Changes in Fatty Acid Metabolism after Erythrocyte Peroxidation: Stimulation of a Membrane Repair Process

Abstract

To study certain membrane repair processes in human erythrocytes, vitamin E-deficient cells were incubated with hydrogen peroxide. The incorporation of exogenous fatty acid and the transfer of fatty acid from phosphatidylcholine and neutral lipid into phosphatidylethanolamine were examined using radioactive fatty acids. Hydrogen peroxide stimulated the incorporation of fatty acid into all membrane phospholipids. The specific activity of phosphatidylethanolamine was increased disproportionately. The lipids of the membranes of erythrocytes were labeled with saturated and unsaturated fatty acid. When these erythrocytes were subsequently incubated with hydrogen peroxide, both types of fatty acid were transferred from superficial erythrocyte neutral lipids into phosphatidylethanolamine. However, the unsaturated fatty acids of phosphatidylethanolamine were subsequently altered by hydrogen peroxide, whereas the saturated fatty acids were not. The cumulative effect of these processes was a relative decrease in unsaturated fatty acid and an increase in saturated fatty acid in the phosphatidylethanolamine of the erythrocyte membrane. The net effect of these events represents the operation of repair processes which distort the usual fatty acid composition of erythrocyte membranes in the presence of H₂O₂. This distortion may contribute to membrane permeability changes which occur during peroxide exposure and which precede the eventual hemolysis of these cells.