Electrical Propagation in Synthetic Ventricular Myocyte Strands From Germline Connexin43 Knockout Mice

To characterize the role of connexin43 (Cx43) as a determinant of cardiac propagation, we synthesized strands and pairs of ventricular myocytes from germline Cx43−/− mice. The amount of Cx43, Cx45, and Cx40 in gap junctions was analyzed by immunohistochemistry and confocal microscopy. Intercellular electrical conductance, gj, was measured by the dual-voltage clamp technique (DVC), and electrical propagation was assessed by multisite optical mapping of transmembrane potential using a voltage-sensitive dye. Compared with wild-type (Cx43+/+) strands, immunoreactive signal for Cx43 was reduced by 46% in Cx43+/− strands and was absent in Cx43−/− strands. Cx45 signal was reduced by 46% in Cx43+/− strands and to the limit of detection in Cx43−/− strands, but total Cx45 protein levels measured in immunoblots of whole cell homogenates were equivalent in all genotypes. Cx40 was detected in ≈ 2% of myocytes. Intercellular conductance, gj, was reduced by 32% in Cx43+/− cell pairs and by 96% in Cx43−/− cell pairs. The...