pH regulatory mechanisms in rat pancreatic ductal cells.

The mechanisms underlying regulation of intracellular pH (pHi) by rat pancreatic duct cells were studied by use of the pH-sensitive, fluorescent, cytoplasmically trapped dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Cells exhibited a mean pHi of 7.18 +/- 0.14 in bicarbonate-buffered medium, as calculated from the BCECF fluorescence ratio. Removal of extracellular Na (Nao) caused an intracellular acidification that was rapidly reversed by Na replacement and occurred independently of Clo. Amiloride (10(-3) M) reversibly blocked Na-dependent recovery after Na-free-induced acidification. These results demonstrate the presence of a Na+-H+ exchange mechanism in pancreatic duct cells. Replacement of Clo with gluconate caused an intracellular alkalinization that was reversed by replacement of Cl. Application of the disulfonic stilbene derivatives, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and dihydro-DIDS (2 X 10(-4) M), resulted in block of both Cl-dependent recovery from Na-gluconate and the onset of alkalinization of transition from NaCl to Na-gluconate. Chloride-dependent alteration of pHi occurred independently of Nao. These results demonstrate the presence of an anion exchange mechanism consistent with Cl--HCO3- exchange. Thus pancreatic duct cells contain both Na+-H+ and Cl--HCO3- exchangers.