Decreased Plasma Glutathione Peroxidase Activity in Uraemic Patients

Accessible online at: www.karger.com/journals/nef Dear Sir, We read with great interest the paper by Roxborough et al. [1] on the reduction of the glutathione peroxidase (GSH-Px) activity in haemodialysis (HD) patients. The authors noted that in serum of patients with endstage chronic renal failure (CRF), the GSHPx activity was 2.65 times lower when compared to controls (106 vs. 281 U/l; p ! 0.001). Following HD, the GSH-Px activity rose by 38%, although remained below control values. We studied some antioxidant parameters in blood of patients in different stages of CRF. Several groups of patients were investigated: nondialyzed patients and several groups of patients on long-term regular HD: (1) supplemented with baker’s yeast (placebo), (2) supplemented with selenium (Se) in the form of Se-rich yeast (Y-Se; 300 Ìg Se given orally three times a week), (3) treated with erythropoietin at doses of 2,000 U three times a week, and (4) supplemented with YSe and erythropoietin (doses as above). Blood samples were drawn into heparinized vacutainer tubes, and plasma was removed by centrifugation. The plasma Se concentration was assayed fluorometrically [2], and the plasma GSH-Px activity was measured spectrophotometrically by the method of Paglia and Valentine [3] with t-butyl hydroperoxide as substrate. The results obtained were compared with healthy subjects (control group). In all groups of patients, at the beginning of the study, the plasma GSH-Px activity was 1.8 to 2.1 times lower (p ! 0.001) as compared with the control group. The plasma Se levels in nondialyzed and in dialyzed patients before HD, taking the group together (n = 44), were significantly lower (p ! 0.001 and p ! 0.05, respectively) than in healthy subjects. The patients, methods of treatment and plasma Se levels, and plasma GSH-Px activities obtained are shown in table 1. In two groups of HD patients who were regularly supplied with Se, 3 months after supplementation the Se concentration in plasma increased significantly (p ! 0.001), but the GSH-Px activity did not