A cellular suspension from rat submandibular glands was exposed to different concentrations of NH4Cl, and the variations of the intracellular concentration of calcium ([Ca2+] i) and the intracellular pH (pHi) were measured using fura‐2 and 2′, 7′‐bis‐(2‐carboxy‐ethyl)‐5 (6)‐carboxyfluorescein. More than 5 mmol/l NH4Cl significantly increased the [Ca2+] i without affecting the response to 100 µmol/l carbachol. When exposed to 1 and 5 mmol/l NH4Cl, the cells acidified immediately. At 30 mmol/l, NH4Cl first alkalinized the cells and the pHi subsequently dropped. This drop reflects the uptake of NH ions that dissociate to NH3 and H+ in the cytosol. These protons are exchanged for extracellular sodium by the Na+/H+ exchanger because the presence of an inhibitor of the exchanger in the medium increased the acidification induced by 1 mmol/l NH4Cl. Ouabain partly …