Activity of free radical scavenging enzymes in red cells and plasma of patients undergoing extracorporeal low-density lipoprotein apheresis.

There is evidence that reactive oxygen species (ROSs) are generated in extracorporeal circuits. Free radical scavenging enzymes (FRSEs) such as glutathione reductase (GSSG-R), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) protect against the damaging effect of ROSs. The influence of extracorporeal treatment on FRSE activity was investigated in the plasma and red blood cells (RBCs) of 21 patients undergoing regular low-density lipoprotein (LDL) apheresis. The FRSEs GSSG-R, GSH-Px, and SOD were measured. Determinations were made before and after a single treatment. Because all apheresis patients suffered from coronary heart disease (CHD), 201 CHD patients and 90 individuals without CHD, neither group undergoing apheresis, served as controls. In apheresis patients, GSH-Px (33.9+/-8.2 U/g Hb) and GSSG-R (7.6+/-0.9 U/g Hb) activities were increased whereas SOD activity (5.4+/-1.5 U/g Hb) was decreased in RBCs before a single treatment compared to controls. Plasma FRSEs of apheresis patients were not different from those of controls. There was no effect of a single treatment on FRSEs in RBCs. However, a significant decrease in plasma GSH-Px activity (209.9+/-24.9 U/ml) due to the extracorporeal treatment was observed. These data show that long-term extracorporeal therapy with LDL apheresis modulates the activity of antioxidant enzymes in RBCs whereas a single treatment was without major effect on FRSE activity in RBCs and plasma, except for plasma GSH-Px.