subcellular fractions. Soluble fraction (SF) enhanced the antioxidative action of PP on the lipid peroxidation in boiled microsomes, but boiled SF lessened the action of PP. These findings indicate that PP has an autoxidation effect on lipid peroxidation in liver, and that the antioxidative effect of PP is measured by factos present in liver, some of which are heat-labile and some heat-stable.