AGE FEATURES OF STRUCTURAL COMPONENTS OF MASTICATORY MUSCLE IN IODINE DEFICIENCY

Sahan N. T., Zayats L. M., Antуmуs O. V., Dutchak V. M., Pituley A. V

MORPHOLOGY

Scentific article

The purpose of our study was to identify the peculiarities of structural organization of masticatory muscles in rats at the stages of postnatal ontogenesis and their morphofunctional features in experimentally induced iodine deficiency (ID). The object of our study was the masticatory muscle of 48 white outbred male rats. Groups of animals: Group І – intact ((n=24) 12 sexually-immature (3-month-old animals, weighing 120-150 g) and 12 mature animals (6-month-old rats, weighing 180-200 g); Group ІІ – experimental – under conditions of iodine deficiency ((n=24) 12 sexually-immature and 12 mature animals). The study involved the following investigation methods: simulation of ID; histological examination; histochemical study (SDG activity; submicroscopic examination; study of biochemical composition of blood; statistical analysis of morphometric and biochemical parameters). On the 60th day of investigation the biochemical blood count of sexually-immature and mature animals showed the decrease in the levels of thyroid hormones, while the TSH levels were increased, as compared to the norm, and made up: TSH – (0.17±0.02) µmol/ml (р<0.01), Т3 – (3.46±0.41) nmol/L (р<0.01), Т4 – (76.65±8.95) (р<0.01) nmol/L (sexually-immature animals); TSH – (0.12±0.01) µmol/ml (р<0.01), Т3 – (2.98±0.32) nmol/L (р<0.01), Т4 – (67.2 ±6.62) nmol/L (р<0.01) (sexually-mature animals). Histologically, muscle fibers of masticatory muscles of sexually-immature rats with iodine deficiency are characterized by irregular alternation of dark and light bands, enlarged nuclei. A significant amount of glycosaminoglycans is clearly identified in the ground substance of connective tissue. While studying the SDG activity of muscle fibers, we have observed a change in the distribution of different types of fibers. The number of muscle fibers with intermediate activity of succinate dehydrogenase has decreased (MF with IA of SDG) by 13.38%. At the same time the number of muscle fibers with low activity of succinate dehydrogenase has increased (MF with LA of SDG) by 99.81%. The number of muscle fibers with high activity of SDG (MF with HA of SDG) has remained almost unchanged and made up 16.04%. The diameter of the cross-section of muscle fibers increases, especially in the MF with LA of SDG. The ultrastructural study of muscle fibers of masticatory muscles of immature animals showed focal alteration of clear cross striation, cleared enlarged nuclei, cleared sarcoplasm, significantly enlarged and blurred Z-line, expanded structural components of the muscular triads. Mitochondria have low electron density matrix. The disintegration of mitochondrial crests is observed. Muscle fibers of mature animals with ID exhibit a marked cross-striation pattern, but there are areas with its destruction. Nuclei of muscle fibers are peripherally located and are visually enlarged. A slight increase in the crosssection diameter of all types of fibers is observed. Glycosaminoglycans were found in the ground substance of connective tissue. The study of SDG activity revealed a slight decrease in the number of MF with IA of SDG (by 6%) and a slight increase in the number of MF with LA of SDG (by 1.39%), as compared to the norm. The number of MF with HA of SDG remaines unchanged. Submicroscopic examination of mature animals with experimental ID has revealed a minor disturbance of the cross striation pattern of myofibrils in muscle fibers, some blurring and smoothness of Z-lines, enlargement and clarification of muscular triads. Large optically clear nuclei are observed in sarcoplasm and are located subsarcolemally. Rounded mitochondria with clear matrix and decomposed crests are visualized near the nuclei. The elements of the Golgi apparatus are expanded, forming vacuoles with light contents. Cisterns and tubules of granular endoplasmic reticulum are enlarged, with smooth surface. Multiple pinocytic vesicles appear in the sarcoplasm.

thyroid gland, iodine deficiency, muscle fiber, masticatory muscle. Р

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«Bulletin of problems biology and medicine» Issue 3 (157), 2020 year, 251-254 pages, index UDK 616.742+616-092.9+616.441-008.64

10.29254/2077-4214-2020-3-157-251-254