OXIDATIVE STRESS DURING DIALYSIS - EFFECT ON FREE-RADICAL SCAVENGING ENZYME (FRSE) ACTIVITIES AND GLUTATHIONE (GSH) CONCENTRATION IN GRANULOCYTES

Background. Living cells are protected by free radical scavenging enzy mes against oxygen radical-mediated damage. It has been suggested that granulocytes are activated on the surface of dialyser membranes, resu lting in the generation of free radicals. We have recently reported a lack of plasma lipid peroxidation and unchanged glutathione peroxidase (GSH-Px) as well as glutathione reductase (GSSG-R) activities in red blood cells of haemodialysis patients. However, because mature red cel ls are free of DNA and RNA, free radical scavenging enzymes (FRSE) can not be regulated on the gene level in response to an acute oxidative s tress. In contrast to erythrocytes, granulocytes are nucleated cells a nd FRSE protein concentrations can therefore be modulated. Methods, GS H-Px, GSSG-R, superoxide dismutase (SOD) activities and total glutathi one (GSH) were determined spectrophotometrically using a Cobas Fara se mi-automatic analyser in granulocytes of 31 healthy blood donors and i n 28 patients with chronic renal failure (CRF) for more than 6 months before as well as immediately after a single dialysis treatment. Patie nts were treated either by haemodialysis (n = 17) using low-flux polys ulphone membranes or by haemofiltration (n=11) usings high-flux polysu lphone membranes. Results. Compared to healthy controls, SOD and GSSG- R activities were increased in granulocytes of HD and HF patients, GSH and GSH-Px were decreased before a single treatment. After dialysis S OD and GSH-PX activities were significantly induced by both HD and HF whereas GSSG-R activities and GSH were decreased. Conclusions, These r esults show that the enzymatic defence against oxygen radicals can be induced in granulocytes of patients undergoing regular dialysis treatm ent: whereas the non-enzymatic defence is compromised as shown by decr eased GSH concentrations, both suggesting increased oxidative stress.