FEATURES OF MORPHO-FUNCTIONAL REARRANGEMENT OF THE HYPOTHALAMIC-NEUROHYPOFIZAR SYSTEM OF IMMATURE RATS IN THE EARLY STAGES OF DEVELOPMENT OF EXPERIMENTAL DIABETES MELLITUS

Zhurakivska O. Ya., Popovich Yu. I., Oliynyk I. U., Miskiv V. A., Zhurakivskiy V. M., Tymochuk O. V.

MORPHOLOGY

Scentific article

Oxytocin and vasopressin have a direct effect on pancreatic islets, which are excreted by the paraventricular (PN) and supraoptic (SN) nuclei of the hypothalamus. The literature describes two ways of activating the action of oxytocin on the A and B cells of pancreatic islets: the first mechanism is central – through interaction with the motoneurons of the nucleus of vagus nerve and peripheral – through vasopressin and oxytocin receptors on the A and B cells of the pancreas. Vasopressin affects V1v receptors of the A- and B-cells of the pancreas and leads through a cascade of mechanisms to the activation of insulin synthesis. Therefore, the purpose of our study was to establish morpho-functional changes of the hypothalamic-neurohypofizar system of one-month-old rats in streptozotocininduced diabetes mellitus (SDM). For research we used hypothalamus and neurohypophysis of 32 one-month old male rats of the Vistar line, which were divided into 2 groups: control (12 animals) and experimental (20 animals). Diabetes mellitus in the experimental group was modeled by intraperitoneal administration of streptozotocin (6 mg / 100 g body weight) previously diluted in 0.1 M citrate buffer pH 4.5. Control group of animals was injected intraperitoneally with citrate buffer in an equivalent dose. Material for research was taken on the 7th and 14th day from the beginning of experiment. We used biochemical, histological and electron microscopic research methods. Half-thin slices, 1 μm thick, were stained with a 1% solution of methylene blue. Histologic preparations and half-thin slices were studied under a microscope MS 300 (TLC) and photographed using the Digital Camera for microscope DCM 900. At 7-14 days of SDM glucose and glycosylated hemoglobin levels in the blood increase significantly, with insulin levels reduced by 2.6 times. Such biochemical changes are evidence of the development of a stable form of subcompensated diabetes mellitus. In the hypothalamic-neurohypophyseal system of immature animals at 7-14 days of SDM there is a stage of reactive changes, which is characterized by an increase in the functional activity of the neuroendocrine cells (NC) of the supraoptic and paraventricular nuclei of the hypothalamus. Morphologically, such changes are manifested: an increase in the area of nuclei of NC and nuclear-cytoplasmic index, hypertrophy and hyperplasia of the Golgi complex in light NC and increasing the volume density of neurosecretory granules (NG) in them, increasing the numerical density of dark NC. Such changes are accompanied by the restructuring of the hemato-encephalic barrier, followed by the establishment of direct contacts of hemocapillaries and NC. Under such condition in the neurohypophysis appears the nonmyelinated nerve fibers with light and dark axoplasma containing NG, synaptic vesicles, mitochondria, and neurofibrils. It can be assumed that the appearance of “light” and “dark” nonmyelinated nerve fibers is a specific reaction of the neurohypophysis to hyperglycemia. In terminals of axons, the volume density of NG decreases due to young and mature NG, while the volume density of diffusing and residual NG grows. There is an increase in the area of capillaries due to the increase in their lumen. At the same time, in the peripheral zone of endothelial cells, the number of fenestres and micropinocytotic vesicles increases. Such changes in neurohypophysis indicate an increased process of excretion of neurohormones in the blood. Conclusions. In the early stages of development of SDM, an increase in the functional activity of the hypothalamicneurohypophyseal system in response to hyperglycemia is observed.

supraoptic nucleus, paraventricular nucleus, neurohypophysis, streptozotocin-induced diabetes mellitus

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«Bulletin of problems biology and medicine» Issue 3 (145), 2018 year, 288-293 pages, index UDK 611.814.1+611.814.3+616.379-008.64

10.29254/2077-4214-2018-3-145-288-293