No abstract

Hydrogen peroxide (H2O2) could induce oxidative damage at long distance from its generation site and it is also an important signalling molecule that induces some genes related to oxidative stress. Our objective was to study the plasma and blood cells capability to detoxify H2O2 after intense exercise and its correlation with oxidative damage. Blood samples were taken from nine professional cycling, participating in a mountain stage, under basal conditions and 3 h after the competition. Catalase and glutathione peroxidase activities decreased (40 and 50% respectively) in neutrophils after the cycling stage, while glutathione peroxidase increased (87%) in lymphocytes. Catalase protein levels and catalase specific activity maintained basal values after the stage in plasma. Catalase protein levels decreased (48%) in neutrophils and its specific activity increased up to plasma values after exercise. Myeloperoxidase (MPO) increased (39%) in neutrophils after the cycling stage. Exercise-induced hemolysis and lymphopenia inversely correlated with cellular markers of oxidative stress. Plasma malondialdehyde (MDA) directly correlated with neutrophil MPO activity and erythrocytes MDA. Intense exercise induces oxidative damage in blood cells as erythrocytes and lymphocytes, but not in neutrophils.

We determined the effects of dietary vitamin C supplementation on erythrocyte antioxidant enzymes and on plasma antioxidants during athletic competition and short-term recovery. Blood samples were taken from 16 volunteer endurance athletes, participating in a duathlon competition, under basal conditions and both immediately and 1 h after the competition. The results were analysed taking into account the individual vitamin C intake and the plasma levels. Athletes were assigned to either the vitamin C-supplemented or control groups ( n=8 each). The control group had normal plasma ascorbate levels, the supplemented group high levels as a result of the higher vitamin C intake. Uric acid and lactate dehydrogenase increased after the competition only in the control group. Plasma ascorbate decreased after short-term recovery in the supplemented group. Erythrocyte catalase activity increased after the competition in the supplemented group. Glutathione peroxidase activity (determined with cumene hydroperoxide as substrate) increased only in the control group after short-term recovery. This pattern may suggest an important role for plasma ascorbate, and dietary vitamin C supplementation, in the defence against oxidative stress induced by exercise and in avoiding negative effects on erythrocyte integrity.