Role of plasma protein and low-molecular weight substances in the change of hydroxyl radical scavenging activity in hemodialysis patients

While it is well known that hemodialysis (HD) patients with end stage renal failure are exposed to high oxidative stress, there is not a general opinion regarding whether antioxidant activity is high or low in these patients. We evaluated the variation of plasma hydroxyl radical scavenging activity (p-HRSA) by a single-session of HD in 69 patients by using a new system, reactive flow-injection electron spin resonance. And then comparing p-HRSA with their biochemical parameters, we tried to elucidate what components affected p-HRSA in the HD patients. The average of p-HRSA significantly increased after HD and the variation of p-HRSA by HD was correlated with that of plasma total protein (TP). In 5 patients however, their p-HRSA decreased after HD, in spite of increasing TP. In pre-HD, the p-HRSA values and hydroxyl radical scavenging activity of low-molecular weight fraction of plasma were significantly higher in these 5 patients than in patients whose p-HRSA increased after HD. These 5 patients were in an inflammatory state. These findings suggest that p-HRSA is mainly affected by TP, but caution should be exercised in patients who have high p-HRSA before HD and whose p-HRSA does not increase after HD.