犬右室瞬间外向钾电流异质性的研究

应用全细胞钳制技术对犬右室心外膜下 (epi)细胞、中层 (M)细胞和心内膜下 (endo)细胞复极 1期瞬间外向钾电流 (Ito1)的强度、密度和动力学过程进行系统定量研究 ,以期从复极 1期主要离子流的角度 ,探讨右室复极 1期跨越室壁的电异质性。结果发现 :犬右室epi细胞和M细胞存在强大的Ito1离子流 ,在刺激频率为 0 .2Hz、37℃和去极化试验电压为 +70mV时 ,epi细胞和M细胞峰值Ito1离子流的强度分别为 46 5 0± 176 0 ,36 2 0± 1880pA ,其激活和失活动力学过程符合Boltzmann分布。与epi细胞和M细胞相比 ,endo细胞Ito1离子流微小 ,同样条件下其平均峰值Ito1离子流仅为 480± 130pA。表明在右室跨越室壁的三层细胞间 ,特别是epi细胞与endo细胞之间、M细胞与endo细胞之间 ,复极 1期存在明显的Ito1离子流强度差异和强大的Ito1离子流梯度 ,此为右室电异质性的一种突出表现 ,它可能是Brugada综合征等疾病所致恶性心律失常的重要离子基础之一

Study on Electrical Heterogeneity of the Right Ventricular Transient Outward Potassium Current

In this study,by using of whole cell patch clamp technique,we quantitatively studied on the 4 aminopyridine sensitive and calcium independent transient outward potassium current (Ito 1) in repolarization phrase 1 of canine right ventricular epicardial cells,midcardial cells(M cells) and endocardial cells,in order that we could systemically probe into the transmural electrical heterogeneity of the right ventricle in repolarization phrase 1 from the viewpoint of Ito 1.Our result showed at +70mV depolarizing test potential and 37 ℃,the average peak Ito 1 of epicardial cells and M cells were approximately 4 650±1760,3 620±1 880 pA respectively.The activated and inactivated kinetic process of epicardial cells and M cells were in accordance with Boltzmann distribution.Compared with the Ito 1 of epicardial cells and M cells,the average peak Ito 1 of endocardial cells was very small or tiny,which was only about 480±130 pA.These results suggest there exists evident difference of Ito 1 among the three type cells,especially between epicardial cells and endocardial cells,M cells and endocardial cells in the right ventricle.This difference is one of the prominent manifestations of the right ventricular electrical heterogeneity and may be one of the important ionic bases of some malarrhythmias caused by Bragada syndrome etc.