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[Effect of oxidative stress in patients with chronic renal failure].

BACKGROUND
Cardiovascular disease remains the single most common cause of excess morbidity and mortality in end-stage renal disease (ESRD) patients and the traditional risk factors can't explain the high incidence of these events. New "non-traditional" risk factors are analysed in uremic patients and the increased oxidative stress is postulated to be an important contributor to uremic cardiovascular risk.


METHODS
In order to evaluate the effects of the hemodialysis treatment, a complete oxidative stress study was performed in fifteen uremic patients. Representative antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), together with oxidized/reduced glutathione ratio (GSSG/GSH) and other oxidation indicators including malondialdehyde (MDA) and 8-oxo-2'-deoxyguanosine (8-oxo-dG), were analysed to assess oxidative stress status in normal control volunteers and in uremic patients treated with hemodialysis (HD). In the latter group blood samples were taken prior and after HD to evaluate the effect of the session of HD over the oxidative markers.


RESULTS
Low levels of antioxidant enzyme activities were observed in the uremic patients as compared with normal control subjects. HD treatment results in a significant recovery of these enzyme activities but remain lower as compared with control values. Levels of GSSG and GSH concentrations were increased and reduced respectively in uremic patients. These differences were even higher before the HD and were reduced upon treatment to levels closer to those observed in controls. MDA levels and 8-oxo-dG levels were also increased in uremic patients with the highest values observed in the pre-treated HD group. Even though HD treatment decreases the levels of oxidation products in mononuclear cells of uremic patients the values of the control group are not reached.


CONCLUSIONS
Our results suggest that hemodialysis by itself could correct the oxidative status in these patients. The possible mechanisms involved in the oxidative stress changes with the hemodialysis treatment will be discussed below.