Fig. 5.

Gap19 inhibits hemichannel unitary currents in ventricular cardiomyocytes. a Whole-cell recording performed in acutely isolated ventricular cardiomyocytes revealed a V_m dependent activation of Cx43 hemichannels (30 s voltage steps—traces representative for seven similar recordings). The all-point histogram illustration below the traces indicates a ~200 pS unitary conductance at V_m = +30 mV. In the presence of Gap19 (100 μM in the pipette), V_m steps to more positive potentials were necessary (traces representative for six similar recordings). b Example traces illustrating that unitary current activities was still present after repolarizing to −70 mV. The all-point histogram below indicates a ~200 pS unitary conductance of the unitary tail current events. c I_m − V_m plot of open hemichannels demonstrating a reversal potential of ~0 mV and a single-channel slope conductance of ~196 pS. d Voltage dependent activation of hemichannels, demonstrating that Gap19 (100 μM) shifted the activation curve to more positive potentials. The quantity Q_m/V_m was calculated by dividing the integrated unitary current activity by the corresponding V_m, and represents the integrated single-channel conductance over the 30 s voltage steps (n = 6). e Gap19 inhibition of unitary events did not influence the open hemichannel I_m − V_m plot (~0 mV reversal potential and 204 pS single-channel slope conductance, not different from control). f Example traces recorded in a cardiomyocyte before and after exposure to MI (5 μM FCCP and 1 mM IAA). Voltage steps from −70 mV (5 s) to +40 mV (30 s) were repetitively applied. Unitary current activity was completely absent with Gap19 in the recording pipette. g Summary graph illustrating progressively increasing unitary current activity after application of MI (n = 4). Stars indicate statistical significance compared to baseline before MI induction. Recordings with Gap19 in the pipette were flat, lacking any unitary activity, also after MI induction (filled squares on the abcis). Gap19 completely suppressed MI-promoted hemichannel activity. Number signs indicate statistical significance compared to the corresponding open squares recorded without Gap19 in the pipette