[The effect of hemodialysis on some parameters of the antioxidant system in the blood of patients with chronic renal failure].

UNLABELLED

Direct contact of the blood with the dialysis membrane during hemodialysis elicits a series of changes in blood cells. White blood cell count and total lymphocyte number are reduced, neutrocytes are stimulated and degranulate, platelet adhesiveness is enhanced. Interactions of granulocytes with the dialysis membrane stimulate the production of ROS and activate aerobic reactions triggering oxidative stress. Red blood cells form the "first line of defense" during contact of the blood with the dialysis membrane. The effect of ROS on erythrocytes appears in the form of reduced osmotic resistance of their cellular membrane and susceptibility to disintegration which results in the release of small quantities of hemoglobin and significant reduction in the lifetime of these cells. Oxidative stress caused by contact of the blood with the dialysis membrane triggers defense mechanisms in the erythrocyte that protect against oxidative damage. Reports on the effects of hemodialysis on the antioxidant system of the blood in patients with chronic renal failure are conflicting and the present work was aimed at resolving some of the discord. The following questions were addressed: (1) Does hemodialysis affect the antioxidant system of the blood in patients with chronic renal failure? (2) Are there associations between parameters of hemodialysis and of the blood's antioxidant system? (3) Is supplementation with antioxidants needed in hemodialysed patients? The experiments were done at the Department of Biochemistry and Chemistry, Pomeranian Medical University. Plasma and erythrocytes were obtained from 42 patients aged 67.7 +/- 12.3 years, treated at the Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, due to chronic renal failure caused by chronic glomerulonephritis (n=16), pyelonephritis (n=12), diabetes (n=3), arterial hypertension (n=3) or other cause (gout, nephrolithiasis, n=8). The patients were assigned to two equal groups: 1--with end-stage renal failure on hemodialysis; 2--eated conservatively. Hemodialysis was done three times per week, 4 hours per session, using Fresenius dialysers with polysulfone membranes and bicarbonate buffer with glucose. The control group comprised 21 healthy volunteers. All groups were matched for age and gender. A 10 mL heparinized blood sample was collected twice from group 1 patients before and after dialysis directly from the dialysis catheter and once after an overnight fast from group 2 patients and controls. Glutathione concentration was determined in whole blood. Plasma was prepared by centrifugation and MDA, Se, Cu, Zn, and Fe levels were measured. SOD, GSH-Px, and CAT activities, MDA, Se, Cu, Zn, and Fe levels were determined in erythrocytes. Statistical methods were applied to determine significance of differences between groups and correlations between parameters studied.

CONCLUSIONS

(1) Hemodialysis leads to significant changes in the antioxidant system of the blood of patients with chronic renal failure. The effect is noticeable with antioxidant enzyme activities and concentrations of nonenzymatic components of the system. (2) The activity of erythrocyte GSH-Px decreases with time of dialysis potentiating the effects of oxidative stress. (3) Reduced erythrocyte levels of Se in dialysed patients correlate with lower GSH-Px activities. Selenium supplementation may be of benefit to the antioxidative defense mechanisms.