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目的和方法 :采用双微电极电压钳 (TEV)法研究细胞外Mn2 +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。结果 :细胞外Mn2 +浓度分别为 0、1.2 5、2 .5、5、10和 2 0mmol/L ,K+浓度为 90mmol/L ,可见Mn2 +对IRK1的瞬间电流 (施加电压后 2ms)具有Mn2 +浓度依赖性和电压依赖性阻断作用 ;细胞外加Mn2 +后反转电位没有变化 ,因而IRK1对之不通透。细胞外Mn2 +浓度较低时 ,抑制作用的效力比Mn2 +浓度较高时强 ;细胞外K+浓度为 90mmol/L和Ba2 +浓度为 30 μmol/L时 ,Mn2 +可竞争性与Ba2 +争夺结合位点 ,随着Mn2 +浓度增加 ,电流失活过程逐渐减缓 ,电场距离分数由 0 .45逐渐变小至 0 .2 8,Ba2 +在通道中的结合位点也逐渐离开通道 ,说明多离子通道IRKl中具有多离于阻断形式 ,同时也表明Mn2 +与Ba2 +。都是IRKl的一种快速开通道阻断剂。结论 :细胞外Mn2 +对IRK1的抑制作用通过了表面电荷机制和快速开通道阻断
PURPOSE AND METHODS: The blocking effect of extracellular Mn2 + on the inward rectifier potassium channel (IRK1) expressed by Xenopus laevis oocytes was studied by double microelectrode voltage clamp (TEV). Results: The extracellular concentrations of Mn2 + were 0,1.25,2.5,5,10 and 20 mmol / L, respectively. The K + concentration was 90 mmol / L. The transient current of Mn2 + to IRK1 (2ms after voltage application) + Concentration-dependent and voltage-dependent blocking; the reversal potential did not change after addition of Mn2 +, so IRK1 was not transparent. When the concentration of extracellular Mn2 + was lower, the inhibitory effect was stronger than that of Mn2 +. When the extracellular K + concentration was 90mmol / L and the concentration of Ba2 + was 30μmol / L, Mn2 + could compete with Ba2 + As the concentration of Mn2 + increased, the deactivation of the current gradually slowed down and the distance fraction of the electric field gradually decreased from 0.45 to 0.28. The binding sites of Ba2 + in the channel also gradually departed from the channel, indicating that more Ion channel IRKl in a more isolated blocking form, but also that Mn2 + and Ba2 +. Are a fast IRKl open channel blockers. Conclusion: The inhibitory effect of extracellular Mn2 + on IRK1 through surface charge mechanism and rapid open channel blockade