LIGHT- AND ELECTRON-MICROSCOPIC CHARACTERISTICS OF CHANGES IN THETHYROID GLAND DURING CHRONIC HYPOXIA

Abstract

The investigation aims were to study the ultrastructural changes in the cellular and extracellular matrices of the thyroid gland in the norm and chronic hypoxia. Materials and methods: 40 male white rats were divided into a test and control group. Animals of the control (I) group (n=20) were not subjected to intervention, in the test group (n=20) a model of chronic hypoxia was created - the animals were kept in a special ventilation barochamber daily for 2 hours 5 times a week. Anatomical, histological, histochemical, electron microscopic and morphometric methods were used. Morphometric parameters were calculated by use of program Statistica 10 (StatSoft.Inc.) (statistical processing was performed using W — Wilcoxon test (paired samples) with the control group). Results: Pathomorphological picture of the thyroid gland of rats subjected to hypobaric hypoxia, on the 15th day of the study was characterized by the acceleration of adaptive processes in gland cells and the development of reparative regeneration. Small structural changes in thyrocytes observed on the 15th day of the experiment show that the gland cells are not completely restored, adaptive processes do not occur completely. The area (12.21±1.43) and the diameter (6.25±0.48) of the nuclei are relatively increased compared to the control group. Analysis of samples from the thyroid gland of animals adapted to chronic hypoxia on the 30th day of the study shows that the gland cells adapted to the new conditions and completely restored their normal structure and size. The morphometric parameters of the thyroid gland were relatively close to the norm (normal cell diameter (5.96±0.38) and the area of the nuclei (12.11±1.43)). Conclusion: The results of the studies showed that under the influence of prolonged hyperbaric hypoxia, the body's resistance to it, especially the thyroid gland, increases, and it adapts to hypoxic conditions, and this is accompanied by the processes of structural reorganization of organs. Thyrocytes of the thyroid gland adapt earlier to chronic hypoxia and respond to this by hyperplasia and hypertrophy and differentiation of thyrocytes.