Using dual-voltage clamp technique we investigated gap junction gating properties of Cx40, Cx43 and Cx45 stably transfected HeLa cells and cultured neonatal rat cardiomyocytes.

Two synchronized switchclamp voltageclamp amplifiers (SEC05 NPI Electronic) were used with a common pulse protocol (pulseduration 2s, transjunctional voltage -120 to 120 mV).

In accordance to previously published data voltage gating of the Cx transfected HeLa cells was symmetric indicating homotypic gap junction channels. Gating sensitivity differed between the single Cx-Types (Cx45 > Cx40 > Cx43).

Data obtained from neonatal rat cardiomyocyte pairs expressing both Cx40 and Cx43 showed in some cases asymmetrical voltage gating and reduced voltage sensitivity which cannot explained by the presence of pure populations of homotypic gap junction channels of either isoform. In reference to Valiunas et al. (2001) we assume the additional presence of heterotypic and possibly even heteromeric gap junction channels in neonatal rat cardiomyocytes investigated in our laboratories.