Fig. 1.

Extracellular pH (pH_e)-dependence of membrane potential (V_m) and intracellular pH (pH_i) in H₂O-injected and mSlc4a11-expressing oocytes. A and B: pH_i and V_m of an oocyte that had been injected with H₂O (A) or mSlc4a11 cRNA (B) was monitored while the cell was exposed to extracellular solutions of pH 6.5, 7.5, or 8.5. The gray dashed boxes exemplify the periods over which the rates of [H⁺] change were calculated for C (i.e., omitting rapid changes close to the time of solution change that could be associated with artifacts or other non-Slc4a11-dependent phenomena). The arrow in B shows an enhanced depolarization of cells in pH_e = 6.5 solution following exposure to pH_e = 8.5 solution. C: the rate of change of intracellular [H⁺] during exposure to pH_e = 6.5, 7.5, or 8.5 solutions (n = 6). Rates were calculated from the change in [H⁺] that occurred during the periods such as enclosed by gray boxes in A and B. The letters above each bar denote statistically indistinguishable groups reported by general linear model with Tukey's post hoc analysis (confidence interval 95%). D and E: average V_m of H₂O-injected (D) or mSlc4a11-expressing (E) cells during exposure to pH_e = 6.5, 7.5, or 8.5 solutions (gray data points), with letters to denote statistically indistinguishable groups. V_m values were taken at the end of the exposure period to each solution. For each value of pH_e, each “n” represents an averaged value from the 2–3 exposure periods to which each cell was subjected. The white data points indicate the equilibrium potential for H⁺ determined at the average pH_i from A or B at each value of pH_e. Note that standard error bars are included but are eclipsed by the data point markers.