Erythrocyte antioxidant defense system in patients with chronic renal failure according to the hemodialysis conditions.
BACKGROUND: Patients suffering from chronic renal failure (CRF) are exposed to increased oxidative stress generated by uremic toxins, factors connected with hemodialysis, chronic inflammatory state, lack of vitamins A, E and selenium, advanced age, and parenteral iron administration. Their antioxidative system is inefficient. In erythrocytes, hexosemonophosphate (HMP) cycle does not assure an adequate amount of reductive equivalents (NADPH) necessary to restore reduced glutathione (GSH), an important free radical scavenger. Hemodialysis treatment also causes a large loss of glucose, which is the basic substrate for that metabolic pathway. The object of the research was to establish the influence of glucose present in dialysate on antioxidant defense system in red blood cells. METHODS: A group of 51 patients undergoing regular hemodialysis using glucose (26 subjects, GL+ HD) or non-glucose fluid (25 subjects, GL- HD) was studied. The GSH concentration, glucose-6-phosphate dehydrogenase (G-6-P DH) and glutathione reductase (GSSG-R) activities were determined. Glucose concentration before and after the hemodialysis session was also measured. RESULTS: The activity of G-6-P DH was significantly higher in GL+ HD both before (p = 0.000) and after (p = 0.0002) the dialysis treatment compared to GL- HD, respectively, and to the healthy subjects (p = 0.000). The hemodialysis session caused a decrease in the activity of the enzyme in GL+ HD from 4.91 +/- 1.53 to 4.42 +/- 1.40 U/g Hb (p = 0.004) as well as in GL- HD from 3.97 +/- 1.00 to 3.59 +/- 0.87 U/g Hb (p = 0.007). The GSSG-R showed an increase in activity in CRF patients before HD (in GL+ HD to 2.57 +/- 0.76 and in GL- HD to 2.82 +/- 0.98 U/gHb). After dialysis, lower values were observed, particularly in GL+ HD (2.05 +/- 0.59 U/g Hb, p = 0.004). GSH concentrations in the examined group were higher (in GL+ HD 0.0205 +/- 0.008 and in GL- HD 0.0196 +/- 0.008 mmol/g Hb) than in controlled subjects (0.0142 +/- 0.002 mmol/g Hb) and decreased during dialysis treatment (considerably only in GL- HD to 0.0183 +/- 0.007 mmol/g Hb, p = 0.056). Glucose concentrations in GL+ HD were significantly higher compared to GL- HD (p < 0.002). CONCLUSIONS: Glucose presence in dialyzing fluid improves the HMP cycle activity as well as glutathione system reactions and determines a better antioxidant status of erythrocytes. It limits hemolysis and improves the hematological parameters in CRF.