Superoxide and hydrogen peroxide-dependent lipid peroxidation in intact and triton-dispersed erythrocyte membranes

Isolated erythrocyte membranes incubated with xanthine, xanthine oxidase, and Fe(III) underwent lipid peroxidation, as indicated by the thiobarbituric acid reaction and iodometric determination of hydroperoxides. In detergent-free medium (phosphate buffered saline) peroxidation was inhibited by superoxide dismutase, catalase, and EDTA; but was promoted by OH. scavangers, eg. mannitol. Generation of OH. in the system via iron-catalyzed reduction of H2O2 by O-2 was demonstrated by EPR spectrometry using spin trapping. In membranes treated with Triton X-100 lipid peroxidation was stimulated by EDTA and suppressed by OH. traps. This and other evidence suggests that OH. in the medium was an effective initiator of lipid peroxidation in detergent-dispersed membranes, but not in intact membranes.