KINETICS OF THE PROCESSES OF GROWTH OF LINEAR SIZES AND NUMBERS OF CARDIOMYOCYTES IN THE MYOCARDIUM COMPLEX (LV + MZP) BEFORE AND AFTER THE RAT-BIRTH

• Main Authors: Zahoruiko G. E., Zahoruiko Yu. V., Shmulich A. V.
• Format: Article
• Language: English
• Published: Ukrainian Medical Stomatological Academy 2018-11-01
• Series: Вісник проблем біології і медицини
• Subjects: Wistar rats; ontogeny; heart; cardiomyocytes
• Online Access: https://vpbm.com.ua/upload/2018-4/10-min.pdf

Wistar rats were used: 15-16 and 20-21 diurnal embryos, newborns, 2.5 and 5, 7.5 and 10, 15, 20, 25, 30, 35, 40 and 45 day-old rats. From compact and trabecular layers of the myocardium of rats of different ages, ultrafine sections were prepared. In a series of negatives (6x9) cm2 obtained at 2000, Vv (in%) of dark (d) and light (l) CMCs was determined in the parenchyma (LV + MZP). At the location of the nucleus, a smaller diameter (d, ?m) of CMC images was measured. According to the formula: Vcmc = V (?m3) 100% / Vv (%) determined the volumes of CMC (?m3). Here Vn is the volume of the nucleus (?m3), and Vv is the relative volume of the CMC core (%). The number of CMCs in the parenchyma (LV+MZP) was determined by the formula: Nmc = mpar / ? Vcmc. Here mpar is the parenchyma mass (mg), ? = 1.05 g / cm3 = 1.05 mg / 109 ?m3 is the average value of myocardial density, Vcmc is the CMC volume (?m3). It was found that in the process of embryogenesis, the content of moderately dehydrated d-CMC increases in the parenchyma of the myocardium, which are in a state of physiological rest. The highest value of Vv d-CMC is equal to 41%, it is determined in the parenchyma of the trabecular myocardium of newborns. In the process of postnatal development of rats (1-7.5) days, activation of the contractile function of reserve resting d-CMC occurs, the relative volume of which decreases from 41% to 0%. Vv dual-core CMC in the parenchyma of the myocardium increases from 5% in newborns to 100% by 15 days after the birth of the rat. In the process of ontogenesis (15 days before birth and 45 days after), a continuous increase in the linear dimensions of CMC in a compact and trabecular myocardium is observed. For hypertrophic CMC of a compact myocardium, characteristic growth of longitudinal dimensions, in trabecular myocardium - growth of transverse sizes of myocytes. By 20 days after the birth of the rat, the differences in the linear characteristics of CMC of the compact and trabecular myocardium are leveled. After the birth of the rat, the proliferation of CMC in the parenchyma (LV + MZP) gradually fades to 15 days. For this period of time the number of CMC increases 2.5 days, (from 0.724 to 1.56) x 107. After 15 days, Ncmc ?const. Consequently, the increase in the number of CMCs in the parenchyma myocardium complex (LV + MZP) is completed by 15 days after the birth of Wistar rats.