Morphofunctional status of cardio-vascular system of rats with arterial hypertension

The aim: Was to clarify the general patterns of structural changes in the left ventricular myocardial capillaries in rats with spontaneous arterial hypertension.

Materials and methods: Experiments were conducted on 50 ISIAH (inherited stress-induced arterial hypertension) line rats with arterial hypertension: juvenile young (45-day) and sexually mature (100-day) rats, as well as intact animals of the corresponding age. While extracted from the experiment rats of all experimental groups had their arterial pressure measured using a plethysmograph. Electron microscopic examination of the left ventricular myocardium and morphometric study of volumetric and quantitative densities, cross-section area, and form factor of micropinocytotic vesicles were conducted.

Results: In sexually mature rats with arterial hypertension, a high level of pressure is maintained. In 45-day-old rats with arterial hypertension in endothelial cells of myocardial blood capillaries there is a hyperactivation of biosynthetic processes (euchromatic nucleus, large-sized mitochondria, ER canals, Golgi complex), which may be a manifestation of reactive processes in response to a non-stable increase in arterial pressure. In the 100-day rats with arterial hypertension, the mosaic of the ultrastructure of the myocardium blood vessels is preserved, but destructively-dystrophic changes become more expressive and involve not only the organelles but also the integrity of the endothelial cell itself. Destructively-dystrophic processes in rat capillaries are accompanied by compensatory and adaptive ones. This is manifested by activation of the transport of substances, both transendothelial and paracellular, and quantitative density of micropinocytotic vesicles increases statistically significantly.

Conclusions: In myocardial capillaries of young (45-day) arterial hypertension rats, compensatory and adaptive changes are manifested by activation of biosynthetic processes in endothelial cells following a slight increase in micropinocytotic vesicles quantitative density and signs of destructive-dystrophic processes (minor edema and lysis of endothelial cell cytoplasm). In sexually mature (100-day) arterial hypertension rats in the blood capillaries of the myocardium, the destructive-degenerative changes increase is accompanied by preservation of signs of compensatory processes. Reducing the number of capillaries is offset by an increase in the number of micropinocytotic vesicles.