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Zacopride通过PKA途径选择性激动大鼠心肌Kir2.1通道

, PP. 753-761

Keywords: zacopride,内向整流钾通道,5-HT受体,蛋白激酶

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Abstract:

前期研究发现促胃肠动力药zacopride(5-HT4受体激动剂兼5-HT3受体拮抗剂)通过选择性激动大鼠心室肌内向整流钾电流(inwardrectifierpotassiumcurrent,IK1)表现出抗室性心律失常无房性致心律失常作用,本研究旨在探讨zacopride这一独特的药理特性的分子机制.采用胶原酶法急性分离大鼠心房肌细胞;利用全细胞膜片钳技术观察zacopride对大鼠心房肌细胞IK1电流、细胞跨膜电位和在HEK293细胞上表达的大鼠心肌Kir2.1,Kir2.2,Kir2.3通道和磷酸化位点突变的Kir2.1(S425L)通道的效应,以及干预5-HT受体和干预PKA,PKC,PKG信号通路的工具药对zacopride调节IK1作用的影响.运用WesternBlot分析大鼠心房肌及心室肌kir2.x通道构成.结果表明,zacopride对大鼠心房肌细胞IK1电流及跨膜电位无显著影响;可使HEK293细胞上表达的同源Kir2.1外向电流增加40.7%±9.7%(在-50mV,P<0.01),而对同源Kir2.2、同源Kir2.3及异源Kir2.1+Kir2.2,Kir2.1+Kir2.3和Kir2.2+Kir2.3通道电流均无明显作用.WesternBlot分析显示,Kir2.3表达量在大鼠心房及心室无明显差异,而大鼠心房Kir2.1的表达量仅为心室相应量的25%;HEK293细胞上5-HT3受体缺失,5-HT4受体呈低表达水平.PKA抑制剂能够显著抑制zacopride激动Kir2.1电流的效应,而PKC,PKG抑制剂不能影响这一效应;zacopride在-50mV可使Kir2.1S425L突变体电流增加13.3%±6.5%,但无统计学意义(P>0.05).以上结果提示,zacopride激动Kir2.1电流的效应是经AC/cAMP/PKA信号通路介导的,而与其对5-HT3和5-HT4受体的作用无关.

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