Functional and molecular mechanism of intracellular pH regulation in human inducible pluripotent stem cells

Figure 6 The change in the activity of the Na⁺/H⁺ exchanger and the Na⁺/HCO₃^- cotransporter and the resting pH_i during the loss of pluripotency in human induced pluripotent stem cells. A: The traces showed the changes in pH_i recovery after NH₄Cl prepulse-induced intracellular acidification in E8 medium (containing fibroblast growth factor 2, FGF2, and transforming growth factor β1, TGFβ1) and E6 medium (without FGF2 and TGFβ1) for 1 to 4 d (E6-1d to E6-4d) in HEPES-buffered solution; B: The charts showed the pH_i recovery rate in E6-1d to -4d normalized to the rate in E8 (% of E8) in HEPES-buffered solution, which was estimated at pH_i = 6.9 and 7.2, respectively, and averaged for 3 experiments similar to that shown in A; C: The max/min plots showed the resting pH_i in E8, E6-1d, E6-2d, E6-3d and E6-4d media that were averaged from similar experiments shown in A (n = 5-20); D: The traces showed the changes in pH_i recovery after NH₄Cl prepulse-induced intracellular acidification in E8 and E6-1d to E6-4d media in 5% CO₂/HCO₃^--buffered solution; E: The graphs show the pH_i recovery rate in E6-1d to E6-4d normalized to the rate in E8 (control) in 5% CO₂/HCO₃^--buffered solution, which was estimated at pH_i = 6.9, 7.2 and 7.5, respectively, and averaged for 3 experiments similar to that shown in D; F: The max/min plots showed the resting pH_i in E8 E6-1d, E6-2d, E6-3d and E6-4d media, averaged from similar experiments shown in D (n = 5-20). Error bars represent the mean ± SE. The histograms in C and F show the mean and min to max values. NS: No significant difference; hiPSCs: Human induced pluripotent stem cells.