RELATIONSHIP OF THE ADRENAL MEDULLA TO THE HYPERGLYCEMIC EFFECT OF GLUCAGON¹

Abstract

The effect of intravenously administered glucagon (0.4 mg./kg.) on the blood glucose level was studied in normal, adreno-demedullated and dihydroergotamine (DHE)-treated rats. Glucagon produced little or no change in blood sugar values among adreno-demedullated rats, in contrast to the distinct rise produced in normal animals. DHE treatment greatly diminished the hyperglyoemic response of normal animals to glucagon injection. The failure of glucagon to induce hyperglycemia in adreno-demedullated or DHE-treated rats was shown not to be due either to lack of initial glycogen stores or to failure of glucagon to induce hepatic glycogenolj'sis. In a replacement experiment, subcutaneously injected epinephrine (.05 mg./kg.) restored the hyperglycemic response of adreno-demedullated animals to glucagon. It is concluded that depression of the rate of peripheral glucose uptake by epinephrine action is a prerequisite for the hyperglycemic effect of glucagon, though not for its glycogenolytic action. Glucagon induced a small increase in muscle glycogen among adrenodemedullated animals but not in normal or DHE-treated animals.