A NOVEL K-II IN ADRENAL-CORTICAL CELLS( CURRENT INHIBITED BY ADRENOCORTICOTROPIC HORMONE AND ANGIOTENSIN)

Adrenocorticotropic hormone (ACTH) and angiotensin II (AII) are peptid es that regulate the production of steroid hormones by cells of the ad renal cortex. The cellular mechanisms linking these peptides to cortic o-steroid hormone secretion are not understood. In patch clamp recordi ngs from bovine adrenal zona fasciculata (AZF) cells, we have identifi ed a novel cholera toxin-sensitive K+ current (I(AC)), which is potent ly inhibited by both ACTH and AII with respective EC50 values of 4.5 a nd 145 pM. These two peptides depolarize AZF cells with a temporal pat tern and potency that parallels the inhibition Of I(AC). With the disc overy Of I(AC), we have identified a common molecular target for both ACTH and AII. The convergent inhibition Of I(AC) by these two peptides suggests a mechanism whereby biochemical signals originating at the c ell membrane can be transduced to depolarization-dependent Ca2+ entry and steroid hormone secretion.