Connexins and ion channel expression in node like tissues

AIM To study the histological features of node-like tissues,examine connexins and ion channels expression in the node like tissue,and demonstrate its potential electrophysiological significance in heart conduction. METHODS Adult SD rats (n=6) were used. Serial sections from the entire AVN conduction system to the AV junction were obtained. Masson's trichrome stain was performed on AVN regions to assess fibrous tissue. Three connexins proteins (Cx) including Cx43,Cx40 and Cx45, which dominate the electrotonic conduction of the heart and three main ion channels (Nav1.5,Cav3.1 and HCN4) participating in the depolarization of myocardial cell were immunohistochemically labeled. RESULTS Masson's trichrome stain and immunohistochemical label revealed that retroaortic node (RAN),like compact node (CN) and inferior nodal extensions (INE) had statistically significant higher expression of connexin isoforms and ion channels (including Cx45, Cav3.1 and HCN4) and lower expression of Cx43, Cx40 and Nav1.5). CONCLUSION RAN possesses electrotonic level and action potential level of connexin isoforms and ion channels similar to those of AVN and INE. RAN may have the same conduction properties as INE and could act as an ectopic pacemakers and a source of tachycardia.