Asymmetric voltage dependence of embryonic cardiac gap junction channels

Dependence of junctional conductance on voltage in some embryonic chick heart cells is asymmetrical due to the heterochannels formed by the proteins, connexins (Cxs), present at the junctional surfaces of the cells. Embryonic heart cells express three Cxs mRNA, which are immunolocalized at the junctional surface between cell pairs. The interactions between the Cxs form both homotypic ion channels with symmetric voltage dependence and heterotypic ion channels with asymmetric voltage dependence. The number of heterochannels in the junctions reduce with cardiac development.