Luo C H, Rudy Y
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-7207.
Circ Res. 1994 Jun;74(6):1097-113. doi: 10.1161/01.res.74.6.1097.
The action potential model presented in our accompanying article in this journal is used to investigate phenomena that involve dynamic changes of [Ca2+]i, as described below. Delayed afterdepolarizations (DADs) are induced by spontaneous Ca2+ release from the sarcoplasmic reticulum (SR), which, in turn, activates both the Na(+)-Ca2+ exchanger (INaCa) and a nonspecific Ca(2+)-activated current (Ins(Ca)). The relative contributions of INaCa and of Ins(Ca) to the generation of DADs are different under different degrees of Ca2+ overload. Early afterdepolarizations (EADs) can be categorized into two types: (1) plateau EADs, resulting from a secondary activation of the L-type Ca2+ current during the plateau of an action potential, and (2) phase-3 EADs, resulting from activation of INaCa and Ins(Ca) by increased [Ca2+]i due to spontaneous Ca2+ release from the SR during the late repolarization phase. Spontaneous rhythmic activity and triggered activity are caused by spontaneous Ca2+ release from the SR under conditions of Ca2+ overload. Postextrasystolic potentiation reflects the time delay associated with translocation of Ca2+ from network SR to junctional SR. The cell is paced at high frequencies to investigate the long-term effects on the intracellular ionic concentrations.
在本期刊随附文章中提出的动作电位模型用于研究涉及[Ca2+]i动态变化的现象，如下所述。延迟后去极化（DADs）由肌浆网（SR）自发释放Ca2+诱导，这反过来又激活Na(+)-Ca2+交换体（INaCa）和非特异性Ca(2+)-激活电流（Ins(Ca)）。在不同程度的Ca2+超载情况下，INaCa和Ins(Ca)对DADs产生的相对贡献有所不同。早期后去极化（EADs）可分为两种类型：（1）平台期EADs，由动作电位平台期L型Ca2+电流的二次激活引起；（2）3期EADs，由复极化后期SR自发释放Ca2+导致[Ca2+]i升高激活INaCa和Ins(Ca)引起。自发节律性活动和触发活动由Ca2+超载条件下SR自发释放Ca2+引起。早搏后增强反映了Ca2+从网络型SR转运到连接型SR的时间延迟。以高频对细胞进行起搏以研究对细胞内离子浓度的长期影响。
