Veldkamp M W, van Ginneken A C, Bouman L N
Department of Physiology, University of Amsterdam, The Netherlands.
Circ Res. 1993 Apr;72(4):865-78. doi: 10.1161/01.res.72.4.865.
In rabbit ventricular cells, the delayed rectifier current (IK) has not been extensively studied, and properties of single IK channels still need to be determined. In this study, we present data on a voltage-dependent channel in rabbit ventricular cells; the properties indicate that it is an IK channel. Patch-clamp experiments were carried out on cell-attached and inside-out patches of rabbit ventricular cells. Single-channel currents were recorded at negative potentials as inward currents with 150 mM K+ in the pipette. Voltage-dependent channel activity was only present after the return from a depolarizing test pulse, indicating activation on depolarization. Single-channel conductance calculated from the current-voltage relation was 13.1 pS (pooled data, n = 8). The shift in reversal potential of the unitary currents, determined at 150 and 300 mM K+ at the intracellular side of the membrane, showed that the channels were highly permeable to potassium ions. Increase of the duration or the amplitude of the depolarizing test pulse increased channel activity. The time constant for activation at +30 mV was 187 msec (pooled data, n = 4). Half-activation potential was -4.9 +/- 3.8 mV (mean +/- SD), and the slope factor was 7.2 +/- 3.7 mV (mean +/- SD). Current tails, reconstructed from averaged single-channel currents, revealed that the time course of deactivation decreased from 694 +/- 73 msec at -80 mV to 136 +/- 39 msec at -110 mV. Additional evidence that the channel was indeed an IK channel was provided by the observation that the channel was blocked by 10(-7) M E-4031, a class III antiarrhythmic agent that has been shown to block a component of the macroscopic IK in guinea pig heart.
在兔心室肌细胞中，延迟整流电流（IK）尚未得到广泛研究，单个IK通道的特性仍有待确定。在本研究中，我们展示了兔心室肌细胞中一种电压依赖性通道的数据；这些特性表明它是一个IK通道。我们对兔心室肌细胞的细胞贴附式和内面向外式膜片进行了膜片钳实验。在吸管中含有150 mM K+的情况下，在负电位下记录单通道电流作为内向电流。电压依赖性通道活性仅在去极化测试脉冲返回后出现，表明在去极化时激活。根据电流-电压关系计算的单通道电导为13.1 pS（汇总数据，n = 8）。在膜内侧150 mM和300 mM K+浓度下测定的单通道电流反转电位的变化表明，该通道对钾离子具有高度通透性。去极化测试脉冲持续时间或幅度的增加会增加通道活性。在+30 mV时激活的时间常数为187毫秒（汇总数据，n = 4）。半激活电位为-4.9 +/- 3.8 mV（平均值 +/- 标准差），斜率因子为7.2 +/- 3.7 mV（平均值 +/- 标准差）。从平均单通道电流重建的电流尾表明，失活的时间进程从-80 mV时的694 +/- 73毫秒降至-110 mV时的136 +/- 39毫秒。观察到该通道被10^(-7) M E-4031阻断，这为该通道确实是IK通道提供了额外证据，E-4031是一种III类抗心律失常药物，已被证明可阻断豚鼠心脏中宏观IK的一个成分。
