The question of the relationship between structure and function is extremely relevant and concerns both wild and inanimate nature, since it is often the structural organization of the object under study which determines its physicochemical properties, existence and functioning in specific conditions. The initial stage of adaptive reactions occurs immediately after the onset of any exposure. Such a statement is especially relevant for physical activity, when the oxygen demand of the body and, in parallel, oxygen debt, which can lead to the formation of load hypoxia, increases significantly. The variability of capillary blood flow is the background on which the adaptive reactions of the hemocirculation system as a whole unfold. The peculiarity of the functioning of microvessels, their high reactivity, the specifics of the organization, the high prevalence contribute to the fact that they are the most mobile link in the cardiovascular system. Modern histological and electron microscopic studies show that the morphofunctional transformations of the microcirculation system resulting from muscle activity are an important component in the mechanisms of adaptation of the organism. Therefore, changes in blood microcirculation may be due to morphofunctional remodeling of muscle tissue. However, the question of changes in blood microcirculation in normal and under dosed physical training and their relationship with ultrastructural rearrangements in tissues, cells and cell organelles remains to be insufficiently clarified. The purpose of the experimental research was the study of the correlation of capillary blood flow and some parameters of the muscle tissue ultrastructure depending on the training of the body. Material and methods. An experimental study of the response of body tissues to dosed physical activity was performed on the Wistar adult rats males weighing 220–250 g (n= 30). To study the immediate structural response of body tissues on dosed physical training (group 1, n= 10), the latter was created while swimming animals in warmed to 30–320C water for 30 min and the height of the water column when swimming 80 cm, which did not allow the animals to stand on their hind legs, under additional weight load, which was selected individually so that the rate of oxygen consumption was 70–75 % of VO2max. To determine the adaptive structural alterations in the tissues of the body we used a long (three–week) physical activity (group 2, n= 10), which was modeled by daily swimming by the rats in method similar to the 1st group of animals. The control group of animals consisted of 10 intact rats. Blood microcirculation was evaluated using laser Doppler flowmetry by LACK–01 apparatus (Russia) on animal tail. We determined the indicator of microcirculation characteristic of tissue blood flow per unit volume of tissue per unit time based on the analysis of the average flow of red blood cells; mean square deviation characterizing the temporal variability of blood microcirculation. Samples for electron microscopic studies were prepared using conventional methods with reagents from Sigma, USA and Fluka, Switzerland and examined using an electron microscope "TEM–125K" (Ukraine). The morphometric characteristics of mitochondria were determined using computer program Image Tool (USA) at 130–150 fields for each series of studies. The total number of functioning capillaries was determined according to the method of H. Hoppeler et al. at small (x 1600–2000) magnification of electron microscope. The statistical significance of the correlation coefficient r for a sample of n elements was determined by comparing the empirical (t) and critical (t *) values of the Student's t test (when t> t * r is considered statistically significant). The coefficients values ≤ 0.3 are the indicators of weak link or lack thereof; values> 0.4, but <0.7 – moderate metrics, and ≥ 0.7 – indicators of a high degree of communication between parameters. Results and discussion. The obtained results showed that in untrained rats, the dosed physical training caused the appearance of signs of hypertrophy and stratification of myofibrils in the calf muscle, the total number of mitochondria, their average diameter and area did not change significantly, but significantly increased the percentage of structurally modified mitochondria: 2.8 times in sub–sarcolemmal mitochondria and 2.1 times in the intra–miofibrillar mitochondria. The trained rats were found to have ultrastructural manifestations of muscle adaptation to exercise, which distinguished the changes from the effects of single dosed physical training. First, there were virtually no empty and burnt capillaries, and secondly, there was a significant increase in the number of functioning capillaries per unit area of tissue. Activation of mitochondria morphogenesis was established in the growth of organelles amounted to 72.8 % in sub–sarcolemmal mitochondria and 65.6 % in intra–miofibrillar mitochondria. There was also a moderate (up to 25–30 % of the average diameter of mitochondria in the muscle tissue of control rats) organ swelling and an increase in the percentage of structurally altered mitochondria. In untrained animals, there was an increase in muscle blood supply at low baseline values of microcirculation due to an increase in the number of functioning capillaries, about the same in trained and untrained animals (r=0.793). No correlation was found between the indicator of microcirculation and the number of mitochondria (r=0,095) and the number of structurally modified mitochondria (r=–0,296). This pattern was observed in the untrained rats of group I and II. At high output values of the indicator of microcirculation, the correlation of this parameter with the number of functioning capillaries is moderately negative (r=–0,616). Instead, a close positive correlation was found between the number of functioning capillaries and the root MSD in trained rats of this subgroup (r=0.914). In untrained animals, such a pattern was not revealed. Conclusion. There was also a close positive correlation between the number of functioning capillaries and mitochondria in muscle tissue (r=0.809), as well as a moderate negative correlation with the number of structurally modified mitochondria (r=–0.550).
Keywords: blood microcirculation, microcirculation index, dosed physical training, functioning capillaries, mitochondria
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