Many metabolic and morphological changes in tissues and others organs during the ischemic-reperfusion period are caused by free radicals produced in the ischemic area. All organisms are provided with antioxidative systems to protect themselves against the toxic effect of oxygen and its derivatives. The aim of our study was to determine the influence of exogenous antioxidants: mannitol and ascorbic acid as well as allopurinol - an inhibitor of xanthine oxidase, on the level of free radicals and antioxidative activity of enzymes in rat skeletal muscles during ischemia and reperfusion. The experiments were performed on male Wistar rats. Acute ischemia of the posterior limb was produced by placing a subcutaneous ligature on the thigh at the level of the inguinal ligament. At this stage of the experiment the animals were divided into 4 groups: A-the reperfusion group, B-group receiving allopurinol, C-group receiving mannitol, D-group receiving ascorbic acid. Samples of skeletal muscles were taken from the thigh before removing the ligature during the 3rd, 6th and 10th minute of reperfusion. We determined: the concentration of free oxygen radicals and the activity of superoxide dismutase, catalase and glutathione peroxidase. Treatment of rats subjected to ischemia-reperfusion with mannitol, allopurinol and ascorbic acid caused a decrease in the level of free radicals in ischemic skeletal muscles. Allopurinol proved to be an effective antioxidant which produced a statistically significant decrease in the level of free radicals. This may suggest that the inhibition of xanthine oxidase - a potential source of reactive oxygen forms after restoration of blood flow in acutely ischemic areas can reduce the effects of oxidative stress during the ischemic-reperfusion period.

Keywords: ischemia-reperfusion syndrome, Free Radicals, Xanthine Oxidase, Allopurinol, Ascorbic Acid, Mannitol