According to modern data, the epiphyse (pineal gland) is an organ that combines the processes of adaptogenesis and immunogenesis, takes part in triggering stress reactions and determines the sequence of disorders in the body at different stages of stress development. Researchers consider the pineal gland to be the most important organizer of biological rhythms associated with photoperiodism and the organ that determines the stereotype of the organism. Its individual functions are rhythmically variable under the influence of the environment and age. The purpose of the study was to study the structural and functional changes of pineal cells of the pineal gland in rats at different stages of normal development, under the action of nitrates and the simultaneous action of nitrates and methylene blue. Materials and methods. In accordance with the purpose of the work, the study was carried out on 90 nonlinear white male rats of different ages. The animals were kept in the vivarium in equivalent conditions. Long-term exposure to nitrates on the body of animals was achieved by daily introduction into the drinking ration, starting from the 7th day of postnatal development of rats (after preliminary water purification), 120 mg/l sodium nitrate, that is, in a dose that is typical for many regions of Ukraine. When simulating the action of methylene blue, this substance was daily orally administered to the animals in doses: 0.1-0.15 ml of a 1% aqueous solution per 1 kg of body weight. Results and discussion. As a result of the 7-day action of nitrates in 14-day-old rats, structural changes were observed in the pineal gland, which corresponded to a decrease in the function of light cells and an increase in the functional activity of type II pinealocytes. The ultrastructure of the cytoplasm of type I pinealocytes contained poorly developed organelles and single secretory granules. In 45-day-old animals exposed to nitrates in light pinealocytes, pronounced disturbances in membrane organelles, primarily in mitochondria and the granular endoplasmic reticulum, were noted. The functional activity of dark pinealocytes increased during this period of the study. In the pineal parenchyma of 90-day-old rats after exposure to nitrates, the functional activity of type I pinealocytes was at a low level. The functional activity of dark pinealocytes was also weakened. Thus, as a result of the simultaneous action of nitrates and methylene blue in the pineal gland of 14-day-old rats, a tendency to gradual restoration of the structural and functional parameters of cells was observed. In 45-day-old animals, after the simultaneous action of nitrates and methylene blue, the ultrastructural data of pineal cells indicated numerous mitochondria and secretory granules in the cytoplasm. In the parenchyma of the pineal gland of 90-day-old rats after chronic action of nitrates and methylene blue at the ultrastructural level, no sharp changes in the cytoplasm and nucleus of light and dark pinealocytes were found in comparison with the control. Conclusion. The intake of nitrates in 14-day-old rats causes the development of a stress reaction, poorly developed organelles and signs of degranulation appear in the ultrastructure of light pinealocytes, however, the cytoplasm and nuclei of dark cells indicated an increase in function. In 45-day-old rats after exposure to nitrates, the signs of the stress reaction are enhanced. In the ultrastructure of the cytoplasm of light cells, pronounced violations of membrane organelles are determined. Enhanced function continues in dark pinealocytes. After the action of nitrates in 90-day-old rats, changes occur that are characteristic of the stage of depletion of the general adaptation syndrome, the result of which is a deep imbalance in the work of the pineal gland. The combined action of nitrates and methylene blue in 14-day-old animals helps to reduce the toxic effect and the strength of stress reactions in the pineal gland. In the ultrastructure of pinealocytes, the number of ribosomes, small secretory granules and mitochondria increases in comparison with the action of nitrates alone. In 45-day-old animals with the simultaneous intake of nitrates and methylene blue in the ultrastructure of melanotropic cells, the accumulation of secretory granules of the same size and electron density, an increase in the number of organelles and signs of restoration of the structure of the cytoplasm and nucleus are noted. The use of methylene blue against the background of long-term intake of nitrates in 90-day-old rats at the ultrastructural level of abrupt changes in the cytoplasm and nucleus of light and dark pinealocytes is not manifested in comparison with the control
Keywords: pineal cells, nitrates, pineal gland, methylene blue
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