Oxidative stress: the effect of erythropoietin and the dialysis membrane

Dialysis patients run the risk of impaired antioxidative defense and increased free radicals (FR) production. The study was made in order to compare FR-related parameters in ten patients treated with erythropoietin (EPO+) and ten patients not subject to this treatment (EPO-). All patients showed stable hemoglobin levels at > 95 g/L. FR-related parameters were monitored during hemodialysis (HD) using a polysulfon (PS) or a hemophan (H) membrane for 12 of them (6 EPO+ a 6 EPO-). The EPO- group was found to have a higher activity of superoxide dismutase (SOD, 1160 + 218 vs; 882 + 125 IU/gHb, p<0.01) and a higher SOD/glutathione peroxidase (GSHPx) ratio compared with EPO+ (30.5 +/- 7.1 vs; 21.2 + 4.8, p<0.01). A total of 35 healthy volunteers were also examined. When compared with controls EPO- showed higher SOD (p<0.001), lower GSHPx (p<0.05) and a higher SOD/GSHPx ratio (p<0.001). Thiobarbituric acid reacting substances in EPO+ and EPO- were comparable with the levels found in controls. HD using H as well as PS membranes was associated with a decrease in erythrocyte glutathione levels (GSH after 30 minutes; also for H after HD). HD using H and PS membranes resulted in a decrease in the plasma antioxidant capacity (AOC). We can conclude that the intraerythrocyte antioxidant conditions of EPO+ patients are similar to those found in the general population and differ from those in EPO- exhibiting increased SOD and the SOD/GSHPx ratio. HD using the H as well as the PS membrane is accompanied by oxidative stress.