Stimulation of glycogenolysis and gluconeogenesis by epinephrine independent of its beta-adrenergic function in perfused rat liver

Abstract

A study was made of the relationship between the alpha and beta-adrenergic function and the stimulation of glycogenolysis and gluconeogenesis by catecholamines. Glycogenolysis was activated by epinephrine, norepinephrine and isoproterenol, with this decreasing order of potency. The activations of glycogenolysis by epinephrine and isoproterenol and of gluconeogenesis by epinephrine were not blocked by phentolamine, propranolol or both, despite complete blockade by propranolol of the epinephrine- and isoproterenol-induced increases in tissue cyclic AMP levels. Theophyllinc increased tissue cyclic AMP but was without effect on glycogenolysis and gluconeogenesis in either the normal or epinephrine-treated liver. These results not only are in accord with the view that the adrenergic receptor in the liver cannot be readily classified into an alpha- or a beta-receptor, but also suggest that intracellular cyclic AMP is not necessarily the only factor involved in the activation of glycogenolysis and gluconeogenesis by epinephrine in perfused rat liver.