Preferential loss of EC coupling gradation at positive membrane potentials in rat ventricular myocytes.
Preferential loss of EC coupling gradation at positive membrane potentials in rat ventricular myocytes.
复制标题
大鼠心室肌细胞膜电位正时 EC 耦合梯度优先丧失。
DOI：
10.1007/s00424-002-0857-2
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Palade,Philip
中科院分区：
文献类型：
--
作者：
Fan,Jing-Song;Palade,Philip
大鼠心室肌细胞从含有 1 mM 细胞外 Ca 的溶液转换为含有 5 mM 细胞外 Ca 的溶液，表现出更大的 Ca 电流，失活更快。它们的 Ca 瞬变表现出较慢的衰减。在一些细胞中，Ca 瞬变的幅度显着增加，但在其他细胞中则没有。引人注目的是，在大约一半的检查细胞中，在正膜电位范围内的 Ca 瞬变的分级性质消失了，复极化时引起的 Ca 瞬变也消失了。这些变化是显而易见的，在负膜电位范围（–35 至 0 mV）内没有等效的梯度损失。这种正膜电位梯度的优先损失也发生在缺乏细胞外和/或细胞内Na的溶液中，并且被硝苯地平消除。结果表明，如果 Ca 进入触发增加，Ca 诱导的 Ca 在正电位下从 SR 释放可以饱和或变得再生。在负电位下缺乏类似的作用表明大量激活的 L 型通道对于诱导再生行为至关重要。
Rat ventricular myocytes switched from a solution containing 1 mM extracellular Ca to one containing 5 mM extracellular Ca exhibited larger Ca currents that inactivated more rapidly. Their Ca transients exhibited a slower decay. In some cells the amplitude of the Ca transients increased markedly, but not in others. Strikingly, in about half the cells examined, the graded nature of the Ca transients over the range of positive membrane potentials was lost, as were Ca transients elicited upon repolarization. These changes were manifest without equivalent loss of gradation over the range of negative membrane potentials (–35 to 0 mV). Such preferential loss of gradation at positive membrane potentials also occurred in solutions devoid of extracellular and/or intracellular Na, and was abolished by nifedipine. The results suggest that Ca-induced Ca release from the SR at positive potentials can saturate or become regenerative if the Ca entry trigger is increased. The lack of a similar effect at negative potentials indicates that large numbers of activated L-type channels are critical for induction of regenerative behavior.