Evidence for membrane lipid peroxidation during the in vivo aging of human erythrocytes.

This study has examined the occurrence of lipid peroxidation in in vivo aged human erythrocyte membranes. Erythrocytes of various ages were separated on discontinuous stractan density gradients. Three erythrocyte fractions were analyzed: (I) Light--erythrocytes staying between stractan densities 1.053 and 1.043 g/ml, (II) predensest--erythrocytes staying between stractan densities 1.081 and 1.111, and (III) densest--erythrocytes passing stractan density 1.111. Peroxidative lipid damage of erythrocytes was assessed by measuring lipid extract fluorescence, by lipid thin-layer chromatography for the presence of adduct of phosphatidylserine (PS), phosphatidylethanolamine (PE) and malondialdehyde, and by thiobarbituric acid-reactivity. Fractions I, II and III contained, respectively, 0.2 +/- 0.1 (S.E.), 1.1 +/- 0.1 and 1.5 +/- 0.1 of phospholipid-malondialdehyde adduct (percent of total phospholipids), and relative lipid fluorescence 22.5 +/- 0.8, 29.3 +/- 0.5, and 33.4 +/- 0.8 per ml packed cells, respectively. Thiobarbituric acid-reactivity of erythrocytes in various fractions was similar. Untreated densest erythrocytes contained significantly reduced PS (12.9 +/- 0.5%), in contrast to light erythrocytes (16.1 +/- 0.1%) and increased PC (31.2 +/- 0.3 versus 27.8 +/- 0.8% of the total phospholipid). This study provides evidence for significant lipid peroxidative damage in the erythrocyte membrane during aging in vivo.