【作者】 林吉进；

【导师】 李玉光；

【作者基本信息】 汕头大学 ， 心血管内科学， 2001， 硕士

【摘要】 背景及目的：心脏的间隙连接（gap junction，GJ）是指心肌细胞之间的连接通道，该通道具有亲水性、低选择性、低电阻等特点，其主要功能是完成心肌细胞之间的电化学信息交换，实现兴奋冲动在心脏的迅速传播。心室心肌细胞的间隙连接主要由连接蛋白43 （connexin 43，Cx43）构成，Cx43的正常表达与分布是心脏同步电活动和协调舒缩的重要保证。以往的研究表明慢性心肌缺血时心肌Cx43的大量降解和分布紊乱与心律失常的发生有密切关系，但急性心肌缺血时Cx43是如何改变，及其改变对心脏电生理特性有何影响，则至今尚未清楚。本实验旨在探明急性短时间（1～6小时）心肌缺血时心肌Cx43的改变及其对心脏电生理特性的影响。 方法：将20只犬随机分为对照组（4只）、1小时缺血组（6只）、3小时缺血组（5只）和6小时缺血组（5只）共4组；通过结扎左冠状动脉前降支分别造成0、1、3、6小时的左室前壁急性心肌缺血，将缺血心肌分为16个小区，应用48导联心电生理记录仪和带有56对电极的电极板分别测定各小区的传导速度，随后测定室颤阈值；取下心脏，将缺血心肌分为16小块，再将每小块分成心内膜下层、中间层、心外膜下层，应用激光共聚焦显微镜和双重标记的荧光免疫组织化学方法分别测定各层各小块缺血心肌Cx43含量和分布的改变；以Cx43象素密度代表Cx43的量，直线回归分析Cx43象素密度离散度、心肌传导速度离散度、室颤阈值三者之间的相关性。 结果：（1）急性心肌缺血时心肌Cx43已开始大量降解，缺血1小时约 汕头大学医学院硕士研究生毕业论文降解22．2见3小时约降解40卧6小时约降解5弧；o正常对照组心肌细胞端对端连接处CX43含量约为侧对侧连接处的1．37倍，缺血1小时后两者含量约相等，缺血6／J’时后，测对侧连接处CX43含量反而为端对端连接处的1．6倍；u）正常对照组心外膜下心肌各局部CX轮含量无明显差异，缺血后各局部CX43含量出现明显差异，缺血时间越长，差异越明显； K）正常对照组各层心肌细胞CX43含量差异无统计学意义，缺血后各层心肌CX“含量均下降，中间层CX43含量下降较其他两层更明显，差异有显著性意义；门）缺血前心肌传导速度离散度较小，缺血后传导速度离散度增大，并与Cx43象素密度离散度呈高度正相关，r＝0．9132；P＜0．01。（6）出现传导阻滞的区域其心肌CX43降解程度均超过70论问）CX43象素密度离散度与室颤阈值呈直线负相关，r刀．7833，P①．01；缺血区心肌传导速度离散度与室颤阈值呈直线负相关，r＝0．8602，P＜0·01。 结论：＊）急性短时间＊～6小时卜O肌缺血时 CX“已经开始大量降解；降解程度呈时间依赖性；①急性缺血时心肌细胞端对端连接处CX43降解速度较侧对侧连接处明显快，CX43 的分布模式发生明显改变；o）各局部，0肌CX43的降解程度不均一，可能与各局部心肌的缺血耐受性和侧支供血量不同有关；凹 急性缺血时中间层心肌CX43 降解速度最快，降解程度最大，可能与中间层心肌C的3较容易去磷酸化或对蛋白消化酶较敏感有关；闻局部心肌CX43 的严重降解将导致传导阻滞；似急性心肌缺血时CX好 的不均一降解是传导速度离散度增大、心脏电稳定性下降和心肌易损性增大的重要原因。更多还原

【Abstract】 Background & objective: The cardiac gap junction (GJ) is a channel connecting the neighbor myocytes, characterized by the hydrophilia, lower selectivity and lower resistance. The principal function of gap junction is to mediate the intercellular communication. Connexin 43(Cx43) is the predominant gap junction protein in the ventricular myocardium, the normality of expression and distribution of Cx43 is essential to the normal propagation of action potentials and the coordination of contraction in the heart. The previous studies have showed the decrease of expression and the alternation of distribution pattern of Cx43 correlated with the arrhythmia in the chronic ischemic heart. All the previous studies were carried out on chronic ischemic or hypoxic models, and no study has focused on the acute effects of ischemic on gap junction channel changes. The purpose of this study was to investigate changes of Cx43 and its electrophysiologic effects following short time period (1 to 6 hours) of ischemia. Methods: Studies were carried out in 20 mongrel dog canine which were randomly divided into control group(nM), 1 hour ischemia group (n%), 3 hours ischemia group (n~5) and 6 hours group (n~5). The acute myocardial ischemia was induced by ligation of the left anterior descending coronary artery. Ischemic myocardium was divided into 16 small regions. The conduction velocity of each small region was detected with a electrode array including 56 pairs of electrodes 3 before and after ischemia, and ventricular fibrillation threshold (VET) was detected at last. After detecting of VET the ischemic myocardium was harvested, the ischemic myocardium was divides into 16 lX 1cm2 segments, and each segment was divided into the endo條ayer, middle layer and epi條ayer. The expression and distribution of Cx43 of each segment was studied by laser confocal microscopy with a double條abel immunohistochemistry technique. The correlation among dispersion of Cx43 pixel density, dispersion of conduction velocity and VFT was analysed through the linear regression. Result: (l)The Cx43 degraded rapidly during acute myocardiacl ischemia. There was a 22.2% decrease following 1 hour of ischemia, a 40% decrease following 3 hours of ischemia, and a 54% decrease following 6 hours of ischemia. (2)The Cx43 pixel density at end梩o梕nd junction areas was 1. 37 folds of that at side梩o梥ide junction areas in the control group, on the contrary, the Cx43 pixel density at side梩o梥ide junction areas was 1. 6 folds of that at end梩o梕nd junction areas following 6 hours of ischemia. (3)In control group, there was not significant difference among the Cx43 pixel density of each segment, and the difference became significant following ischemia. (4) There was not significant difference among the Cx43 pixel density of each myocardial layer in control group, the decrease of Cx43 was more significant in the middle layer of myocardium in all the ischemia group. (5) The disn~rcion of conduction velocity before 4 ischemia was small, and increasing following ischernia. There was a significant correlation between the dispersion of Cx43 pixel density and the dispersion of conduction velocity, r~0.9132, P<0. 01. (6)The更多还原