摘要
目的 研究细胞外 Zn2 +对非洲爪蟾卵母细胞表达的内向整流钾通道 (IRK1)的阻断作用 .方法 采用双微电极电压钳 (TEV )法 .结果 细胞外 Zn2 +浓度分别为 0 ,0 .1,0 .2 5 ,1,3,10和 2 0 mmol· L- 1 ,K+浓度为 90 m mol· L- 1时 ,可见 Zn2 +对 IRK1的瞬间电流 (施加电压后 2 ms)具有Zn2 +浓度依赖性、时间依赖性和电压依赖性阻断作用 ;阻断剂Zn2 +对 IRK1的门控特性和外向电流几乎无影响作用 ;细胞外加 Zn2 +后反转电位没有变化 ,因而 IRK1对之不通透 ;细胞外 Zn2 +可增加 IRK1的归一化电导 .三级指数拟合的结果提示 :细胞外 Zn2 +对 IRK1的抑制作用可能通过表面电荷机制或通过阻断通道表面位点 .因为 Zn2 +浓度较低时 ,阻断大小与 Zn2 +浓度时差异不大 ,所以 Zn2 +不会通过表面电荷机制进行 IRK1阻断的 .结论 Zn2 +是 IRK1的一种快速开放通道阻断剂 。
AIM To study the blocking effects of extracell ular Zn 2+ on the inward rectifier potassium channel (IRK1), Xenopus oocytes expression system was used. METHODS Two microelectrode voltage clamp (TEV) method was used. RESULTS Zn 2+ could concentration, time and voltage dependently block IRK1 instantaneous currents (2 ms after voltage applied) when external Zn 2+ concentration was 0, 0.1, 0.25, 1, 3, 10 or 20 mmol·L -1 with K + concentration fixed to 90 mmol·L -1 . Zn 2+ almost had no effect on the gating property and outward currents of IRK1. Zn 2+ could concentration dependently increase the normalized conductance of IRK1. IRK1 could not permeate Zn 2+ because reverse potential was not changed. Three exponential fitting analysis indicates that time constant was not changed with the change of Zn 2+ concentration. The current result implicated that two mechanisms might be involved in the inhibitory effects of Zn 2+ : One was the result of surface charge, and the other was blocking actions of Zn 2+ at the surface site of IRK1. Howerver, the former was not likely to be the cause due to the failure of Zn 2+ in inhibition of IRK1 current at lower concentration, therefore, we concluded that the latter one was the likely mechanism underlying Zn 2+ blocking effects on IRK1 mediated current. CONCLUSION Zn 2+ is considered as a blocker of fast opening channel of IRK1 and its blocking site is at the surface of the channel.
出处
《第四军医大学学报》
北大核心
2002年第2期144-147,共4页
Journal of the Fourth Military Medical University
关键词
锌
钾通道
膜片钳术
卵母细胞
Zinc
potassium channels
patch clamp techniques
xenopus
oocytes
