Na/H exchange in antral cells isolated from Necturus, rabbit, and guinea pig

Mechanisms of intracellular pH (pHi) regulation were investigated using the pH-sensitive dye BCECF (2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein) to measure pHi in isolated antral cells from Necturus, rabbit, and guinea pig. The BCECF fluorescence was calibrated in terms of pHi by using a nigericin-high potassium concentration method to equilibrate pHi and pHo. Average pHi for the cells of Necturus and rabbit was approximately 7.1 in a HEPES-buffered, HCO3-free Ringer's solution. Average pHi in Necturus cells in CO2/HCO3-buffered Ringer's solution was approximately 7.0. An ammonium-loading technique was used to acidify the cell to measure intrinsic buffering capacity (beta i) and to monitor pHi recovery. Average beta i = 28 mM per pH unit in Necturus and 42 mM per pH unit in rabbit cells in HEPES-buffered Ringer's solution. Recovery from an acid load was sodium-dependent, completely inhibited by 100 microM amiloride, and unaffected by changes in potassium concentration between 6 and 25 mM. The results provide evidence in support of the presence of an amiloride-sensitive Na/H exchanger in antral cells from rabbit, guinea pig, and Necturus.