The influence of phospholipase A2 and glutathione peroxidase on the elimination of membrane lipid peroxides

Abstract

The relationship between release of membrane lipid peroxidation products and phospholipase action was examined. Rat liver microsomes and phosphatidylcholine liposome-phospholipase A2 preparations were subjected to iron ascorbate-induced lipid peroxidation. Peroxidation products were characterized by measurement of malondialdehyde and lipid peroxides. Experiments were designed to demonstrate phospholipase dependent removal of peroxidation products origination in the membrane. Increased lysophosphatidylcholine formation was evident following lipid peroxidation in phospholipase A2-containing liposomes which was inhibited by p-bromophenacyl bromide and mepacrine. Lipoxygenase-dependent oxygen consumption, as well as peroxide transfer from microsomes to the incubation medium, was largely dependent on phospholipase and could be diminished by phospholipase inhibitors. Furthermore, lipid hydroperoxides formed by subjecting phosphatidylcholine liposomes to iron ascorbate-induced peroxidation, or those present in aged liposomes, were effectively reduced by glutathione peroxidase when phospholipase A2 was present in the assay. Low level glutathione peroxidase activity was observed in the absence of phospholipase A2.