Filippov A K, Tertishnikova S M, Bouquet T I, Porotikov V I, Ilyin V I
Chemical Products Biological Testing Research Institute, Kupavna, Moscow, USSR.
Gen Physiol Biophys. 1988 Feb;7(1):29-38.
Electrical and mechanical responses of frog atrial trabeculae were studied simultaneously using the double-sucrose gap method. Action potentials and twitch tension could be successively generated in fibers in which the slow inward calcium channel current was not observed. As a rule, this could be obtained in the course of a long experiment (3 to 4 hours). Peak tension was shown to increase monotonically with membrane potential in these preparations. In preparations with the slow inward current the total peak tension could be separated into two components. The first component (tonic) monotonically increased with the membrane potential and was probably related to Na/Ca exchange (Horackova 1984). The potential dependency of the second (phasic) component correlated with that of the slow inward calcium current. Only the tonic but not the phasic component could be observed in preparations without the presence of the slow inward calcium current. The tonic component prevailed when both the slow inward current and phasic tension were greatly reduced by nifedipine. Long experiments, long depolarizing clamp pulses, a metabolic inhibitor 2,4-dinitrophenol, inhibitors of Na/K pump ouabain and AR-L57, toxins promoting intracellular sodium accumulation (aconitine, scorpion toxin) were all shown to increase the tonic tension, but not the slow inward current; they induced a transition from biphasic tension-voltage curve into a monotonically increasing one. We concluded that these procedures and agents greatly stimulate Ca influx via Na/Ca exchange. These results show that Na/Ca exchange can function as a reserve system of Ca2+ used for contraction, thus supporting the heart function, especially under unfavourable metabolic conditions.
采用双蔗糖间隙法同时研究了蛙心房小梁的电反应和机械反应。在未观察到慢内向钙通道电流的纤维中，可以相继产生动作电位和抽搐张力。通常，这可以在长时间实验（3至4小时）过程中获得。在这些标本中，峰值张力显示出随膜电位单调增加。在具有慢内向电流的标本中，总峰值张力可分为两个成分。第一个成分（张力性）随膜电位单调增加，可能与钠/钙交换有关（霍拉科娃，1984年）。第二个（相位性）成分的电位依赖性与慢内向钙电流的电位依赖性相关。在没有慢内向钙电流的标本中，只能观察到张力性成分而不是相位性成分。当慢内向电流和相位性张力都被硝苯地平大大降低时，张力性成分占主导。长时间实验、长去极化钳制脉冲、代谢抑制剂2,4-二硝基苯酚、钠/钾泵抑制剂哇巴因和AR-L57、促进细胞内钠积累的毒素（乌头碱、蝎毒素）均显示可增加张力性张力，但不增加慢内向电流；它们诱导了从双相张力-电压曲线向单调增加曲线的转变。我们得出结论，这些程序和药物极大地刺激了通过钠/钙交换的钙内流。这些结果表明，钠/钙交换可以作为用于收缩的钙的储备系统发挥作用，从而支持心脏功能，尤其是在不利的代谢条件下。
