Relative Potency of Glucagon and Epinephrine as Hepatic Glycogenolytic Agents: Studies with the Isolated Perfused Rat Liver

Glucagon induced slight glycogenolysis in the isolated perfused rat liver at concentrations of 0.4 μg/liter of plasma and substantial effects at moderately higher concentrations. These levels are comparable to those resulting from endogenous secretion of this hormone. In contrast, the minimal glycogenolytic concentration of epinephrine was about 140 μg/liter of plasma, far higher than any levels known to occur naturally in mammalian species. It is concluded that glucagon is a physiologic hepatic glycogenolytic agent, while the direct contribution of epinephrine to hyperglycemia is limited to its peripheral effects. (Endocrinology74: 930, 1964)