兔界嵴细胞离子通道特性研究

目的研究生理状态下及异丙肾上腺素灌流对兔界嵴(CT)与梳状肌(PM)细胞动作电位(AP)及钠电流(INa)、短暂外向钾电流(Ito)、L型钙电流(ICa-L)、延迟整流钾电流(IK)及内向整流性钾电流(IK1)的影响,探讨CT与房性心律失常的关系。方法酶解法分离兔CT及PM细胞,利用全细胞膜片钳技术,记录生理状态下及异丙肾上腺素灌流后CT与PM细胞AP及INa、Ito、ICa-L、IK及IK1的变化。结果①生理状态下,CT细胞动作电位时程(APD)较长,可见明显的平台期;PM细胞AP形态与普通心房肌细胞相似,1期复极迅速,平台期短,类似三角形。②生理状态下,CT细胞Ito电流密度比PM细胞明显降低(7.13±0.38 pA/pF vs 10.70±0.62 pA/pF,n=9,P<0.01),而INa、Ito、ICa-L、IK及IK1则无明显差别。③异丙肾上腺素灌流时CT与PM细胞APD20、APD50、APD90均延长(n=8,P<0.01);指令电位+50 mV时,CT与PM细胞Ito电流密度均减少(n=9,P<0.01)而IK均增加(n=8,P<0.05);指令电位+10 mV时,CT与PM细胞ICa-L电流密度均增加(n=9,P<0.01);IK1在两种心肌细胞均无明显差异。结论 CT与PM细胞AP差异与Ito有关。异丙肾上腺素灌流时ICa-L与IK增强,Ito抑制使CT与PM细胞APD延长,触发机制可能是CT参与房性心律失常的机制之一。

Ion channels characteristics of crista terminalis cells in rabbits

Objective To investigate the action potential(AP) and sodium currents(INa),transient outward potassium current(Ito),L-type calcium current(ICa-L),the delayed rectifier potassium current(IK) and inward rectifier potassium current(IK1) of both crista terminalis(CT) and pectinate muscles(PM) cells on the physiological state in rabbits and the effects of isoproterenol perfusion in order to explore the relationship between CT and atrial tachycardia.Methods The CT and PM cells were obtained by enzymatic dissociation,then AP and INa,Ito,ICa-L,IK,IK1 were recorded via whole-cell patch-clamp technique both on the physiological state and after isoproterenol perfusion.Results ①On the physiological state,the action potential duration(APD) of CT cells was long and showing a clear plateau;AP configuration of PM cells was similar to that of regular atrial myocytes,phase I repolarization was rapid,and the plateau was short and triangle-like.②Under physiological conditions,Ito current density of CT cells was significantly lower than PM cells(7.13±0.38 pA/pF vs 10.70±0.62 pA/pF,n=9,P<0.01),while INa,Ito,ICa-L,IK and IK1 current density had no significantly difference between them.③After isoproterenol perfusion,20%,50% and 90% duration of action potentials(APD20,APD50 and APD90) were prolonged in both CT cells and PM cells(n=8,P<0.01).When the command potential at +50 mV,Ito current density was reduced(n= 9,P<0.01) while the IK current densitywas increased(n=8,P<0.05) both in CT cells and PM cells;When the command potential at+10 mV,ICa-L current density was increased(n= 9,P<0.01) while the IK1 had no significantly difference(n=8,P<0.05) in them.Conclusion The difference of AP is related with Ito in CT and PM cells.ICa-L and IK enhance while Ito inhibition after isoproterenol perfusion,which results in APD prolonged,thus trigger mechanism in CT may be involved in one of the mechanisms of atrial arrhythmia.