Figure 3. Activating sarcolemmal acid efflux and influx.

A, Hepes-buffered solution (pH_o 7.40). Ratiometric recording of pH_i. A 10 mM ammonium prepulse was succeeded by a 40 mM acetate prepulse. Hoe 694 (30 μM) was added, as indicated by bar, to inhibit Na⁺-H⁺ exchange. B, 5 % CO₂/HCO₃⁻-buffered solution (pH_o 7.40). The first bar above the pH trace indicates application of 10 mM ammonium chloride. The second bar indicates application of 80 mM acetate. Shortly before removal of the acetate, Na⁺_o was withdrawn (replaced by NMDG), in order to inhibit acid extrusion on Na⁺-H⁺ exchange and Na⁺-HCO₃⁻ cotransport.