Delayed rectifier potassium current (IK) in latent atrial pacemaker cells isolated from cat right atrium.
Delayed rectifier potassium current (IK) in latent atrial pacemaker cells isolated from cat right atrium.
复制标题
从猫右心房分离的潜伏心房起搏细胞中的延迟整流钾电流 (IK)。
DOI：
10.1007/bf00374791
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Lipsius,SL
中科院分区：
文献类型：
--
作者：
Zhou,Z;Lipsius,SL
采用全细胞记录技术研究从猫右心房分离的潜伏起搏细胞中的延迟整流 K+ 电流 (IK)。从 -40 mV 的保持电位开始，去极化钳步骤引起 L 型 Ca2+ 电流，随后外向电流 (IK) 增加。尾电流幅度的时间过程与外向电流的时间依赖性激活的时间过程平行。 IK 的激活表现出 S 形时间过程，最适合幂函数，其中激活变量提高到二次幂。 IK激活的电压依赖性在-40和+30 mV之间表现出S形关系。半最大激活电压和斜率因子分别为-21.9±1.3和13.8±0.9 mV (n=6)。 IK 完全激活的 I/V 关系在 -100 和 -30 mV 之间呈线性，并在更正的电压下进行内向整流。 IK 激活后，负性超过约 -50 mV 的超极化引发了由 IK 失活和 If 激活组成的尾电流。使用减法方案来分离 IKtail 电流。在 5.4 mM 细胞外 [K+] 中，IKtail 电流表现出 -78.2±0.3 mV (n=6) 的反转电位。 IK 的反转电位与细胞外 [K] 的对数呈线性相关，细胞外 [K] 每变化 10 倍，斜率为 51.5 mV。在−70 mV 时，IKtail 电流以单指数函数形式衰减，时间常数为159±16 ms (n=6)。这些结果表明，潜在的心房起搏器表现出由去极化激活的 IK。IK 似乎由一种电流成分组成。在与最大舒张电位 (−70 mV) 兼容的电压下，IK 尾电流相对较小，并且 IK 衰减比 If 激活快得多。我们的结论是，在右心房潜在起搏器中，IK 可能有助于动作电位的复极化和起搏器电位初始阶段的时间进程。
Whole-cell recording techniques were used to study the delayed rectifier K+current (IK) in latent pacemaker cells isolated from cat right atrium, From a holding potential of −40 mV, depolarizing clamp steps elicited L-type Ca2+current followed by an increasing outward current (IK). The time course of tail current amplitudes parallelled that of the time-dependent activation of outward current. Activation ofIKexhibited a sigmoidal time course that was best fit by a power function where the activation variable was raised to the second power. The voltage-dependence ofIKactivation exhibited a sigmoidal relationship between −40 and +30 mV. The half-maximal activation voltage and slope factor were −21.9±1.3 and 13.8±0.9 mV respectively (n=6). The fully activatedI/Vrelationship ofIKwas linear between −100 and −30 mV and inwardly rectified at more positive voltages. FollowingIKactivation, hyperpolarizations more negative than about −50 mV elicited tail currents that consisted of bothIKdeactivation andIfactivation. A subtraction protocol was used to isolateIKtail currents. In 5.4 mM extracellular [K+],IKtail currents exhibited a reversal potential of −78.2±0.3 mV (n=6). The reversal potential ofIKwas linearly related to log extracellular [K] and the slope was 51.5 mV per ten-fold change in extracellular [K]. At −70 mV,IKtail currents decayed as a single exponential function with a time constant of 159±16 ms (n=6). These results indicate that latent atrial pacemakers exhibitIKactivated by depolarization.IKappears to consist of one current component. At voltages compátible with the maximum diastolic potential (−70 mV)IKtail currents are relatively small andIKdecays much more rapidly thanIfactivation. We conclude that in right atrial latent pacemakersIKmay contribute to repolarization of the action potential and the time course of the initial phase of the pacemaker potential.