Shieh C-C, Turner S C, Zhang X-F, Milicic I, Parihar A, Jinkerson T, Wilkins J, Buckner S A, Gopalakrishnan M
Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA.
Br J Pharmacol. 2007 Jul;151(6):798-806. doi: 10.1038/sj.bjp.0707278. Epub 2007 May 21.
The large-conductance Ca(2+)-activated K(+) channel (BK(Ca), K(Ca)1.1) links membrane excitability with intracellular Ca(2+) signaling and plays important roles in smooth muscle contraction, neuronal firing, and neuroendocrine secretion. This study reports the characterization of a novel BK(Ca) channel blocker, 2,4-dimethoxy-N-naphthalen-2-yl-benzamide (A-272651).
(86)Rb(+) efflux in HEK-293 cells expressing BK(Ca) was measured. Effects of A-272651 on BK(Ca) alpha- and BK(Ca) alphabeta1-mediated currents were evaluated by patch-clamp. Effects on contractility were assessed using low-frequency electrical field stimulated pig detrusor and spontaneously contracting guinea pig detrusor. Effects of A-272651 on neuronal activity were determined in rat small diameter dorsal root ganglia (DRG).
A-272651 (10 microM) inhibited (86)Rb(+) efflux evoked by NS-1608 in HEK-293 cells expressing BK(Ca) currents. A-272651 concentration-dependently inhibited BK(Ca) currents with IC(50) values of 4.59 microM (Hill coefficient 1.04, measured at +40 mV), and 2.82 microM (Hill coefficient 0.89), respectively, for BK(Ca) alpha and BK(Ca) alphabeta1-mediated currents. Like iberiotoxin, A-272651 enhanced field stimulated twitch responses in pig detrusor and spontaneous contractions in guinea pig detrusor with EC(50) values of 4.05+/-0.05 and 37.95+/-0.12 microM, respectively. In capsaicin-sensitive DRG neurons, application of A-272651 increased action potential firing and prolonged action potential duration.
These data demonstrate that A-272651 modulates smooth muscle contractility and neuronal firing properties. Unlike previously reported peptide BK(Ca) blockers, A-272651 represents one of the first small molecule BK(Ca) channel blockers that could serve as a useful tool for further characterization of BK(Ca) channels in physiological and pathological states.
大电导钙激活钾通道（BK(Ca)，K(Ca)1.1）将膜兴奋性与细胞内钙信号联系起来，在平滑肌收缩、神经元放电和神经内分泌分泌中发挥重要作用。本研究报告了一种新型BK(Ca)通道阻滞剂2,4 - 二甲氧基 - N - 萘 - 2 - 基 - 苯甲酰胺（A - 272651）的特性。
测量表达BK(Ca)的HEK - 293细胞中的(86)Rb(+)外流。通过膜片钳评估A - 272651对BK(Ca)α和BK(Ca)αβ1介导电流的影响。使用低频电场刺激的猪逼尿肌和自发收缩的豚鼠逼尿肌评估对收缩性的影响。在大鼠小直径背根神经节（DRG）中确定A - 272651对神经元活动的影响。
A - 272651（10 μM）抑制表达BK(Ca)电流的HEK - 293细胞中由NS - 1608诱发的(86)Rb(+)外流。A - 272651浓度依赖性地抑制BK(Ca)电流，对于BK(Ca)α和BK(Ca)αβ1介导的电流，IC(50)值分别为4.59 μM（希尔系数1.04，在 +40 mV测量）和2.82 μM（希尔系数0.89）。与埃博毒素一样，A - 272651增强了猪逼尿肌的场刺激抽搐反应和豚鼠逼尿肌的自发收缩，EC(50)值分别为4.05±0.05和37.95±0.12 μM。在辣椒素敏感的DRG神经元中，应用A - 272651增加了动作电位发放并延长了动作电位持续时间。
这些数据表明A - 272651调节平滑肌收缩性和神经元放电特性。与先前报道的肽类BK(Ca)阻滞剂不同，A - 272651是首批小分子BK(Ca)通道阻滞剂之一，可作为进一步表征生理和病理状态下BK(Ca)通道的有用工具。
