Mechanisms involved in alpha-adrenergic effects of catecholamines on liver metabolism.

Recent results have indicated that alpha-adrenergic receptors are the major mediators of catecholamine actions on liver metabolism in several species. It is well-established that cAMP and cAMP-dependent protein kinase are not involved in hepatic alpha-adrenergic effects. This review presents evidence that alpha-adrenergic stimulation of glycogenolysis in rat liver involves the mobilization of Ca2+ ions from mitochondria and stimulation of phosphorylase kinase by the resulting increase in cytosolic Ca2+ concentration. Possible mechanisms by which activation of alpha-adrenergic receptors causes release of mitochondrial Ca2+ and affects other cell processes are discussed.