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目的 :研究 Ba2 +对非洲爪蟾卵母细胞表达的双基因内向整流钾通道 (IRK1- T)的阻断作用。方法 :采用双微电极电压钳 (TEV)法。结果 :细胞外 Ba2 +浓度分别为 1,3,10和 10 0μmol/ L ,K+浓度为 90 mm ol/ L ,可见 Ba2 +的阻断作用对 IRK1- T的瞬间电流 (施加电压后 1m s)具有浓度依赖性、时间依赖性和电压依赖性 ;快速开通道阻断剂 Ba2 +对 IRK1- T的通道开关特性几乎无影响作用 ,IRK1- T对之不通透。三级指数拟合表明 :细胞外 Ba2 +低浓度(1和 3μm ol/ L )时 ,Ba2 +与 K+相互竞争同一结合位点 ,随着 Ba2 +浓度的增加 ,时间常数不增加但拟合的权数却浓度依赖性增加 ,所以失活过程随 Ba2 +浓度的增加越来越快 ;细胞外 Ba2 +高浓度 (10和 10 0μm ol/ L )时 ,时间常数随Ba2 +浓度的增加而减少 ,拟合的权数却浓度依赖性减少 ,失活过程也越来越快 ,说明 Ba2 +作用位点由通道的表面部位进入通道更深的地方。结论 :Ba2 +对 IRK1- T的阻断存在两种不同的机制
OBJECTIVE: To study the blocking effect of Ba2 + on the double-gene inward rectifier potassium channel (IRK1-T) expressed by Xenopus laevis oocytes. Methods: Double microelectrode voltage clamp (TEV) method. Results: The extracellular Ba2 + concentrations were 1, 3, 10 and 100 μmol / L, respectively, and the K + concentration was 90 mm ol / L. The blocking effect of Ba2 + on the transient current of IRK1- In a concentration-dependent, time-dependent and voltage-dependent manner. The fast open channel blocker Ba2 + has almost no effect on the channel switching characteristics of IRK1-T, but not IRK1-T. The three-level index fitting showed that Ba2 + and K + competed with each other for the same binding site at low concentrations of Ba2 + (1 and 3 μmol / L), and the time constant did not increase with the increase of Ba2 + concentration. However, But the concentration of Ba2 + increased with the increase of concentration, so the inactivation process became faster and faster with the increase of Ba2 + concentration. At high concentration of Ba2 + (10 and 100μmol / L), the time constant decreased with the increase of Ba2 + concentration , The fitting weights decreased in a concentration-dependent manner, and the inactivation process became faster and faster, indicating that the Ba2 + site was located deeper into the channel by the surface part of the channel. Conclusion: There are two different mechanisms for the blocking of IRK1-T by Ba2 +