Lipid peroxidation of erythrocyte membrane induced by xanthine oxidase system: Modification of superoxide dismutase effect by hemoglobin.

Abstract

Lipid peroxidation of [human] 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. 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. The lipid peroxidation was greatly accelerated with increasing concentration of HbO2 up to 2 .mu.M. At concentrations > 2 .mu.M the lipid peroxidation reaction was inhibited. In the presence of 2 .mu.M Hb, addition of superoxide dismutase or scavengers of 1O2 inhibited the lipid peroxidation to the same extent as in while ghosts. In the presence of 10 .mu.M Hb, catalase markedly prevented lipid peroxidation, whereas superoxide dismutase or chemical scavengers of 1O2 had little effect. Catalase was more effective than superoxide dismutase in providing protection against lipid peroxidation induced in the presence of a relatively high concentration of Hb, and the reaction mechanism of O2 radicals with membrane lipids was modified in the presence of Hb.