Superoxide Dismutase and Glutathione Peroxidase in Hemodialyzed Patients and Renal Transplant Recipients and Their Relationship to Osmotic Fragility

Increased oxidative damage is one of the most common complications in patients suffering from chronic renal failure (CRF), undergoing hemodialysis, which leads to various abnormalities including anemia. The study was designed in order to evaluate the changes in activities of two intracellular antioxidant enzymes; superoxide dismutase (SOD) and Glutathione peroxidase (GPX); in patients with CRF under regular hemodialysis and renal transplant recipients. Relationship between the enzymes activities and altered osmotic fragility of red blood cells, one of the minor causes of anemia, was also determined in these subjects.
The activities of SOD and GPX were measured by spectrophotometric methods in red blood cells of 40 hemodialyzed patients and 26 renal transplant recipients with mean age of 42.5 ± 14 years and 38.6 ± 10 years respectively. The results were compared with those obtained from 39 age and sex matched apparently healthy individuals with mean age of 39.9 ± 15.5 years as controls. Median osmotic fragility (MOF) of red blood cells was also determined colourimeterically in each group and its relationship to the enzyme activites was evaluated.
The activity of SOD in hemodialyzed patients (1080.5 ± 700.2 U/g Hb) was markedly lower than those of renal transplant recipients (1303.5 ± 442.2 U/g Hb) and the control group (1307.8 ± 452 U/g Hb) (p<0.05). The activity of GPX in hemodialyzed patients (23.9 ± 9.5 U/g Hb) was significantly lower than those of renal transplant recipient (28.1 ± 16.8 U/g Hb) and control group (34.6 ± 7.5 U/g Hb) (p<0.05). Although the activities of the both enzymes in the renal transplant recipients were higher than that of hemodialyzed patients but they were still lower than that of the control. Calculated values for MOF in hemodialyzed patients (0.46 ± 0.03) were significantly higher than those of renal recipients (0.42 ± 0.02) and control (0.41 ± 0.01) (p<0.05). In patients under hemodialysis significant correlations between SOD and MOF were observed (r = -0.3, p = 0.02).
As antioxidant measurement may help to delineate susceptibility to free radical attack, decreased activities of GPX and SOD in red blood cells of patients under hemodialysis may thus contribute to increased oxidative stress in hemodialyzed patients. Elevation of MOF in hemodialyzed patients and no correlation between MOF and the activity of GPX suggests that deficiency of SOD may be one of causes of elevated MOF. It seems that measurement of total antioxidant capacity will provide useful information in these patients.