Influence of melatonin on the activity of main enzymes of cori cycle in skeletal muscles, heart, liver and kidneys of alloxan-induced diabetic rats

Introduction. Melatonin, a potent antioxidant agent, is essential for glucose homeostasis. The objective of the study was to determine the influence of melatonin on basal levels of glucose in blood, activities of glucose-6-phosphatase in kidney and liver, pyruvate kinase in muscles and heart, content of glycogen in muscles and heart of rats with alloxan-induced diabetes. Materials and methods. Diabetes was induced in male Wistar rats by single intraperitoneal injection of alloxan monohydrates (170 mg/kg). Four days after diabetes induction, rats were divided into diabetic and melatonin-diabetic groups (10 mg/kg «Sigma» USA, daily and intraperitoneal for 14 days starting from the 5th day). Results. Melatonin injections caused normalization of the elevated serum glucose level in diabetic group of rats compared with basal glucose level before treatment. The activity of pyruvate kinase in muscle and heart tissue of diabetic animals was 45% and 63% less than in control groups, respectively. Regarding kidney and liver of diabetic rats, the activity of glucose-6-phosphatase was increased in average by 148% compared with control value. The glycogen content in the heart and skeleton muscles of diabetic animals was reduced in average by 20% compared with the control. Melatonin restored all these indexes back to normal level. Conclusions. These findings suggested that melatonin restored the events in Cori cycle by possible activation of glycolysis in skeletal and heart muscles and normalization of gluconeogenesis in liver and kidneys.