Effects of glucagon on amino acid metabolism in Japanese eels, Anguilla japonica

Abstract

Actions of glucagon were studied in eels with special reference to amino acid metabolism. A single injection of glucagon in doses of 50–500 μg/kg produced a marked hyperglycemia. The glycemic level was elevated immediately after the injection of glucagon (200 μg/kg) and returned to a normal value 12 hr after the injection. A single injection of glucagon at any dose level from 50 to 500 μg/kg produced no appreciable change in plasma amino nitrogen level. However, repeated injections of the hormone (500 μg/kg/4 hr) during a 12-hr period produced a statistically significant decrease in plasma amino nitrogen level. Repeated injections of glucagon also reduced plasma amino nitrogen level of previously alloxanized fish. Hepatectomy completely abolished the glucagon effect on plasma amino nitrogen in both intact and alloxanized fish. The levels of liver and muscle glycogen and the activities of liver glutamic oxaloacetic transaminase, liver glutamic pyruvic transaminase, liver fructose-1,6-diphosphatase, and liver phosphofructokinase were not affected by glucagon administration. From these results it is concluded that glucagon depressed plasma amino nitrogen level by stimulating hepatic amino acid incorporation from the plasma in eels.