Age-based changes in structure and functions of the spontaneously hypertensive rats’ heart

The paper provides a comparative characteristic of the heart structure and functions in normotensive (white outbred rats) as well as Spontaneously Hypertensive Rats (SHR) aged 9 and 24 months. When microscopically studying the morpho-functional components of the heart left ventricle of white outbred rats, the histological picture and morphometric study data in them correspond to the normal structure of all layers of the heart wall, regardless of selected age of the animals, that enables them to be considered as a normotensive control. When microscopically studying the left ventricle of the heart of the SHRs in both age groups, changes of an adaptive nature were detected (hypertrophy of cardiomyocytes, hyperplasia and hypertrophy of smooth muscle cells of the arterial vessel wall, etc.), dyscirculatory and destructive processes, indicating the ruinous effect of long-term arterial hypertension on the heart structure and functions. These parameters progress with age, as indicated by exhaustion of adaptive signs in the form of atrophy of part of cardiomyocytes and smooth muscle cells in the walls of arteries, development of arteriolar hyalinosis. Thus, the data of microscopic study of the heart left ventricle structural components and morphometric indices allow the determination of the destructive effect of chronic arterial hypertension on the morpho-functional features of the heart left ventricle in SHRs of different age groups. Comparison of morphometric parameters between the SHR9 and SHR24 groups shows that during the aging process in SHR, the number of cardiomyocytes and the area of their nuclei, the stromal-parenchymal ratio, percentage of vessels, connective tissue and endomysium significantly change. The findings show that stable compensated hypertrophy in SHR aged 9 months progresses to heart failure and exhaustion of adaptive processes in cardiovascular system with age.