Exposure of human erythrocytes to oxygen radicals causes loss of deformability, increased osmotic fragility, lipid peroxidation and protein degradation.

The effects of two oxygen radical generating systems (H2O2 and ascorbate/Fe+2) on erythrocyte deformability, osmotic fragility, lipid peroxidation and protein degradation were studied. Incubation of erythrocytes with different concentrations of H202 (5-20 mM) or ascorbate/Fe+2 (10/0.1-40/0.4 mM) caused a loss of deformability and increased osmotic fragility. The loss of deformability has occurred in a dose-dependent fashion and was proportional to the extent of malonyldialdehyde (an indicator of lipid peroxidation) and alanine production (an indicator of protein degradation). Prior exposure of the erythrocytes to carbon monoxide (known to inhibit heme-protein degradation) prevented almost completely the loss in deformability caused by H2O2, indicating that the loss in deformability was due mainly to protein degradation rather than to lipid peroxidation. Erythrocytes incubated with either of the two systems have also shown morphologic changes characterized by a dose-dependent increase in echinocyte formation. The results indicate the importance of oxidatively damaged proteins in compromising the rheologic behaviour of the erythrocytes, particularly when the free radicals are involved.