pHi changes in response to exposure to ammonia in uninjected and in AQP4-expressing oocytes.
A, transport of ammonia as either NH4+ or NH3. If NH4+ crosses the cell membrane, it will cause an intracellular acidification, whereas influx of NH3 will cause an intracellular alkalization. B and D, pHi traces from an uninjected oocyte (B) and from two AQP4-expressing oocytes (D) exposed to 10 mm NH4Cl (marked with a black bar). C, overview of the individual pHi changes in uninjected oocytes after 15 min of exposure to 10 mm NH4Cl, summarized in the inset, n = 15. E, overview of the individual pHi changes in AQP4-expressing oocytes after 15 min of exposure to 10 mm NH4Cl, summarized in the inset, n = 33. F, overview of the NH4Cl-induced ΔpHi in uninjected (Uninj.) oocytes (n = 15) and AQP4-expressing oocytes (n = 33). Statistical significance was determined with paired Student's t test (unpaired Student's t test in panel F). ***, p < 0.001; ns, not significant.