title: Evidence for cAMP-independent bTREK-1 inhibition by ACTH and NPS-ACTH in adrenocortical cells.
abstract: Bovine adrenal zona fasciculata (AZF) cells express bTREK-1 K(+) channels that are inhibited by ACTH through cAMP-dependent pathways. In whole cell patch clamp recordings from AZF cells, we found that ACTH may also inhibit bTREK-1 by a cAMP-independent mechanism. When the potent adenylyl cyclase (AC) antagonist 2,5-dideoxyadenosine-3'-triphosphate (2,5-dd-3'-ATP) was applied intracellularly through the patch pipette, bTREK-1 inhibition by the AC activator forskolin was blocked. In contrast, bTREK-1 inhibition by ACTH was unaltered. The selective G(Sα) antagonist NF449 also failed to blunt bTREK-1 inhibition by ACTH. At concentrations that produce little measurable increase in cAMP in bovine AZF cells, the O-nitrophenyl, sulfenyl-derivative of ACTH (NPS-ACTH) also inhibited bTREK-1 almost completely. Accordingly, 2,5-dd-3'-ATP at concentrations more than 1000× its reported IC(50) did not block bTREK-1 inhibition by NPS-ACTH. These results indicate that ACTH and NPS-ACTH can inhibit native bTREK-1 K(+) channels in AZF cells by a mechanism that does not involve activation of AC.
authors.affiliation: Department of Neuroscience, The Ohio State University, College of Medicine and Public Health, Columbus, OH 43210-1239, USA. enyeart.1@osu.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Enyeart
authors.forename: Haiyan
authors.initials: H
authors.lastname: Liu
authors.forename: Judith A
authors.initials: JA
authors.lastname: Enyeart
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015383:Zona Fasciculata / Q000166:cytology*
chemical_list: C024813:ACTH, 2-nitrophenylsulfenyl-; D000067956:Adenylyl Cyclase Inhibitors; D024683:Potassium Channels, Tandem Pore Domain; C103742:potassium channel protein TREK-1; D005576:Colforsin; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP