A novel K+ current inhibited by adrenocorticotropic hormone and angiotensin II in adrenal cortical cells.

Adrenocorticotropic hormone (ACTH) and angiotensin II (AII) are peptides that regulate the production of steroid hormones by cells of the adrenal cortex. The cellular mechanisms linking these peptides to corticosteroid hormone secretion are not understood. In patch clamp recordings from bovine adrenal zona fasciculata (AZF) cells, we have identified a novel cholera toxin-sensitive K+ current (IAC), which is potently inhibited by both ACTH and AII with respective EC50 values of 4.5 and 145 pM. These two peptides depolarize AZF cells with a temporal pattern and potency that parallels the inhibition of IAC. With the discovery of IAC, we have identified a common molecular target for both ACTH and AII. The convergent inhibition of IAC by these two peptides suggests a mechanism whereby biochemical signals originating at the cell membrane can be transduced to depolarization-dependent Ca2+ entry and steroid hormone secretion.