Figure 4. Na⁺-HCO₃⁻ cotransport current in the absence of external Cl⁻.

A, steady-state currents, evoked by the same voltage protocol used in Fig. 3, recorded in the absence of extracellular Cl⁻, before and after 7 min of exposure of the myocyte to HCO₃⁻-containing solution. B, difference current obtained after subtracting the currents recorded in the absence of HCO₃⁻ from those recorded in its presence. The HCO₃⁻-sensitive current has similar characteristics to the current registered with Cl⁻-containing solutions.