HEPATIC GLYCOGEN AND BLOOD GLUCOSE CONTROL

The hyperglycaemic response to adrenaline and the hypoglycaemic response to insulin was measured in normal rats and in rats pretreated with either dihydroergotamine or propranolol under both fed and 24 hr starved conditions. Administration of propranolol to starved rats both impaired the hyperglycaemic response to adrenaline and increased sensitivity to the hypoglycaemic action of insulin. Although dihydroergotamine caused similar impairment of adrenaline hyperglycaemia in fed rats, there was no increase in insulin sensitivity. Potentiation of insulin hypoglycaemia may not be strictly related to blockade of adrenaline hyperglycaemia. Starvation for 24 hr caused over 95 per cent depletion of liver glycogen in the rat and over 99 per cent depletion in the rabbit. Despite this, there was no impairment of the hyperglycaemic response to adrenaline in the rat and the rabbit showed a good hyperglycaemic response to glucagon. An adequate glycaemic response to pharmacological doses of these drugs does not depend upon hepatic glycogenolysis. Propranolol neither impaired the hyperglycaemic response to adrenaline nor increased sensitivity to insulin in the fed rat. It may be that propranolol will potentiate insulin hypoglycaemia only in the absence of liver glycogen. © 1969.