Fig. 2

Intracellular pH (pH_i) changes induced by ionomycin (IM) in the absence of HCO₃ ⁻. a 5 μM IM in HCO₃ ⁻-free solution. IM (5 μM) induced no change in pH_i in Ca²⁺-free solution. The re-introduction of Ca²⁺ induced a rapid pH_i decrease followed by a gradual pH_i increase. b 1 μM IM in HCO₃ ⁻-free solution. When control solution was switched to HCO₃ ⁻-free solution, pH_i transiently increased from 7.4 to 7.7 and then plateaued (pH_i 7.5). The switch to Ca²⁺-free solution and addition of IM (1 μM) did not change pH_i. The re-introduction of Ca²⁺ induced a rapid pH_i decrease without any pH_i increase