A proposal for the mechanism by which α-adrenergic agonists, vasopressin, angiotensin and cyclic AMP induce calcium release from intracellular stores in the liver cell: A possible role for metabolites of arachidonic acid

An hypothesis, which seeks to explain the mechanisms by which α-adrenergic agonists, vasopressin and angiotensin induce the release of calcium from intracellular stores in the liver is presented. It is proposed that (a) the stimulation by one of these agonists of the hydrolysis of phosphatidylinositol located in the liver cell plasma membrane provides a source of arachidonic acid and (b) one of the products of arachidonic acid metabolism is a calcium ionophore which catalyses the release of calcium from intracellular stores, including the mitochondria, and an increased inflow of calcium to the cell. The experimental evidence (currently available in the literature) upon which the proposals are based is summarised. The possibility that an active metabolite of arachidonic acid may also mediate the cyclic AMP-induced release of calcium from mitochondria is discussed.