Walsh K B, Wang C
Department of Pharmacology, University of South Carolina, School of Medicine, Columbia 29208, USA.
Cardiovasc Res. 1996 Aug;32(2):391-9. doi: 10.1016/0008-6363(96)00075-2.
The aim of this study was to determine the effects of Cl- channel blockers on the cardiac cystic fibrosis transmembrane conductance regulator (CFTR) Cl- current (ICl) and the protein kinase A-regulated L-type calcium current (PKA-ICa).
Whole-cell ICl and ICa were recorded from isolated guinea pig ventricular myocytes using the patch clamp technique during stimulation of PKA by forskolin (1 or 2 microM).
The inhibitory effects of clofibric acid, p-chlorophenoxy propionic acid, gemfibrozil, diphenylamine-2-carboxylate (DPC), anthracene-9-carboxylate, 4,4'dinitrostilbene-2,2'-disulfonic acid and indanyloxyacetic acid 94 were examined on the two currents. Clofibric acid (1 mM), p-chlorophenoxy propionic acid (1 mM) and gemfibrozil (250 microM) produced an approximate 50% decrease in ICl, but had no effect on the PKA-ICa. Surprisingly, application of DPC (500 microM and 1 mM) and anthracene-9-carboxylate (500 microM) strongly reduced both currents. However, inhibition of the Ca2+ and Cl- channels by DPC could be differentiated in two important ways. First, increasing the pH of the external solution from 7.4 to 10.0 prevented the block of ICl by DPC, but did not attenuate the reduction in the PKA-ICa. Second, DPC inhibited the PKA-ICa in mouse atrial myocytes which lacked ICl. Neither 4,4'dinitrostilbene-2,2'-disulfonic acid (100 microM) nor indanyloxyacetic acid 94 (50 microM) caused any change in either of the guinea pig ventricular currents.
Drugs such as DPC and anthracene-9-carboxylate which block the cardiac CFTR Cl- channel also inhibit the regulation of the L-type ICa. During beta-adrenergic stimulation, changes produced by these drugs on the cardiac action potential duration will be attributable to inhibition of both the Cl- and Ca2+ currents. Analogues of clofibric acid may serve as selective blockers of the CFTR Cl- channel that can be used to determine the physiological function of ICl in cardiac excitation.
本研究旨在确定氯离子通道阻滞剂对心脏囊性纤维化跨膜传导调节因子（CFTR）氯离子电流（ICl）以及蛋白激酶A调节的L型钙电流（PKA-ICa）的影响。
在使用毛喉素（1或2微摩尔）刺激蛋白激酶A的过程中，采用膜片钳技术从分离的豚鼠心室肌细胞记录全细胞ICl和ICa。
研究了氯贝酸、对氯苯氧基丙酸、吉非贝齐、二苯胺-2-羧酸盐（DPC）、蒽-9-羧酸盐、4,4'-二硝基芪-2,2'-二磺酸和茚满氧基乙酸94对这两种电流的抑制作用。氯贝酸（1毫摩尔）、对氯苯氧基丙酸（1毫摩尔）和吉非贝齐（250微摩尔）使ICl降低约50%，但对PKA-ICa无影响。令人惊讶的是，应用DPC（500微摩尔和1毫摩尔）和蒽-9-羧酸盐（500微摩尔）强烈降低了两种电流。然而，DPC对钙离子和氯离子通道的抑制作用在两个重要方面有所不同。首先，将细胞外溶液的pH从7.4提高到10.0可防止DPC对ICl的阻断，但不会减弱PKA-ICa的降低。其次，DPC在缺乏ICl的小鼠心房肌细胞中抑制PKA-ICa。4,4'-二硝基芪-2,2'-二磺酸（100微摩尔）和茚满氧基乙酸94（50微摩尔）均未引起豚鼠心室电流的任何变化。
诸如DPC和蒽-9-羧酸盐等阻断心脏CFTR氯离子通道的药物也会抑制L型钙电流的调节。在β-肾上腺素能刺激期间，这些药物对心脏动作电位持续时间产生的变化将归因于对氯离子和钙离子电流的抑制。氯贝酸类似物可作为CFTR氯离子通道的选择性阻滞剂，用于确定ICl在心脏兴奋中的生理功能。
