Thiol levels, protein carbonylation and anaerobic sulfur metabolism in erythrocytes of peritoneal dialysis and predialysis patients

Aim: The goal of the present study was to investigate the changes in sulfur metabolism in erythrocytes of end-stage renal failure patients. Methods: The following substances were determined in erythrocytes of chronic kidney disease patients before dialysis, patients treated with continuous ambulatory peritoneal dialysis, and in a group of healthy volunteers: (i) sulfane sulfur level and activity of the enzymes involved in its metabolism and in cyanide detoxification; (ii) concentration of total and non-protein sulfhydryl groups -SH; and (iii) protein carbonylation rate. Results: Erythrocytes of chronic kidney disease patients in predialysis period contained lower levels of sulfane sulfur, non-protein thiols, total thiols and 3-mercaptopyruvate sulfotransferase. On the other hand, in erythrocytes of end-stage renal failure patients treated with continuous ambulatory peritoneal dialysis, sulfane sulfur, non-protein thiols, total thiols and 3-mercaptopyruvate sulfotransferase activity remained at the level observed in healthy controls. These changes indicate a disturbed thiol balance and anaerobic cysteine metabolism in non-dialysis patients, whereas continuous ambulatory peritoneal dialysis patients did not show these disorders. gamma-Cystathionase activity was equally elevated in predialysis period and in peritoneal dialysis patients, which means that chronic kidney disease pathology is accompanied by an increased expression of this enzymatic activity in erythrocytes. Erythrocytic rhodanese activity was unchanged and stayed at the control level in both groups. Protein carbonylation rate was equally enhanced in both patient groups, which indicated acceleration of oxidative processes and inability of continuous ambulatory peritoneal dialysis to correct these changes in erythrocytes. Conclusion: The CAPD as a replacement therapy helps to preserve thiol levels and anaerobic sulfur metabolism in erythrocytes.