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家兔右室流出道心肌细胞的L-型钙电流

, PP. 196-202

Keywords: 心律失常,室性心动过速,右室流出道心肌细胞,L-型钙电流,早后除极,触发活动,膜片钳

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Abstract:

特发性室速主要起源于右室流出道(RVOT),目前对于此类心律失常的发生机制还不清楚.已有临床报告指出,源于右室流出道的心律失常,可能是基于触发性机制.但迄今为止,由于技术上的困难,对RVOT心肌细胞的实验研究极少,尚无法证实所推测的机制.L-型钙电流(ICa-L)是主要的内向电流之一,在心律失常的发生中起重要作用.本实验通过对家兔右室流出道心肌细胞ICa-L特性的研究,探索特发性右室流出道室速的可能发生机制.采用全细胞膜片钳技术记录RVOT和右心室(RV)心肌细胞的动作电位(AP)及ICa-L,并对比分析两者AP及ICa-L的特性.结果发现,RVOT心肌细胞AP离散度较RV大(RVOT,577.2±364.8ms;RV,386.2±163.4ms).在RVOT存在APD明显缩短和明显延长的心肌细胞.用4-AP阻断瞬时外向钾电流(Ito)后,未记录到APD明显缩短的细胞;而APD明显延长的细胞仍存在.少数RVOT细胞AP具有很长的平台甚至复极无法恢复到静息电位.它们能自发产生早后除极(EAD),可以诱发出第二平台反应;在RV中未记录到这种细胞;这些APD明显延长的RVOT心肌细胞与RV心肌细胞相比具有较大的ICa-L(13.16±0.87pA/pF,8.59±1.97pA/pF,P<0.05);用尼非地平(10μmol/L)阻断L-型钙通道后,ICa-L减小,动作电位时程缩短,RVOT心肌细胞记录到的长平台、EAD及第二平台反应消失.结果表明,RVOT心肌细胞APD离散度较RV心肌细胞大,是源于右室流出道的室速(RVOT-VT)的细胞电生理学基础.较大的Ito电流可能是导致RVOT心肌细胞APD明显缩短的原因之一;较强的ICa-L是导致RVOT动作电位明显延长的因素之一,并能出现EAD,这可能是RVOT产生触发性活动的机制之一.

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