GLYCOGEN CONTENT AND GLUCOSE-6-PHOSPHATASE ACTIVITY IN THE LIVER OF RATS WITH DEXAMETHASONE DIABETES UNDER CONDITIONS OF CHANGED PHOTOPERIOD AND ADMINISTRATION OF MELATONIN

Melatonin affects the functioning of the pancreas and is currently being considered as a potential means of correcting diabetic disorders. Melatonin deficiency can lead to impaired glucose tolerance, but the mechanisms of this hormone's influence on carbohydrate metabolism in diabetes have not yet been fully studied. Sexually mature 18-month-old purebred white male rats were divided into three groups: 1) control (intact rats), 2) rats with dexamethasone diabetes, which was induced by daily subcutaneous administration of dexamethasone solution (4 mg/kg, KRKA, Slovenia) for 13 days. at a dose of 125 mg/kg (according to O.V. Stefanov, 2001), 3) rats that were orally administered melatonin (Sigma, USA) at a dose of 10 mg/kg against the background of dexamethasone diabetes (Mok, J.X., et al., 2019). In each group of rats, three subgroups were distinguished: 1) rats that were kept under artificial equinoctial conditions during the experiment; rats kept under 24-hour lighting; rats kept in 24-hour darkness. Euthanasia of experimental animals was carried out by decapitation under light ether anesthesia on the 14th day from the beginning of the experiment in compliance with the norms of treatment of experimental animals. Glycogen content and glucose-6-phosphatase activity were determined in the liver of rats [KF 3.1.3.9]. Glycogen content in the liver of rats with dexamethasone diabetes was reduced by 11% (equinox); by 17% (24-hour light) and 15% (24-hour darkness) compared to equinox controls. At the same time, the content of glycogen in the liver of rats receiving melatonin against the background of diabetes did not differ from the indicators of intact animals at the equinox and under conditions of 24-hour light and 24-hour darkness. The activity of glucose-6-phosphatase in rats with dexamethasone diabetes was increased compared to the indicators of the control group under all conditions - on average by 64.5%. Enzyme activity in the liver of melatonin-treated diabetic rats was, on average, 2-fold lower than in dexamethasone-diabetic rats that did not receive any correction agents, but these values were likely different from those of control animals. Key words: melatonin, dexamethasone diabetes, rats, glycogen, glucose-6-phosphatase.