家兔右室流出道心肌细胞的L-型钙电流

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

Difference in Current Densities of Two Pore Domain Potassium Channel between Ventricular and Ventricular Outflow Tract Cardiomyocytes in Rabbit Heart

目的已知特发性室速主要起源于右室流出道(rVOT),由于技术上的困难,目前对特发性右室流出道室速(rVOT-VT)的离子通道机制研究很少,本实验意在探索右室心室肌(rV)和rVOT的双孔钾通道电流(Ik2P)的特性及其在rVOT-VT发生机制中可能参与的作用。方法采用全细胞膜片钳技术记录右室和右室流出道心肌细胞的单细胞电流。结果 rVOT的稳态外向电流较右室的小。对稳态电流进一步研究发现,右室流出道和右室心肌细胞上均存在Ik2P。右室流出道细胞的Ik2P电流密度明显小于右室细胞。结论首次在电生理水平上,证实了家兔右室心肌细胞上存在Ik2P,rVOT心肌细胞的Ik2P电流密度小于rV心肌细胞,是构成右室流出道APd离散度增大及外向电流降低的基础,从而易出现EAd,进而促进rVOT-VT的发生。Objective Idiopathic ventricular tachycardia mainly originates from right ventricular outflow tract(RVOT).The ionic channel mechanism of idiopathic ventricular tachycardia arising from right ventricular outflow tract(RVOT-VT)has been seldom reported experimentally,for the technical difficulties.The aim of the experiment was to explore the difference of IK2p between the myocardial cells in RVOT and free right ventricular wall(RV)in rabbit heart and the mechanism of the ventricular tachycardia genesis from RVOT.Methods The ionic currents of rabbit cardiomyocytes in RVOT and in RV were recorded with the whole-cell patch-clamp technique.Results The steady-state current in RVOT cardiomyocytes was less than that in RV.The further observation on the steady-state current showed that IK2p currents existed in rabbit RVOT and RV myocardial cells,displaying that IK2p current in RVOT was less than that in RV.Conclusion It was the first time on the electrophysiological level verified the existence of the IK2p current in rabbit.The low IK2p current density in some RVOT myocytes led to lower the outward current and prolonged APD in RVOT myocytes.These might induce EAD and resulted to genesis of RVOT-VT

The properties of action potential and sodium-calcium exchange tail current of rabbit right ventricular outflow tract myocytes

目的研究兔右室流出道(rVOT)心肌细胞动作电位及钠钙交换尾电流(InCX,TAIl)相关特性,探讨源于rVOT室性心律失常的发生机制。方法采用全细胞膜片钳技术记录兔右室(rV)游离壁和rVOT心肌细胞的动作电位,在不更换细胞及电极内液情况下连续记录InCX,TAIl,对比分析两者动作电位和InCX,TAIl特性。结果兔rVOT心室肌细胞动作电位复极时程(APd)的变异程度大于rV游离壁心肌细胞。在rVOT心肌细胞记录到早期后除极及显著延长的APd。动作电位显著延长及后除极的rVOT心肌细胞所对应的InCX,TAIl到达峰值时程较动作电位正常的细胞延迟,并且电流强度大于rV游离壁对照组心肌细胞(P<0.05)。结论 rVOT心肌细胞APd变异程度大,而且APd显著延长的rVOT细胞InCX,TAIl到达峰值时程延迟及相应电流显著增大,这是rVOT部位好发触发活动的重要机制。Objective To explore the electrophysiological basis of arrhythmogenesis in right ventricular outflow tract(RVOT) myocytes of rabbit heart.The properties of action potential and sodium-calcium exchange tail current(INCX,tail) in rabbit RVOT cells were observed.Methods Patch-clamp technique was used to measure INCX,tail and action potential in single myocytes obtained by enzymatic dispersion of rabbit ventricle.Results Marked variability of action potential repolarization was observed in rabbit RVOT cardiomyocytes.The events of early afterdepolarization(EAD) and marked action potential duration(APD) extension were recorded in RVOT cells.The peak of INCX,tail was delayed significantly in marked APD extension RVOT cells compared to RV free wall cells,and the amplitude of INCX,tail in the former was larger than the latter ones(P<0.05).Conclusion In rabbit RVOT cardiomyocytes,prolonged APD might be the induction factor of delayed afterdeporization and EAD genesis.Under this precondition,the late-peaking and larger amplitude of INCX,tail in RVOT cells might play pivotal role in the mechanism of RVOT arrhythmogenesis.厦门市卫生局资助项目(No.A0000258