首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Ca2+ and K+ channels of normal human adrenal zona fasciculata cells: Properties and modulation by ACTH and AngII
Authors:John J Enyeart  Judith A Enyeart
Institution:Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210
Abstract:In whole cell patch clamp recordings, we found that normal human adrenal zona fasciculata (AZF) cells express voltage-gated, rapidly inactivating Ca2+ and K+ currents and a noninactivating, leak-type K+ current. Characterization of these currents with respect to voltage-dependent gating and kinetic properties, pharmacology, and modulation by the peptide hormones adrenocorticotropic hormone (ACTH) and AngII, in conjunction with Northern blot analysis, identified these channels as Cav3.2 (encoded by CACNA1H), Kv1.4 (KCNA4), and TREK-1 (KCNK2). In particular, the low voltage–activated, rapidly inactivating and slowly deactivating Ca2+ current (Cav3.2) was potently blocked by Ni2+ with an IC50 of 3 µM. The voltage-gated, rapidly inactivating K+ current (Kv1.4) was robustly expressed in nearly every cell, with a current density of 95.0 ± 7.2 pA/pF (n = 64). The noninactivating, outwardly rectifying K+ current (TREK-1) grew to a stable maximum over a period of minutes when recording at a holding potential of −80 mV. This noninactivating K+ current was markedly activated by cinnamyl 1-3,4-dihydroxy-α-cyanocinnamate (CDC) and arachidonic acid (AA) and inhibited almost completely by forskolin, properties which are specific to TREK-1 among the K2P family of K+ channels. The activation of TREK-1 by AA and inhibition by forskolin were closely linked to membrane hyperpolarization and depolarization, respectively. ACTH and AngII selectively inhibited the noninactivating K+ current in human AZF cells at concentrations that stimulated cortisol secretion. Accordingly, mibefradil and CDC at concentrations that, respectively, blocked Cav3.2 and activated TREK-1, each inhibited both ACTH- and AngII-stimulated cortisol secretion. These results characterize the major Ca2+ and K+ channels expressed by normal human AZF cells and identify TREK-1 as the primary leak-type channel involved in establishing the membrane potential. These findings also suggest a model for cortisol secretion in human AZF cells wherein ACTH and AngII receptor activation is coupled to membrane depolarization and the activation of Cav3.2 channels through inhibition of hTREK-1.
Keywords:
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号