[Change in the ultrastructure of rat myocardium under the influence of 12-months' adaptation to high altitude].

The right and left ventricle myocardium of rats was studied in the course of a 12-month period of adaptation to high altitude (3200 m above the sea level). A long-term exposure of the animals to the high altitude led the development of ventricular hypertrophy mostly of the right, and partly of the left ventricle. Hyperplasia and hypertrophy of individual organellae, particularly mitochondria, were found in most cardiomyocytes of both ventricles. In animals adapted to the high altitude the mitochondrial succinic dehydrogenase activity was more pronounced than in control ones. The results obtained testified to the enhanced intracellular metabolism reflecting myocardial compensatory adaptive responses.