Enzyme Activities in Muscle and Liver After Destruction of the Ventromedial Hypothalamic Area and Administration of Insulin

Abstract

The activities of various enzymes and the glycogen content of skeletal muscle and liver were investigated in rats with hyperinsulinemia, induced by either ventromedial hypothalamic (VMH) lesion or administration of insulin. Three days after hypothalamic surgery the activities of hexokinase and lactate dehydrogenase were increased in muscle tissue. Three months postoperatively the hexokinase activity in muscle was normalized, while those of lactate dehydrogenase and glycerophosphate dehydrogenase were decreased. Daily administration of insulin for two months caused increasing activities of hexokinase, phosphofructokinase and lactate dehydrogenase in muscle. The glycogen content of the muscle was unchanged three days after the VMH lesion as well as after insulin administration. Three months post-operatively the muscle glycogen content was decreased. Qualitatively similar changes with lowered glycogen content and increased activities of glycolytic as well as hexose monophosphate shunt dehydrogenases were obtained in liver 3 months after VMH lesion as well as insulin administration. The results presented do not reveal any peripheral block in the glucose metabolism. This suggests no primary role of muscle tissue in the development of hyperinsulinemia.

Key words

Hyperinsulinemia - Hypothalamic Lesion - Insulin Administration - Enzyme Activities - Glycogen Content - Muscle - Liver