Regulation of the Na-conducting Ca channel during the cardiac action potential.
Regulation of the Na-conducting Ca channel during the cardiac action potential.
复制标题
心脏动作电位期间钠传导钙通道的调节。
DOI：
10.1016/s0006-3495(87)83316-7
复制
发表时间：
1987
影响因子：
3.4
通讯作者：
DeFelice,LJ
中科院分区：
文献类型：
--
作者：
Mazzanti,M;DeFelice,LJ
本文报道了在跳动的心肌细胞自发动作电位和非搏动状态的模拟动作电位中，安娜传导通道的动力学特征。由于该通道仅在钙浓度低于10(-6)M时传导Na，且对河豚毒素不敏感，在133 mM Na中具有100ps的电导，因此我们将其确定为在零钙条件下传导Na的钙通道。通过比较搏动和非搏动细胞的通道，但在两种情况下都经历相同电压的条件下，我们观察到：搏动和非搏动细胞的开放通道电导相同；搏动细胞的通道反转电位为25 mV，非搏动细胞的通道反转电位为50 mV；搏动细胞的平均电流峰值比未搏动细胞的平均电流峰值晚，并且在两种情况下有不同的时间进程，这不能单独用反转电位的移动来解释；在动作电位期间，通过搏动细胞的平均钠通道电流达到峰值的时间比我们预期的通道携带钙的时间要晚得多。我们的结论是，当钙通道传导Na时，其动力学和翻转电位受到伴随搏动的细胞质因素的强烈影响，其行为不是仅受电压的支配。我们还得出结论，当钙通道传导Na时，它的反转电位和电导不仅与携带钙的通道相比发生了变化，而且通道的动力学依赖于离子。由于只有斑块中的钙通道处于零钙并传导Na，而斑块周围的钙通道处于1.5 mm的钙通道中并正在传导钙，我们的数据支持这样的观点，即只有通过单个通道的钙才会影响这些相同通道的动力学。
This paper describes the kinetics of an Na-conducting channel during spontaneous action potentials in beating heart cells and during simulated action potentials driven from the patch when the cell is not beating. Since the channel conducts Na only in Ca concentrations below 10(-6) M, and since it is insensitive to tetrodotoxin and has a conductance of 100 pS in 133 mM Na, we identify it as the Ca channel conducting Na in zero Ca. By comparing the channel in beating and nonbeating cells, but under conditions in which it experiences the same voltage in both cases, we observe that: open-channel conductance is the same in beating and nonbeating cells; the channel reversal potential is 25 mV in beating cells and 50 mV in nonbeating cells; the average current peaks later in beating cells than in nonbeating cells, and it has a different time course in the two cases that is not explained by the shift in reversal potential alone; and the average Na current through Ca channels in beating cells peaks much later during the action potential than we would expect if the channel were carrying Ca. We conclude that when the Ca channel conducts Na, its kinetics and reversal potential are strongly influenced by cytoplasmic factors that accompany beating, and that its behavior is not governed by voltage alone. We also conclude that when the Ca channel conducts Na, not only are its reversal potential and conductance altered from what they would be were the channel carrying Ca, but also the channel's kinetics depend on the permeant ion. Since only the channels in the patch are in zero Ca and are conducting Na, while the Ca channels surrounding the patch are in 1.5 mM Ca and are conducting Ca, our data support the idea that it is only the Ca passing through individual channels that influences the kinetics of those same channels.