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目的：研究人的心房肌细胞瞬间外向钾电流（Ｉｔｏ）的特性．方法：采用膜片箝全细胞记录法观察人心房肌通道电流的变化，在用ＣｄＣｌ２０１ｍｍｏｌ·Ｌ－１阻断钙电流的情况下，细胞膜去极化引出瞬间外向钾电流（Ｉｔｏ）．结果：Ｉｔｏ为电压依赖的电流，迅速激活，迅速失活．４ＡＰ（４氨基吡啶）１０ｍｍｏｌ·Ｌ－１（选择性的Ｉｔｏ的阻断剂）能完全阻断此电流．其ＩＣ５０值为０６７ｍｍｏｌ·Ｌ－１．４ＡＰ１ｍｍｏｌ·Ｌ－１能使Ｉｔｏ的激活曲线明显向正电位移动，使Ｉｔｏ的激活电压提高，且较难激活Ｉｔｏ．结论：在人心房肌细胞，Ｉｔｏ是一种主要的钾电流，它可被４ＡＰ阻断
Objective: To study the transient outward potassium current (Ito) of human atrial myocytes. Methods: Whole-cell patch-clamp recording was used to observe the changes of atrial currents in human atrial myocardium. When CdCl20.1 mmol·L-1 was used to block the calcium current, the depolarization of the plasma membrane led to transient outward potassium current (Ito). Results: Ito is a voltage-dependent current, rapidly activated, rapidly inactivated. 4 AP (4 aminopyridine) 10mmol · L-1 (selective Ito blockers) can completely block the current. The IC50 value of 0.67mmol · L-1.4AP1mmol · L-1 can make Ito activation curve significantly shifted to the positive potential, Ito activation voltage increased, and more difficult to activate Ito. Conclusion: In human atrial myocytes, Ito is a major potassium current that can be blocked by 4AP