Figure 6. Na⁺-HCO₃⁻ cotransport current in isolation.

Standard whole-cell configuration. A, steady-state currents, evoked by the same voltage protocol used in Fig. 3, recorded from a rat cardiac myocyte exposed successively to external Hepes, HCO₃⁻, and HCO₃⁻ in the presence of 0.1 mm SITS. External and internal K⁺, Cl⁻ and Ca²⁺ were replaced with Cs⁺, methanesulphonate and Mg²⁺, respectively. TTX, nifedipine and TEA were added to the extracellular solution. TEA was also included in the pipette solution. B, HCO₃⁻-sensitive difference current (HCO₃⁻ - Hepes) with a reversal potential of −101 mV.