Figure 8.

Effects of external HCO₃⁻ on steady-state currents, perforated whole-cell configuration A, steady-state currents evoked by 8 s-duration voltage-clamp ramps ranging from −130 to +30 mV, from a holding potential of −75 mV, recorded from a cardiomyocyte exposed successively to external Hepes, HCO₃⁻ (10 min), and HCO₃⁻ in the presence of SITS (10 min). B, HCO₃⁻-sensitive difference current (HCO₃⁻− Hepes) and SITS-sensitive difference current (HCO₃⁻− (HCO₃⁻+ SITS). C, average current–voltage relationship for the HCO₃⁻-sensitive difference current (HCO₃⁻− Hepes) (n = 7) and SITS-sensitive difference current (HCO₃⁻− (HCO₃⁻+ SITS) (n = 7). These two difference currents reversed at ∼−85 mV, a value close to the expected E_NBC of an electrogenic NBC with a stoichiometry ratio of 2HCO₃⁻: 1Na⁺.