Stimulates glycogenolysis in the liver. Impairs glucose uptake by muscle and fat cells. Glucagon is secreted from the alpha cells of the pancreas as a result of hypoglycemia. Addison s disease results from a deficiency of epinephrine. Insulin increases cyclic AMP levels in the liver to activate glycogen synthase.
Glucagon stimulates the activity of the pyruvate dehydrogenase complex.
Insulin exerts most of its actions by a cyclic AMP second messenger mechanism. Insulin causes GLUT-4 transporters to increase at the surface of muscle cells. Insulin increases the activity of glycogen phosphorylase. Addison s disease. Cushing s syndrome.