Vassort G, Horackova M, Mongo K, Roulet M J, Ventura-clapier R
Pathol Biol (Paris). 1979 Jan;27(1):21-9.
It has been realized for a century that Ca2+ is important in the initiation and the control of mechanical activity. The present paper does not cover the field of excitation-contraction coupling in heart but mainly reports some modern and controversial aspects about the regulation of the internal Ca concentration by the sarcolemma while the role of internal stores is only discussed. The first part deals with flux experiments; the second with the slow inward current mainly carried by Ca ions. An analysis of the mechanical activity reveals that only a part of tension is triggered by this slow current; besides, a second component of tension is demonstrated and an exchange mechanism of Na and Ca ions is described in detail. This countertransport, during depolarization, facilitates an influx of Ca ions (coupled to an efflux of Na ions). During hyperpolarization, or even at the resting membrane potential, it promotes an efflux of Ca ions. Thus, the same mechanism may account in part for the development or for the relaxation of tension according to the membrane potential.
一个世纪以来，人们已经认识到Ca2+在机械活动的启动和控制中起着重要作用。本文不涉及心脏兴奋-收缩偶联领域，主要报道关于肌膜对细胞内Ca浓度调节的一些现代且有争议的方面，同时仅讨论细胞内钙库的作用。第一部分涉及通量实验；第二部分涉及主要由Ca离子携带的缓慢内向电流。对机械活动的分析表明，只有一部分张力是由这种缓慢电流触发的；此外，还证明了张力的第二个组成部分，并详细描述了Na和Ca离子的交换机制。这种逆向转运在去极化期间促进Ca离子内流（与Na离子外流耦合）。在超极化期间，甚至在静息膜电位时，它促进Ca离子外流。因此，根据膜电位，相同的机制可能部分解释张力的产生或松弛。
