异丙肾上腺素对兔右心室心外膜下心肌细胞电生理机制的影响

目的文献报道一些Brugada综合征（Brugadasyndrome，BS）患者使用异丙肾上腺素（isoproterenol，Iso）能够减轻耵段抬高，抑制窒性心律失常和电风暴的发生。本文对Iso这一作用的细胞电生理机制进行研究。方法酶解法分离兔右心室外膜下心肌（sub-epieardium，Epi）细胞。采用全细胞膜片钳技术记录1μmol Iso作用前后动作电传（actionpotential，AP）、L型钙电流（L—typecalciumeH／TeRt，ICaL）及短暂外向钾电流（transient outward potassiumcurrent，Ito）的变化。结果①Iso显著延长动作电位时限（APD）；②Iso使Ito峰值从（11．4±1．7）pA／pF减少到（6．3±0．5）pA／pF（n=16，P〈0．05），使Ito I—V曲线下移，稳态失活曲线左移及失活后恢复曲线右移；③Iso使ICaL峰值从（-6．1±0．6）pA／pF增加到（-8．64-0．9）pA／pF（n=10，P〈0．05），使I—V曲线下移。结论Iso呈电压依赖性抑制Ito和增加ICaL，延长APD，这可能与Iso能够减轻BS患者ST段抬高，抑制Bs患者窄性心律失常和电风暴的发生有关。

Effects of isoproterenol on ionic mechanisms of epicardial myocytes in right ventricle in rabbits

Objective To investigate the effect of isoproterenol(Iso)on action potential duration (APD),L-type calcium current(ICaL)andtransient outwardpotassium current(Ito).Methods Single sub-epicardial myocytcs of right ventricle in rabbits were isolated with enzymatic dissociation.The whole-cell patch clamp recording technique was used.Results(1)Iso significantly prolonged APD.(2)Peak Ito decreased from(11.4±1.7)pA/pF to(6.3±0.5)pA/pF(n=16,P<0.05)after using Iso.Iso downshifted the I-V curves of Ito,turned the steady=state inactication curve to left and moved the curve of time recovery from inactivation to risht.(3)Iso increased peak,ICaL from(-6.1±0.6)pA/pF to(-8.6±0.9)pA/pF(n=10,P<0.05)and downshifted the I-V curves.Conclusions Iso could block Ito and augment ICaL in a voltage-dependent manner and prolong APD,which could be the mechanisms of its suppressing ventricular arrhythmia and electrical storm of Brugada syndrome.