Fig. 2. HERG channel activity contributes to the resting potential of fusion-competent myoblasts. (A) Resting membrane potential of fusion-competent myoblasts before and after application of 5 µM dofetilide. (B) Examples of dofetilide-sensitive (5 µM) K⁺ currents recorded in a proliferating myoblast overexpressing HERG. The voltage was held steadily at -4 mV and stepped every 15 s to various potentials ranging from -84 mV to +36 mV for 9 seconds. (C) Peak (triangles) and steady-state (circles) HERG current plotted as a function of the voltage steps. Currents were considered at steady-state after 9 seconds. The reversal potential for K⁺ ions (E_K), the mean resting potential of fusion competent-myoblasts in control conditions (Rp) and the mean resting potential of fusion competent-myoblasts in presence of 5 µM dofetilide (dof) are indicated. The reversal potential of the recorded current was shifted by -4 mV to adjust it to E_K (-80 mV; [K⁺]_out=5 mM). Smaller plot shows the peak (triangles) and steady-state (circles) HERG conductance-to-voltage relationships. A reversal potential of -80 mV (E_K) was used to calculate conductance.