Lipid Peroxidation of Erythrocyte Membrane induced by Xanthine Oxidase System : Modification of Superoxide Dismutase Effect by Hemoglobin

Abstract

Lipid peroxidation of erythrocyte ghosts was caused by incubation in a xanthine oxidase system. Addition of superoxide dismutase to this system strongly inhibited the lipid peroxidation, implying that O₂-is an essential intermediate in the lipid peroxidation reaction. However, catalase did not inhibit but greatly promoted the lipid peroxidation, suggesting that catalase enhances net O₂-production through the stabilization of xanthine oxidase. Chemical scavengers of singlet oxygen (¹O₂) inhibited the peroxidation reaction, suggesting that the extremely reactive radical of ¹O₂ may be produced from O₂-generated by the xanthine oxidase system. Hydroxyl radical scavengers were without effect. Furthermore, the lipid peroxidation was greatly accelerated with increasing concentration of oxyHb up to 2μM. At concentrations above 2μM, however, the lipid peroxidation reaction was inhibited. In the presence of 2μM Hb, addition of superoxide dismutase or scavengers of ¹O₂ inhibited the lipid peroxidation to the same extent as in white ghosts. In the presence of 10μM Hb, however, catalase markedly prevented lipid peroxidation, whereas superoxide dismutase or chemical scavengers of ¹O₂ had little effect. These results indicate that catalse was more effective than superoxide dismutase in providing protection against lipid peroxidation induced in the presence of a relatively high concentration of Hb and that the reaction mechanism of oxygen radicals with membrane lipids was modified in the presence of Hb.