大蒜素对兔心房肌细胞超速激活延迟整流钾电流的作用

Effects of allitridum on ultra rapid delayed rectifier potassium current in rabbit atrial cardiomyocytes

目的研究大蒜素对兔单个心房肌细胞超速激活的延迟整流钾电流（I_KUr）的作用，探讨其抗房性心律失常的机制。方法采用双酶法分离兔单个心房肌细胞，应用细胞外局部灌流法给药，采用全细胞膜片钳技术记录电流，以观察大蒜素对kUr的作用。结果大蒜素200gmol／L对正常兔心房肌细胞I_KUr有显著的抑制效应，使I_KUr峰值由（14．5±3．2）pA／pF降至（7．9±1．2）pA／pF（P〈0．01，n=15）。大蒜素可使I_KUr的电流．电压曲线降低，且随着除极化电位的增加，作用更加明显，提示其作用具有电压依赖性。同时，发现大蒜素对I_KUr的抑制效应存在浓度依赖性，半数抑制浓度（IC50）为149．6μmol／L。门控动力学机制研究发现，大蒜素可以使通道激活曲线右移，延迟激活；使通道稳态失活左移，加速失活；使通道失活后恢复时间延长，减缓通道失活后的再次激活。从不同环节减少，I_KUr通道的开放，降低电流密度。结论大蒜素抑制心房肌细胞膜上I_KUr，这可能是其治疗房性心律失常的细胞电生理基础。

Objective To determine the effect of allitridum on the ultra rapid delayed rectifier potassium current （I_KUr） in single rabbit atrial cardiomyocyte, and investigate the mechanism of its anti-atrial arrhythmia. Methods The dual enzymatic method was used to separate single rabbit atrial cardiomyocyte. The drug was applied via extracellular supserfusion, and current was evoked and recorded using Axon MultiClamp 700B amplifier. Results Allitridum at 200gmol/L exerted obvious inhibitory effect on I_KUr in normal rabbit atrial cardiomyocyte, and decreased the peak value from （14.5 ± 3.2） to （7.9 ± 1.2）pA/pF （P 〈 0.01, n = 15）. Allitridum also resulted in a decrease in current-voltage curve, and the effect became more significant with the increase of depolarization potential, in a voltage-dependent manner. Allitridum also showed the inhibitory effect on/KUr in a dose-dependent manner, with its IC50 value of 149.6μmol/L. Allitridum caused a significant positive shift of the steady-state activation curve of I_KUr, and then delayed the activation, while a markedly negative shift of the steady-state inactivation of I_KUr, and so accelerated the inactivation. Furthermore, the drug markedly lengthened the time constants for I_KUr recovery from inactivation, and decelerated the re-inactivation after inactivation. It decreased the channel open at many links, and reduced current density. Conclusion Allitridum derived from Chinese herb, garlic bulb, potently blocks I_KUr, which might be the underlying cellular electrophysiological mechanism of its therapeutic effect on atrial arrhythmia.