The effect of physical activity of varying intensity on cardiomyocyte hypertrophy and myocardial polyploidy in rats

Regular exercise improves cognitive function, reduces the risk of premature death from cardiovascular disease, stroke, diabetes and improves quality of life.Aim: To study the morphological parameters of cardiomyocytes of the left ventricle of the heart and the proliferative activity of rat cardiomyocytes during physical activity of different intensity.Methodology and Research Methods. Outbred male rats (n = 30) were taken as experimental animals and divided into three series. The first series of rats were given light physical activity - the animals swam in the bath for 15 minutes. The animals of the second series were in the bath for 30 minutes (moderate severity), the third series were in the bath until they began to lose strength and sink (in 55-59 minutes). Animals were taken out of the experiment after 10 sessions of water loading. Some rats (5 animals per series) were slaughtered 30 days after the end of the experiment. After extraction, the heart was stained with hematoxylin and eosin, the amount of DNA in the nuclei of cardiomyocytes was determined, binuclear and Ki-67 positive cells were counted, and the diameter of cardiomyocytes was measured. Statistical analysis was carried out in the program “Statistica 10.0”.Results. Histological examination revealed changes only in the myocardium of the left ventricle of rats of the third series: pronounced dystrophic changes in cardiomyocytes. There were cells with necrobiosis, focal necrosis of groups of cardiomyocytes. The highest level of cardiomyocyte polyploidy occurred in the second and third series (the ratio of diploid and tetraploid cardiomyocytes in the control corresponded to 91.6 ± 7.4%; 8.2±6.3%). In these series, there was also a change in the number of binuclear cells (in the control - 12.7 ± 1.9‰). In all series of Ki-67 positive nuclei were not detected.Conclusion. Severe physical activity leads to structural disorders of the myocardium, persistent hypertrophy of cardiomyocytes and is accompanied by a decrease in the proliferative activity of cardiomyocytes.