Effect of hypoxic preconditioning on free radical processes in tissues of rats with different resistance to hypoxia.

We studied the effect of single hypoxic preconditioning exposure (hypobaric hypoxia, 5000 m, 60 min) on free radical processes, glutathione system, and antioxidant defense enzymes in tissues of rats with different resistance to acute hypoxia. The intensity of free radical processes was shown to increase or decrease on day 1 after hypoxic preconditioning. These changes were tissue-specific and opposite in animals with genetically determined differences in the resistance to hypoxia. Hypoxic preconditioning contributes to the immediate resistance. The effect was more pronounced in low resistant animals, who did not exhibit signs of oxidative stress in tissues during the early posthypoxic period. By contrast, hypoxic preconditioning was followed by activation of free radical processes in tissues of highly resistant animals. These rats were characterized by low ability for the development of immediate resistance. Activation of free radical processes in the early period of adaptation (first hours after hypoxic preconditioning) does not play a role in the induction of immediate adaptive mechanisms for hypoxia.