A Comparative Quantitative Analysis of the Postnatal Changes in the Myocardium of the Left and Right Ventricles in Rats

BACKGROUND: The growth of the heart during the foetal and early postnatal development takes places mainly due to hyperplasia. The late postnatal development is characterised by cardiomyocytic hypertrophy in response to normal physiological mechanisms and increased load. To study the cell size most authors measure the diameter either directly or indirectly. AIM: The aim of the present study was to make a comparative quantitative analysis of the postnatal changes observed in the left and right ventricles in rat by evaluating the changes in three morphometric parameters - thickness of the free wall, transverse section of the cardiomyocytes and cardiomyocytic density in the left ventricle and right ventricle. MATERIALS AND METHODS: In the present study, we used histological material from the hearts of 15 male Wistar rats, distributed in five groups aged 2 weeks, 1 month, 3 months, 6 months and 12 months, respectively. RESULTS: In both ventricles, the wall thickness and the transverse section of the cardiomyocytes increased with age, while the cardiomyocytic density decreased. Changes were identical in both ventricles; however, they were more dynamic and pronounced in the left ventricle. CONCLUSIONS: The studied morphometric parameters reveal that age-related hypertrophy and the gradual loss of cardiac muscle cells take place in both ventricles but have a more dynamic pattern of progression in the left ventricle as compared with the right ventricle.