Dynamics of nuclear-cytoplasmic relations in cardiomyocytes in the rat`s heart in the early postnatal period in normal conditions and experiment

Abstract

Dexamethasone is administered to pregnant women with high risk of preterm delivery, but his impact during intrauterine development can program progression of undifferentiated connective tissue dysplasia and a tendency to cardiovascular diseases in adulthood. The aim of the study was to determine the changes of the nuclear-cytoplasmic relations (NCR) of cardiomyocytes (CMC) in the myocardium in the postnatal period after intrauterine administration of dexamethasone. 144 hearts of laboratory rats were studied from 1 to 45 days of life, which were divided into 3 groups: first — intact group, animals of second group were injected by 0.05 ml dexamethasone solution on the 18th day of intrauterine development, and III — control group. Tissue sections were stained with hematoxylin and eosin. Statistical evaluation was carried out with Mann-Whitney U-test. p<0,05 was accepted as statistically significant. It has been found that, the NCR increases 1.56-fold from birth till 14-th day and decreases 2.55-fold till 45-th day in the myocardium of the left ventricle. There changes correspond for the transition from a proliferative to a hypertrophic growth, which occurs on 14-th day after birth in the heart of rodents. In animals of the experimental group, the NCR was significantly increased at 3, 5, 21, 30, and 45, but decreased on the 14-th day (p<0,01) in comparison with control group. The maximum value of the index was observed on the 5-th day, which indicates on early terminal differentiation of CMC in experimental animals. Thus, intrauterine administration of dexamethasone leads to early maturation of CMC, which reduces their number and may increase the risk of developing cardiovascular diseases in adulthood. In the future we plan to study the proliferative activity of CMC of rat`s heart in the postnatal period in normal conditions and after intrauterine administration of dexamethasone.