Duality of the voltage-dependent calcium influx in adrenal glomerulosa cells

Both T- and L-type calcium channels are expressed in bovine adrenal glomeru losa cells and both channels are sensitive to moderate depolarizations of t he cell membrane induced by angiotensin II (AngII) or physiological concent rations of extracellular K+. These channels present distinct pharmacology, L-type channels being more sensitive to dihydropyridines, whereas T channel s are inhibited by lower concentrations of mibefradil, a new type of calciu m antagonist currently used for treating hypertension. The activity of thes e channels is also differently modulated by AngII, which inhibits T channel s through activation of protein kinase C and L channels through a Pertussis toxin-sensitive G protein. Finally, whereas the activity of L-type channel s is directly reflected on the levels of the cytosolic calcium concentratio n ([Ca2+](c)), T-type channels are more closely related to the control of s teroidogenesis, possibly through a kind of "calcium pipeline" linking the p lasma membrane to the mitochondria. In conclusion, two types of calcium channels, with distinct functions and d ifferential modulation by AngII, are activated by agonists of aldosterone b iosynthesis in adrenal glomerulosa cells. Most importantly, these channels have distinct sensitivities to currently used antihypertensive therapeutic drugs.