Hepatic adrenoceptors involved in the glycogenolytic response to exogenous (-)-norepinephrine in the dog liver in vivo.

Effects of various sympathomimetic amines on the hepatic glucose mobilization were studied in anesthetized dogs. Phenylephrine (30, 100, 300 micrograms), isoproterenol (0.1, 1, 10 micrograms) and (-)-norepinephrine (0.5, 5, 50 micrograms) were injected into the common hepatic artery in three separate groups of dogs. Dose-dependent increases in hepatic venous glucose concentration were observed following the injections of these drugs. Aortic glucose concentration also increased significantly, but to a lesser extent as compared with that in hepatic venous blood. Peak responses were obtained 3 to 5 min after the drug administrations. The increases in hepatic venous glucose concentration induced by the injections of (-)-norepinephrine were significantly diminished to a similar extent in dogs treated with either phentolamine (2 mg/kg, i.v.) or (-)-propranolol (0.2 mg/kg, i.v.). The results indicate that in the dog liver in vivo, both hepatic alpha- and beta-adrenoceptors can be involved in the hepatic glycogenolysis. The glycogenolytic response to exogenously administered (-)-norepinephrine is mediated via alpha- as well as beta-adrenoceptors in the liver of anesthetized dogs.