ROLE OF GLUCAGON IN MAINTENANCE OF EUGLYCEMIA IN FED AND FASTED RATS

The role of glucagon in the regulation of blood glucose in fed and fas ted anesthetized rats was studied by injecting intravenously 4 ml/kg o f a high-capacity (40 nmol/ml) high-affinity (0.6 x 10(11) mol/l) mono clonal glucagon antibody. Blood glucose was lowered by the antibody by 2 mmol/l in fed rats but remained unchanged in 10- and 48-h-fasted ra ts. Antibody injection significantly reduced plasma insulin in both fe d and 10-h-fasted rats. In 10-h-fasted rats, propranolol injection dec reased blood glucose by 0.6 mmol/l, and combined with antibody adminis tration, a decrease by 1.1 mmol/l was observed. Blood glucose was neve r < 3.3 mmol/l. Thus glucagon is partly responsible for maintenance of euglycemia in fed rats, whereas during fasting it plays a limited rol e. However, immunoneutralization of glucagon reduces insulin secretion irrespective of blood glucose. Additional mechanisms seem to be respo nsible for the maintenance of blood glucose in the fasting state when glucagon and the sympathoadrenergic system are blocked.