The dissertation is aimed at studying the features of morphological changes and mechanisms of their regulation in the thyroid glands under the influence of adverse factors, namely the combination of salts of heavy metals. The regenerative capabilities of the glands in the abolition of pollutants have been studied separately. For a detailed study and analysis of the mechanism of action of heavy metals, a biological research design was formed, which included the use of 48 outbreed adult male rats. Animals were divided into 3 groups in order to study the combined effects of pollutants and in the recovery period after their abolition: 1- control group; 2- rats, which received a mixture of heavy metal salts (copper, zinc, iron, chromium, manganese and lead) with drinking water, which is inherent in the pollution of some regions of Ukraine, especially Sumy region. Group 3 - the recovery period, these rats received normal drinking water after canceling heavy metals.
In order to study the morphological features of the structure of the thyroid glands and their functional activity, the experimental animals were removed from the experiment on the 30th, 90th, 120th and 180th day.
With the help of a set of research methods: histological, morphometric, immunohistochemical, biochemical, enzyme-linked immunosorbent assay and statistical analysis of digital indicators, the solution of the goal was achieved.
During the study, we received data on changes in the linear parameters of the area of glands, cells and nuclei of parathyrocytes, the size of the stromal component and the density of cell distribution with excessive consumption of a combination of salts of heavy metals. Decomplexation and disorganization of epithelial trabeculae were observed in the parenchyma. In the stromal component appeared reactivated rearrangements, which were characterized by the growth of connective tissue. Also, more pronounced morphological changes were observed in the microcirculatory tract of the glands, namely the expansion of the lumen of small vessels, the phenomenon of stagnation. In parathyrocytes there was a development of hydropic dystrophy in two directions: edema and swelling. The nuclear-cytoplasmic index in the cells showed an increase of more than one unit during the whole observation period. Toxic effects of pollutants on the body of rats caused dysfunction of the thyroid gland, namely the suppression of parathyroid hormone secretion, its regulators and disruption of calcium homeostasis. The obtained results are confirmed by a significant statistical difference of indicators and the presence of correlation patterns between them.
For the first time the character of compensatory-adaptive processes and restoration of glands at cancellation of pollutants was studied and described, where a slight decrease in the intensity of structural modifications was observed and a change in cell composition in the parenchyma of the organ took place.
A set of immunohistochemical studies was used to clarify and supplement the information on the pathogenic effect of the combination of heavy metal salts and their relationship with the morphological features of the thyroid gland. It was found that throughout the experiment, proliferative activity was weakly positive, observed mainly in stem cells. The expression of heat shock proteins during the excess intake of heavy metal salts and during the recovery period was at a sufficient level, there was no decrease, and in some cases, there was even a tendency to increased synthesis in cells. This indicated signs of adaptation, partial compensation of pollutants on the body of experimental animals and activation of recovery processes. The application of immunohistochemical study of expression to the protein Chromogranin A allowed to study the secretory activity of parathyrocytes and to establish that the parenchyma is represented by cells with different functional activity.
According to the results of a comprehensive biological study was revealed morphological features of the parathyroid glands, both normally and during the entry of pollutants into the body. The results of linear morphometric parameters of glands and analysis of parameters of parathyroid hormone secretion and its modulators, as well as mechanisms of regulation of calcium homeostasis under combined exposure to heavy metal salts and in the recovery period indicate the dependence of these indicators on the duration of experimental studies.
The results of the dissertation research clarify and deepen the theoretical understanding of adaptation processes in the pancreas under the bad influence, and also serve as a basis for the use of these data in scientific and practical activities and educational process in training specialists of biology, medicine and veterinary medicine.
