Pidoplichko V I, Verkhratsky A N
Gen Physiol Biophys. 1987 Jun;6(3):223-35.
Cardiomyocytes enzymatically isolated from rat and guinea pig ventricular tissue were investigated under conditions of intracellular perfusion and voltage clamp at 18-20 degrees C. Perfusion with 135 mmol/l Tris(HF), pH 7.2 was used to eliminate outward potassium currents. The dependence of inward current (elicited by depolarizing pulses from a holding potential level of--120 mV) on low external TTX concentrations (from 10(-13) to 10(-10) mol/l) was studied. Similar TTX concentrations increased the amplitude of the inward current and changed its kinetics in a large number of cells tested. The effect was fully reversible. The effect could be evaluated in a net form by digital subtraction of the current obtained after the application of a low external TTX concentration from the initial current in a TTX-free solution. The TTX concentration dependence of the difference current could be fitted by one-to-one binding curve with Kd = (1.0 +/= 0.4) x 10(-12) mol/l. TTX-induced current changes were absent in low sodium or chloride-free external solutions. The outward current (a block of which by TTX produced the inward current changes observed) showed a reversal potential consistent with the chloride nature of such a current. The existence of a transient TTX-sensitive Na-dependent potential gated chloride current in the membrane of isolated cardiomyocytes is postulated.
在18 - 20摄氏度的细胞内灌注和电压钳条件下，对从大鼠和豚鼠心室组织中酶解分离出的心肌细胞进行了研究。用pH 7.2的135 mmol/l Tris(HF)灌注以消除外向钾电流。研究了内向电流（由从 - 120 mV的钳制电位水平去极化脉冲引发）对低浓度外部TTX（从10(-13)到10(-10) mol/l）的依赖性。在大量测试细胞中，类似的TTX浓度增加了内向电流的幅度并改变了其动力学。该效应是完全可逆的。通过从无TTX溶液中的初始电流中减去施加低浓度外部TTX后获得的电流，可以以净形式评估该效应。差电流的TTX浓度依赖性可以用Kd = (1.0 ± 0.4) x 10(-12) mol/l的一对一结合曲线拟合。在低钠或无氯的外部溶液中不存在TTX诱导的电流变化。外向电流（其被TTX阻断产生了观察到的内向电流变化）显示出与该电流的氯离子性质一致的反转电位。推测在分离的心肌细胞膜中存在瞬时TTX敏感的钠依赖性电位门控氯电流。
