Junctional delay, frequency, and direction-dependent uncoupling of human heterotypic Cx45/Cx43 gap junction channels.

Gap junction (GJ) channels form low resistance passages between cardiomyocytes and play a role in the rapid propagation of action potentials in the heart. A GJ channel is formed by two properly docked hemichannels and each hemichannel is a hexamer of connexins. Connexin40 (Cx40) and Cx43 are the dominant connexins in atrial myocytes, while Cx45 is mostly expressed in the sinoatrial (SA) and atrioventricular (AV) nodes which directly connect nodal cells with atrial myocytes, possibly via heterotypic Cx40/Cx45 and/or Cx43/Cx45 GJs.