Mullins L J
Am J Physiol. 1979 Mar;236(3):C103-10. doi: 10.1152/ajpcell.1979.236.3.C103.
The presence of a detectable Ca current during the excitation of a cardiac fiber implies that the Ca lost during the resting interval of the duty cycle must also be detectable. Ca outward movement appears to be effected by Na/Ca exchange when more Na enters than Ca leaves per cycle, thus making the mechanism electrogenic. Since Na/Ca exchange can move Ca either inward or outward depending on the direction of the electrochemical gradient for Na, a potential exists where there is no electric current generated by the Na/Ca exchange mechanism, i.e., a reversal potential ER. Cardiac fibers appear to have a reversal potential that is about midway between their resting membrane potential and their plateau. Carrier currents both inward and outward are therefore generated during cardiac action potentials. The implications of the conditions stated above are explored.
在心脏纤维兴奋期间存在可检测到的钙电流，这意味着在占空比的静息间隔期间丢失的钙也必须是可检测的。当每个周期进入的钠比离开的钙多时，钙的外向运动似乎是由钠/钙交换实现的，从而使该机制具有生电性。由于钠/钙交换可根据钠的电化学梯度方向使钙向内或向外移动，所以存在一个由钠/钙交换机制不产生电流的电位，即反转电位ER。心脏纤维似乎具有一个约在其静息膜电位与其平台期电位中间的反转电位。因此在心脏动作电位期间会产生内向和外向的载体电流。本文探讨了上述情况的影响。
