Effect of intermittent hypobaric hypoxia on HIF-1 expression and morphofunctional changes in the myocardium

The main study objective is to evaluate the expression of Hif-1α, free radical oxidation activity and morphofunctional changes in the myocardium at different adaptation stages to intermittent hypobaric hypoxia. Materials and Methods. The study was conducted on 96 male Wistar rats. Intermittent hypoxia (IH) was reproduced in an altitude chamber (330 mm Hg) according to the following scheme: 5 min - decrease in Pb, 10 min - hypobaria, 5 min - increase in Pb, 5 min - normoxia. Rats underwent 3 hypobaric cycles daily, 6 days a week, for 30 days. IH was associated with the expression of Hif-1α in the myocardium (PCR), activity of malondialdehyde, superoxide dismutase, catalase and glutathione-S-transferase (spectrophotometry). Morphometry of capillaries and myocardial fibers was conducted on histologic specimen after injecting a postmortem contrast material into the bloodstream (light microscopy). Results. It was established that arterial hypoxemia arises during IH (PaO2 - 52.0-57.5 mm/Hg). It appeared in association with mixed metabolic and respiratory acidosis (1st day) and compensated respiratory alkalosis (15-30 day). During IH the accumulation of Hif-1α in the myocardium increases by 11.6, 6.4 and 2.7 times on the 1st, 15th and 30th day of adaptation. During 1-15 days of IH lipid peroxidation (LPO) is activated (MDA increases). The activity of catalase and glutathione-S-transferase is also increased. During the next 30 days LPO activity decreases, while the activity of antioxidant defense enzymes (SOD, MDA, glutathione-S-transferase) increase. Adaptation to IH leads to an increase in the total number of capillaries per unit of the myocardium surface (14.0 and 19.8 %) on the 15th and 30th day of the study.