AGE CHANGES OF SIZES AND NUMBERS OF CARDIOMYOCYTES, THEIR NECLEI IN THE PROCESS OF PRENATAL AND EARLY POSTNATAL DEVELOPMENT OF RATS HEART

Zagorujko G. E., Zagorujko Yu. V.

MORPHOLOGY

Scentific article

Most experiments on age morphology, biochemistry and physiology are carried out on laboratory animals, including Wistar rats of herd breeding. The life span of these animals does not exceed 2.5-3 years. White rats are used to study the mechanisms of ontogenesis and to search for experimental ways of prolonging life. In the work, were used rats of the Wistar line from the vivarium of the V.N. Karazin Kharkiv National University. Age of animals: 15-16 days and 20-21 days of embryogenesis, newborns, 5, 10, 15, 20, 25, 30, 35, 40, 45-day-old rats. When determining the age of embryos of rats, a zero day of pregnancy was considered the first day after mating the animals. The choice of this interval of ontogenesis is due to the fact that during this period the processes of differentiation, proliferation, maturation of CMC take place in the myocardium of rats. In each age group there were 5 individuals, mostly from the same group. When working with rats, we were guided by the European Convention for the Protection of Vertebrates used for experiments or for other scientific purposes (Strasbourg, 18.03.86). Ultrathin sections of the myocardium of the LV were examined and photographed with an increase in the electron microscope 2000х. For each age group of animals, 45-50 images of LV myocardium were photographed on a 6 x 9 cm film.To determine the relative volume of CMC nuclei (Vv% in%), a transparent test template measuring 6 x 9 cm was used, which contained system of points (No = 600). The template was combined with each analyzed negative. Morphometric analysis of a series of negative images of the myocardium of rats was carried out with the help of an optical mechanical installation “UMA-1”. Morphometric investigation of light-optical and electronic-microscopic images of cardiomyocytes (CMC) of left ventricle (LV) of Wistar line rats in the time interval of 15 days of prenatal – 45 days of postnatal development of animals was performed. In the embryonic myocardium of the LV, three groups of CMCs were identified. 1. Dark (d) moderately dehydrated t-CMC, the core of which has a volume equal to (90 ± 5.0) μm3. The number of d-CMC increases during the prenatal development of embryos and in newborns is 41%. 2. Light (l) actively functioning with l-CMCs contains a core with a volume of (151 ± 7.0) μm3. 3. A small amount of CMC (≈ 1%), which are in the S interphase period and contain a core with a volume of (181 ± 10.0) μm3. Within 15 days of postnatal development, 2-nuclear CMCs are formed from 1-nuclear CMC in the process of endomitosis, the number of which increases to 100%. Binuclear CMCs contain nuclei of different volumes. In the process of cardiomyogenesis, in the time interval of 5 to 45 days, the following variants of a consecutive combination of nuclei of different volumes are observed in 2-nuclear CMCs: (126 μm3 + 90 μm3) → (126 μm3 + 126 μm3) → (151 μm3 + 126 μm3) → (151 μm3 + 151 μm3) in 45 diurnal rats. From the moment of birth of the rats until the end of the maturation phase of CMC (45 days), the average CMC volume in the myocardium of the LV increases 14 times, from (880 ± 50) μm3 to (14050 ± 200) μm3. In the process of age-related hypertrophy of the myocardium of the LV, the nuclearcytoplasmic ratio (N: C) in CMC decreases from (1: 8.8) in newborns to (1: 45.5) in 45 diurnal rats.

cardiomyogenesis, cardiomyocytes (CMC), CMC volume, CMC nucleus volume, number of binucleare CMCs, nuclear – cytoplasmic ratio in CMC

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«Bulletin of problems biology and medicine» Issue 4 Part 3 (141), 2017 year, 304-311 pages, index UDK 612.172 : 611.127-018

10.29254/2077–4214–2017–4–3–141–304-311