炙甘草汤对大鼠心房肌细胞L型钙电流及其动力学特征的影响

Effects of Zhigancao Decoction on L-type Calcium Current and Kinetics Characteristics of Atrial Myocytes in Rats

目的:研究炙甘草汤对大鼠心房肌细胞L型钙电流(I_(Ca-L))及其动力学特征的影响。方法:选取24只大鼠随机分为空白对照组和炙甘草汤低剂量组(1.125 g/mL)、中剂量组(2.25 g/mL)、高剂量组(4.5 g/mL),每组6只。3组药物组大鼠分别按各自浓度给予相同体积的炙甘草汤药液灌胃,对照组大鼠予以等体积生理盐水灌胃。给药1周后利用酶解法对4组大鼠心房肌细胞进行急性分离,用全细胞膜片钳技术记录4组心房肌细胞I_(Ca-L)并比较I-V曲线,选取中剂量组与对照组的心房肌细胞比较I_(Ca-L)通道的动力学特征。结果:与对照组比较,炙甘草汤低、中、高剂量组的大鼠心房肌细胞I_(Ca-L)均发生不同程度的抑制效果,I-V曲线均上移。观察比较中剂量药物组与对照组的I_(Ca-L)通道动力学特征,发现2组细胞的激活曲线和半数激活电压,差异无统计学意义(P>0.05),但中剂量药物组细胞的稳态失活曲线发生向右偏移,半数失活电压V_(1/2)升高(P<0.05),失活后恢复曲线向下偏移,时间常数(τ)延长(P<0.01)。结论:炙甘草汤能够抑制大鼠心房肌细胞L型钙电流,减慢心房细胞钙通道失活速度,延长失活后恢复的时间,从而起到减慢心率的作用,这可能是炙甘草汤临床上治疗房性心律失常的作用机制。

Objective:To investigate the effects of Zhigancao Decoction on L-type calcium current(I_(Ca-L))and the kinetics characteristics of atrial myocytes in rats.Methods:Twenty-four rats were randomly divided into a control group and low-dose(1.125 g/mL),medium-dose(2.25 g/mL),and high-dose(4.5 g/mL)Zhigancao Decoction groups,with six rats in each group.The rats in the Zhigancao Decoction groups were treated correspondingly by gavage,and those in the control group received an equal volume of normal saline.One week after the administration,atrial myocytes in the four groups were acutely isolated by enzymatic hydrolysis.The I_(Ca-L) of atrial myocytes in the four groups was recorded by the whole-cell patch clamp technique and the I-V curves were compared.The kinetics characteristics of I_(Ca-L) channels of atrial myocytes were compared between the medium-dose Zhigancao Decoction group and the control group.Results:Compared with the control group,the Zhigancao Decoction groups showed inhibited I_(Ca-L) of atrial myocytes and upward-shifted I-V curves.As revealed by the comparison of kinetics characteristics of I_(Ca-L) channels between the medium-dose Zhigancao Decoction group and the control group,the differences in the activation curve and half activation voltage of cells between the two groups were not significant(P>0.05),but in the middle-dose Zhigancao Decoction group,the homeostatic inactivation curve shifted to the right,and the half-deactivation voltage V_(1/2) was increased(P<0.05).Additionally,the curve of recovery after inactivation shifted downward,and the time constant(τ)was prolonged(P<0.01).Conclusion:Zhigancao Decoction can inhibit the I_(Ca-L) of atrial myocytes in rats,delay the inactivation speed of calcium channels in atrial myocytes,and prolong the recovery time after inactivation,thereby achieving the effect of slowing down the heart rate.It may be the mechanism of Zhigancao Decoction in the clinical treatment of atrial arrhythmia.