Changes in the Cellular Composition of the Rat Thymus 90 Days After Urethane Injection Against the Background of Selenium Intake

The aim of the study is to assess the cellular composition of rat thymus when isolated administration of selenium, urethane and combined exposure to two factors. Material and methods. The study was performed on 34 male Wistar rats, which were divided into 4 groups: 1 – intact, 2 – rats, which received selenium only for 1 month, 3 – animals, which were injected once intraperitoneal urethane, 4 – rats with combined selenium and urethane action. Histological preparations of the thymus were prepared according to generally accepted methods and further evaluated by the method of review microscopy, morphometry, immunohistochemical reactions, electron microscopy, statistical processing of data. Results. Ninety days after selenium, the rat thymus structure is slightly different from intact animals. The introduction of urethane leads to the development of excitation involution of the thymus, which is characterized by morphological changes, and manifests itself in a change in the shape of the organ lobes, in the expansion of the intercole gaps and in the fat tissue thereof, hyperplasia of the cortical substance of the thymus by increasing the number of mature lymphocytes, epithelial cells positive to pancytokeratin. At the ultramicroscopic level, the thymus lymphocyte decreases its nuclear-cytoplasmic index, and increases the number of mitochondria that have a light matrix with a small amount of crystal. Apoptotic bodies and a large number of electron-transparent vacuoles are visualized. When combined, the thymus structure differs from the intact group by an enlarged brain substance, but the number of epithelial cells that are positive to pancytokeratin and Ki67+-cells, as well as cells that express apoptosisregulating protein, decreases. Electron microscopy also indicates a large amount of mitochondria, but with welldefined crystals, when combined with selenium and urethane. There are a small number of electron-transparent vacuoles. Conclusion. The obtained data make it possible to draw a conclusion about the positive influence of the exchange rate of selenium on the T-cell link of immunity, at least for this period of study. In the course of the experiment, it was found that, against the background of the development of the adenoma of the lung caused by the introduction of urethane, at the stage of alveolar epithelium dysplasia signs of excitant thymus involution were detected. When selenium and urethane are combined, less pronounced changes are observed in the examined organ than in the isolated administration of urethane.