Figure 4. Changes in pH_s, pH_i and E_m in a single EDL fibre in the absence and presence of 1 mm DIDS in HCO₃⁻-free, Hepes-buffered Ringer solution.

The muscle bundle was superfused with 15 mm Hepes-100% O₂-buffered Ringer solution in the absence of HCO₃⁻. Under these conditions DIDS led to a slow-down of dpH/dt and to a reduction of the amplitude (ΔpH) of both pH transients: during lactate uptake DIDS reduced dpH_s/dt from 0.09 to 0.05 ΔpH min⁻¹ and ΔpH_s from 0.049 to 0.024; during lactate release dpH_s/dt was reduced from 0.04 to 0.03 ΔpH min⁻¹ and ΔpH_s from 0.026 to 0.005 by DIDS. DIDS decreased dpH_i/dt from 0.082 to 0.077 ΔpH min⁻¹ during lactate uptake and from 0.065 to 0.046 ΔpH min⁻¹ during lactate release. In the absence of DIDS pH_i changed from 7.20 to 7.10 due to the uptake of lactic acid, but in the presence of DIDS pH_i changed only from 7.20 to 7.12. The resting potential was constant during the experiment.