Figure 2. Effects of pH_o on Orai1/STIM1 at various extracellular Ca²⁺ concentrations.

(A–D) Representative currents recorded at pH_o 5.5, 7.4 and 8.2 with extracellular Ca²⁺ concentrations of 0, 2, 20 and 120 mM. E, Averaged current amplitude measured at −100 mV at pH_o 5.5, 7.4, and 8.2 in various extracellular Ca²⁺ concentrations. Acidic pH_o 5.5 significantly inhibited current amplitude (p < 0.01; n = 8 ~ 17) and basic pH_o 8.2 remarkably potentiated current amplitude at each extracellular Ca²⁺ concentration (p < 0.01; n = 8 ~ 17). F, Normalized current amplitude at each Ca²⁺ concentration to the current amplitude at 2 mM Ca²⁺. G, Normalized Ca²⁺ current amplitude at each Ca²⁺ concentration to the Na⁺ current amplitude at 0 mM Ca²⁺. Analysis with two-way ANOVA indicated that the effects of pH_o 8.2 on Orai1/STIM1 was independent of extracellular Ca²⁺ concentration (F,G).