Decreased feeding and supraphysiological plasma levels of glucagon after glucagon injection in rats.

The effects of intraperitoneally injected pancreatic glucagon on feeding and on plasma levels of pancreatic glucagon as well as on blood glucose levels and liver glycogen content were investigated in rats, in order to test the physiological relevance of exogenous glucagon's satiety effect. The rats were intraperitoneally injected with various doses of glucagon [60, 240 or 480 micrograms/kg body weight (b.wt.)] or vehicle when they started to eat after a 12 hr period of food deprivation. Only the highest dose of pancreatic glucagon (480 micrograms/kg b.wt.) decreased the size and duration of the first meal after injection. Hepatic vein, hepatic portal vein and aortal plasma pancreatic glucagon levels were increased about 10 fold by 60 and 240 micrograms/kg b.wt. of glucagon and about 30 to 70 fold by 480 micrograms/kg b.wt. of glucagon. All glucagon doses reduced liver glycogen content and increased hepatic vein blood glucose levels similarly. The results indicate that decreased feeding after intraperitoneal injection of glucagon is a pharmacological effect of the hormone, at least under the conditions tested.