One of the important characteristics of the formation of the cardiovascular system responses to physical activity are the features of the mechanisms of blood microcirculation (BM) regulation. However, the study of the microcirculation system reactivity in conditions of muscular activity requires a clear understanding of the mechanisms of rearrangements in all parts of the microvasculature. The inconsistency of data concerning changes in the density of functioning capillaries under the influence of physical exertion is noted. Depending on the load power either an increase in the density of functioning capillaries in active and inactive organs is observed, or a decrease of this index in inactive tissues. On the other hand, structural and functional rearrangements of the mitochondrial apparatus of cells in the body tissues accompany the formation of adaptive or pathological reactions in response to the development of hypoxic states of various geneses, including hypoxia of the load. These features and contradictions point to the need to study the various links of the microvasculature, the mechanisms of regulation of microcirculation, the morpho-functional state of the mitochondrial apparatus of cells and those changes that occur under the influence of physical training. The purpose of the research was to investigate the relationships between changes of blood microcirculation and the ultrastructure of capillaries and mitochondria in muscle in response to exercise in young people of varying degrees of fitness and in animals under the experimental conditions. Materials and methods. Experimental studies were carried out on adult male rats (Wistar) weighing 220-250 g (n = 10). The dosed physical training (DPT) was created by swimming of the animals (30 minutes, once daily, or once a day within 3 weeks) in heated to 30-32° C water at the height of water column of 80 cm. The consumption rate of O2 was 70-75% of the maximum. The control group included 10 intact animals. The preparation of the tissue samples of calf muscle for electron microscopic investigations was performed by the usual method. Viewing of ultrathin sections (40-60 nm thick) was carried out using an electron microscope TEM-125K (Ukraine). Morphometric assessment of mitochondria was carried out using the computer program Image Tool Version 3 (USA). The total number of functioning capillaries (FC) was determined according to the methodology, proposed by H. Hoppeler et al. (2001). To identify the characteristics of BM, men at the age of 21 were examined: 15 students and 15 sportsmen. The DPT was performed on a veloergometer and was selected individually – the O2 consumption rate was 70-75% of the maximum. The BM was evaluated using laser Doppler flowmetry (LDF) by LAKK-01 (Lazma, Russia). Analysis of LDF-grams was performed in accordance with the instruction for the apparatus. Results and discussion. It was found that lack of fitness and/or initially low microcirculation index (BMI) is accompanied by a decrease in the effectiveness of blood flow regulation in response to DPT, while initially high values of BMI in sportsman indicate the possibility of compensatory increase in blood flow efficiency in the microcirculation system at DPT due to predominance of active regulatory mechanisms. In the experiment with DPT the ultrastructural manifestations of muscle adaptation were revealed, including initial signs of primary angiogenesis, the activation of mitochondrial (MC) morphogenesis. The formation of such compensatory and adaptive changes aimed at providing adequate energy metabolism and preventing the development of secondary tissue hypoxia. Along with this, in the muscular tissue there were sites of hypertrophy of muscles, and sometimes an increase in the percentage of structurally damaged MC. Conclusions. Such wide range of changes in the morpho-functional state of the microvasculature can indicate individual features of the formation of adaptive mechanisms in the organism in response to DPT and explain the multidirectional changes in the microcirculation system.
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