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Quantitative characteristics of the myocardium and the cardiomyocytes during different stages of the postnatal development in Wistar rats

A. Iliev, G. Kotov, B. Landzhov, L. Jelev, I. Dimitrova, D. Hinova-Palova


Until recently there was a consensus that the growth of the heart during the foetal and postnatal development of the rat is primarily due to hyperplasia of the cardiomyocytes but at a certain moment during the early postnatal development of the heart, cardiomyocyte hyperplasia ceases and during the late postnatal period, heart growth occurs due to hypertrophy of the cardiac muscle cells. For this reason, in healthy rats, no significant changes in the number and size of cardiomyocytes are observed. The mean size of the cardiomyocytes increases in correlation with body growth during the postnatal development and these cells also possess the ability for additional hypertrophy in response to increased workload. While studying cell size, most authors measure the diameter of the cells in transverse histological slides by adopting a cylindrical model of the cell. The diameter is measured either directly in the individual cells or is determined indirectly.In the present study, the quantitative data on the morphology of the free wall of the left and right ventricle in Wistar rats have been obtained during the analysis of the hearts of 15 male rats, divided into five groups: two-week-old; one-month-old; three-month-old; six-month-old; twelve-month-old. For morphometric analysis we used five slides of the heart of each animal by randomly selecting zones in the material where there were no massive tears. The morphometric characteristics are presented and organized through schemes and diagrams, demonstrating the dynamics in the following quantitative indices: thickness of the free wall of the left and right ventricle (μm), transverse section of the cardiomyocytes (μm2) cardiomyocytic density (number of cells/mm2). The changes observed in these indices reflect a tendency for age-related hypertrophy. They are more dynamic and start earlier in the left ventricle and occur in a significantly smoother pattern in the right ventricle.

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About The Authors

A. Iliev

G. Kotov

B. Landzhov

L. Jelev

I. Dimitrova

D. Hinova-Palova

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