大鼠心脏结后延伸连接蛋白转录表达的定量研究

Quantitative connexin mRNA detection in posterior nodal extension of adult rat heart

目的探讨结后延伸连接蛋白40(Cx40)、连接蛋白43(Cx43)和连接蛋白45(Cx45)的表达与房室结折返性心动过速的关系。方法采用激光捕获仪精确分离大鼠心脏结后延伸及其房室结、窦房结、浦肯野纤维和右房肌、右室肌。通过实时荧光聚合酶链反应对3种Cx表达进行定量分析。结果激光捕获成功分离了结后延伸及其他传导细胞和工作肌细胞。Cx在心脏不同区域表达有一定的特异性,但又有明显的分布交叉性。结后延伸Cx表达模式与房室结、窦房结较相近,而和浦肯野纤维、工作肌细胞明显不同。在结后延伸,具有细胞高电导特性的Cx43表达量比工作肌显著减少约25倍(P<0.05),比浦肯野纤维减少约18倍(P<0.05);具有更高电导特性的Cx40显著低于浦肯野纤维,大约减少6.8倍(P<0.01);而具有低电导的Cx45比工作肌相对高表达。结论由于结后延伸相对高表达高阻抗的Cx45,少量表达低阻抗的Cx43和Cx40,使冲动在结后延伸缓慢传导,为房室结折返环路的慢径形成提供了物质基础;折返环路不仅涉及致密结,而且还涉及心房和结后延伸,结后延伸、房室结和心房Cx表达水平即电偶联的强度各异,形成了细胞连接处阻抗的不连续,当在一定条件下有可能形成单向阻滞,导致折返性心律失常的发生。

Objective To quantitatively detect the expression of connexins （Cx） mRNA in the posterior nodal extension （PNE） of adult rat heart and understand the relationship between Cx expression and atrial ventricular nodal reentrant tachycardia , （AVNRT）. Methods PNE was separated from adult rat heart by means of laser microdissection （LCM）, and the cells were also isolated from the atrioventricular node （AVN）, sinoatrial node （SAN）, Purkinje fiber （PF）, right atrium （RA） and right ventricle （RV）, to serve as the controls. The Cx mRNA level was detected in these cells with quantitative real-time PCR （QRT-PCR）. Results The cells were successfully isolated from the PNE and other regions of adult rat heart, where heterogeneous expression of the 3 Cx isoforms （Cx43, Cx45, and Cx40） were observed. Cx45 mRNA showed higher expression in the PNE than in the working myoeardium, whereas Cx43 mRNA level was about 25 times higher （P〈0.05） in the working myoeardium and 18 times higher （P〈0.05） in the PF than in the PNE. In the PF, Cx40 mRNA level was proximately 6.8 times （P〈0.01） as much as that in the PNE. Cx expression in the PNE was, however, similar to that in the SAN and AVN. Conclusion Cx mRNAs exhibit heterogeneous expression in the PNE to allow the formation of the slow pathway. In addition, Cx expression in the PNE is very different from that in the adjacent myocardium, resulting in conduction discontinuity at the cellular junction, where, on certain occasion, unidirectional block may occur to cause AVNRT.