Electrophysiological effect and the gating mechanism of astragaloside IV on L-type Ca2+ channels of guinea-pig ventricular myocytes
Electrophysiological effect and the gating mechanism of astragaloside IV on L-type Ca2+ channels of guinea-pig ventricular myocytes
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黄芪甲苷对豚鼠心室肌细胞L型Ca2+通道的电生理作用及门控机制
DOI：
10.1016/j.ejphar.2015.03.082
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发表时间：
2015-08-05
影响因子：
5
通讯作者：
Hao, Liying
中科院分区：
文献类型：
--
作者：
Zhao, Meimi;Shao, Dongxue;Hao, Liying
黄芪甲苷（AS-IV）是黄芪的主要活性成分之一。本研究旨在探讨AS-Ⅳ对单个心肌细胞及单个钙通道活性的影响。采用全细胞膜片钳技术测定新鲜分离的心肌细胞全细胞钙电流。在细胞贴附贴片和由内向外贴片中检查单钙通道电流。在全细胞记录中，AS-IV以浓度依赖的方式降低L型钙电流（I-CaL）的幅度。虽然AS-IV没有改变稳态激活曲线，但电流失活曲线的电压依赖性以浓度依赖性方式被AS-IV负移。与全细胞记录的结果一致，在由内而外的配置中，通过L型Ca 2+通道的单个Ba 2+电流的整体平均值被AS-IV剂量依赖性地降低。在0.1或1 μ M的AS-IV的单位Ba ~（2+）电流的减少被解释为通道活性（NPo）的降低。除了NPo的减少之外，还有Po的减少，而通道数量没有变化，单通道电流也没有明显变化。此外，我们还发现通道的开闭动力学受AS-IV的影响。AS-IV诱导L-型钙通道从短暂开放（模式1）或持久开放（模式2）转变为无主动开放（模式0）。我们的结果表明，AS-IV通过影响L型Ca ~（2+）通道的开闭动力学来抑制通道活动，从而阻断豚鼠心室肌细胞Ca ~（2+）通道电流。本研究可为黄芪单体的药物开发提供理论依据。(C)2015 Elsevier B. V.版权所有。
Astragaloside IV (AS-IV) is one of the main active ingredients of Astragalus membranaceus. This study is aimed to investigate AS-IV's effects on Ca2+ channel activity of single cardiomyocytes and single Ca2+ channels. Whole-cell Ca2+ currents in freshly dissociated cardiomyocytes were measured using the whole-cell patch-clamp technique. Single Ca2+ channel currents were examined in cell-attached patches and inside-out patches. In the whole-cell recording, AS-IV reduced the amplitude of L-type Ca2+ currents (I-CaL) in a concentration-dependent manner. Although AS-IV did not alter the steady-state activation curves, the voltage dependence of the current inactivation curves was negatively shifted by AS-IV in a concentration dependent manner. Consistent with the results of the whole-cell recording, in the inside-out configuration the ensemble average of single Ba2+ current via L-type Ca2+ channel was dose-dependently reduced by AS-IV. The reduction of unitary Ba2+ current at 0.1 or 1 mu M AS-IV was accounted for a decrease in the channel activity (NPo). In addition to the decrease in NPo, there was a reduction of Po without a change in channel number or an apparent change in single channel current. Furthermore, we found that the open-closed kinetics of the channel were affected by AS-IV. AS-IV induced the shift of L-type Ca2+ channels from either brief openings (mode 1) or long-lasting openings (mode 2) to no active opening (mode 0). Our results suggest that AS-IV blocks the currents through Ca2+ channels in guinea-pig ventricular myocytes by affecting the open-closed kinetics of L-type Ca2+ channels to inhibit the channel activities. This study could provide theoretical basis for the drug exploiting of the monomer of Astragalus membranaceus. (C) 2015 Elsevier B.V. All rights reserved.