[Quantitative connexin mRNA detection in posterior nodal extension of adult rat heart].
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 myocardium, whereas Cx43 mRNA level was about 25 times higher (P<0.05) in the working myocardium 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.


CONCLUSIONS
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.
Ou
Yan
Y
Department of Cardiology, Second Affiliated Hospital, Medical College of Xi'an Jiaotong University, Xi'an 710004, China. oy1114@163.com
Niu
Xiao-lin
XL
Han
Zhen-hua
ZH
Ren
Fu-xian
FX
Huang
Chen
C
D000818:Animals; D001283:Atrioventricular Node / Q000166:cytology / Q000378:metabolism; D018031:Connexin 43 / Q000235:genetics; D017630:Connexins / Q000235:genetics*; D005260:Female; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011690:Purkinje Fibers / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012849:Sinoatrial Node / Q000166:cytology / Q000378:metabolism; D000097003:Gap Junction alpha-5 Protein
D018031:Connexin 43; D017630:Connexins; D012333:RNA, Messenger; D000097003:Gap Junction alpha-5 Protein; C082920:connexin 45