Glutathione antioxidant system as a marker of oxidative stress in chronic renal failure

A profound imbalance between oxidants and antioxidants has been suggested in uremic patients on maintenance hemodialysis. However, the respective influence of uremia and dialysis procedure has not been evaluated. Circulating levels of copper-zinc superoxide dismutase (CuZn SOD), glutathione peroxidase (GSH-Px), and reductase (GSSG-Rd), total GSH and GSSG were determined in a large cohort of 233 uremic patients including 185 undialyzed patients with mild to severe chronic renal failure, and 48 patients treated by peritoneal dialysis or hemodialysis. Compared to controls, erythrocyte GSH-Px and GSSG-Rd activities were significantly increased at the mild stage of chronic uremia (p < .001), whereas erythrocyte CuZn SOD activity was unchanged, total level of GSH and plasma GSH-Px activity were significantly decreased, and GSSG level and GSSG-Rd activity were unchanged. Positive Spearman rank correlations were observed between creatinine clearance and plasma levels of GSH-Px (r = .65, p < .001), selenium (r = .47, p < .001), and GSH (r = .41, p < .001). Alterations in antioxidant systems gradually increased with the degree of renal failure, further rose in patients on peritoneal dialysis and culminated in hemodialysis patients in whom an almost complete abolishment of GSH-Px activity was observed. In conclusion, such disturbances in antioxidant systems that occur from the early stage of chronic uremia and are exacerbated by dialysis provide additional evidence for a resulting oxidative stress that could contribute to the development of accelerated atherosclerosis and other long-term complications in uremic patients.