In modern theoretical and practical biology and medicine, the key problem of research is to reveal the patterns of structural and functional organization of the human and animal body at different stages of development. Literature sources provide very limited data on the organization of the intermediate lobe of the adenohypophysis in humans, leaving insufficiently studied the ultrastructural state and activity of melanotropic cells of the intermediate lobe of the adenohypophysis in animals of different ages, including rats. The issues of the intermediate pituitary gland functioning remain important and little studied, especially in the period of the beginning of the optic-thalamic system. The purpose of the research was to study the ultrastructural changes of melanotropic cells of the intermediate lobe of the adenohypophysis in rats of different ages in the norm. Material and methods. In accordance with the purpose of the study we conducted the experiment on 30 nonlinear white male rats of different ages: 14-, 45- and 90-day-old. The animals were kept in the vivarium in equivalent conditions. The keeping and using of animals was carried out in accordance with the provisions of the "General Ethical Principles of Animal Experiments", approved by the IV National Congress of Bioethics. While examining the intermediate pituitary gland of intact rats on the electron microscope, the material was fixed in 2.5% solution of glutaraldehyde on phosphate buffer with fixation in 1% solution of osmium tetroxide according to Caulfield. It was dehydrated in alcohols of increasing concentration (70%, 80%, 90%, 100%) and acetone, poured into a mixture of epon-araldite. Semi-thin sections were made from the obtained blocks, which were stained with toluidine blue. Results and discussion. At the ultrastructural level in the intermediate lobe of the adenohypophysis of 14-day-old intact rats, several cell types could be identified that differed in the number and size of secretory granules. The ultrastructure of glandular cells of 45-day-old rats had no significant differences compared with 14-day-old animals. Secretory granules of different sizes and electron densities were observed in the cytoplasm of melanotropic cells. It was often possible to see a glandular cell with numerous secretory granules in one part of the cytoplasm, while in another they were virtually absent. Most melanotropocytes were characterized by slightly compacted mitochondria, but their numbers were slightly higher than in 45-day-old rats. The nuclei of most cells were large, oval in shape with a clear structure of nucleoli and their ribosomal component. The latter represented groups of ribosomes that were collected in osmophilic complexes. The amount of heterochromatin exceeded euchromatin and it was located mainly in the membrane with areas of rarefaction in the pore area Conclusion. In 14-day-old intact male rats, the intermediate lobe of the adenohypophysis was presented as a formed functionally active organ. In the ultrastructure of the cytoplasm of melanotropes there was a moderate development of organelles, and judging by the number and size of secretory granules, as well as the density of their content, we can assume that all these cells differed from each other in their functional activity. In 45-day-old intact rats, accumulation of secretory granules was observed in the cytoplasm of melanotropes, especially near the nucleus, which indicated an increase in melanocyte-stimulating hormones synthesis with age. The ultrastructural state of the cytoplasm and nucleus also indicated an increase in functional activity. The ultrastructure of the intermediate lobe cells of the adenohypophysis of rats at the age of 90 days differed from that of younger animals by signs of different functional activity of individual melanotropic cells
ULTRASTRUCTURAL CHANGES OF THYROTROPIC CELLS IN THE DYNAMICS OF EXPERIMENTAL IMMUNOSTIMULATION