NITRIC-OXIDE AS A FACTOR OF THE ANTIHYPOX IC EFFECT OF ADAPTATION TO EXERCISE

It is known that adaptation to exercise enhances the organism resistan ce to acute hypoxia. However the mechanism of this cross protective ef fect have been insufficiently studied. The analysis of literature sugg ests that NO may play a role in the development of the antihypoxic eff ect of adaptation to exercise. The aim of the present study was to tes t this hypothesis: first, by evaluating the influence of NO donor and NO-synthase inhibitor on the antihypoxic effect of adaptation to exerc ise and, second, by evaluating the changes of NO production in acute h ypoxia and after a course of adaptation to exercise. It was shown that the NO donor could both reproduce and considerably (three times) pote ntiate the antihypoxic effect of adaptation to exercise. At the same t ime, the NO-synthase inhibitor completely suppressed the development o f the protective antihypoxic effect of adaptation. After adaptation to exercise, the cerebral NO production was unchanged, while the hepatic NO production doubled. Acute hypoxia induced a biphase change in tiss ue NO production; initial increase (twofold in the brain) preceded a d ecrease (by 25% in liver and 37% in the brain as compared to the contr ol). Therefore, the increased NO production following adaptation to ex ercise can underlie the antihypoxic effect of such an adaptation.