钠钙交换体的电流-电压关系及稳态特性：八态连续转运模型的表征
Current-voltage relations and steady-state characteristics of Na+-Ca2+ exchange: characterization of the eight-state consecutive transport model.
作者信息
Omelchenko A, Hryshko L V
机构信息
St. Boniface General Hospital Research Centre, University of Manitoba, Winnipeg, Canada.
出版信息
Biophys J. 1996 Oct;71(4):1751-63. doi: 10.1016/S0006-3495(96)79376-1.
An analytical expression for Na+-Ca2+ exchange currents in cardiac cells has been obtained for an eight-state model. The equation obtained has been used to derive theoretical expressions for current-voltage relationships, maximum Na+-Ca2+ exchange currents, and half-saturating concentrations for Na+ and Ca2+. These equations were analyzed over a wide range of cytoplasmic and extracellular Na+ and Ca2+ concentrations, under forward and reverse "zero-trans" conditions. Correspondence of theoretical results with those obtained from giant excised patch experiments are presented. Rate constants from published reports were used to evaluate turnover rates for Na+-Ca2+ exchange in the forward and reverse directions. A factor, epsilon, is introduced that permits prediction of the extent to which the Na+-Ca2+ exchange cycle is under voltage or diffusion control. This factor can be conveniently used for data interpretation and comparison. The derived equations also provide a foundation for continuing experimental evaluation of the fidelity of this model.
已针对一个八态模型获得了心脏细胞中Na⁺-Ca²⁺交换电流的解析表达式。所得到的方程已用于推导电流-电压关系、最大Na⁺-Ca²⁺交换电流以及Na⁺和Ca²⁺的半饱和浓度的理论表达式。在正向和反向“零转运”条件下，对这些方程在广泛的细胞质和细胞外Na⁺和Ca²⁺浓度范围内进行了分析。给出了理论结果与从巨型分离膜片实验获得的结果的对应关系。使用已发表报告中的速率常数来评估正向和反向Na⁺-Ca²⁺交换的周转率。引入了一个因子ε，它可以预测Na⁺-Ca²⁺交换循环受电压或扩散控制的程度。这个因子可方便地用于数据解释和比较。所推导的方程也为继续对该模型的逼真度进行实验评估提供了基础。
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