We have used the fluorescence intensity ratio (excitation 490/439; emission 520-550 nm) of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to measure intracellular pH (pHi) in single oxyntic cells (OCs) within intact gastric glands isolated from rabbits. The fluorescence ratio was converted to pHi by exposing cells to high [K] Ringer plus 10(-5) M nigericin. Ratios varied linearly with pHi over the physiological range. When the bathing solution was changed from NaCl to Na gluconate Ringer, pHi increased from 7.0 to 7.4. The increase of pHi occurred equally rapidly in nominally CO2-HCO3-free solutions and in solutions containing 5% CO2 and 25 mM HCO3. This effect was reversible and blocked by 2 X 10(-4) M 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS). The DIDS block was bypassed by 10(-5) M tri-n-butyltin, a pharmacological Cl-OH exchanger. When the bathing solution was changed from NaCl to N-methyl-D-glucamine (NMG) Cl Ringer, pHi decreased reversibly from 7.0 to 6.8. It was also found that changing from NMG gluconate to Na gluconate Ringer caused pHi to increase from 7.1 to 7.3, and this alkalinization was blocked by 10(-3) M amiloride; changing from NMG gluconate to NMG Cl Ringer caused pHi to decrease to 6.7. We conclude that OCs contain separate Na-H and Cl-HCO3 exchangers. Similarities and differences between these exchangers and those present in other cell types are discussed.

The electrical properties of oxyntic cells were measured in intact isolated Necturus fundic mucosa by dissecting away the serosal muscle and connective tissue and impaling the oxyntic cells across their basolateral membranes. Their properties under resting [i.e., not secreting acid (10(-4) M serosal cimetidine)] and stimulated (10(-4) M histamine) conditions were compared with those of surface cells impaled across their apical membranes in a separate set of experiments. Histamine hyperpolarized the transepithelial potential by 6-10 mV and reduced the transepithelial resistance by approximately 40%. The basolateral membrane potential (Vcs) of both cell types was significantly hyperpolarized by histamine, that of oxyntic cells from a resting value of -50 to -59 mV (P less than 0.001) and that of surface cells from -50 to -54 mV (P less than 0.05). Histamine also hyperpolarized the apical membrane potential (Vmc) of the oxyntic cells; however, the Vmc of surface cells was significantly depolarized. The ratio of the apical to basolateral cell membrane resistances Ra/Rb (delta Vmc/delta Vcs resulting from transepithelial current pulses) of resting oxyntic cells was 1.1 and that of surface cells was 3.6. Stimulation did not affect the Ra/Rb of either cell type. A tenfold increase in serosal K+ concentration depolarized Vcs and increased Ra/Rb of resting and stimulated oxyntic cells, indicating a significant basolateral K+ conductance. The results are consistent with a purely passive role for surface cells and indicate that stimulation results in a simultaneous decrease of both the apical and basolateral membrane resistances of the oxyntic cells.

Necturus urinary bladders stripped of serosal muscle and connective tissue were impaled through their basolateral membranes with microelectrodes in experiments that permitted rapid changes in the ion composition of the serosal solution . The transepithelial electrical properties exhibited a marked seasonal variation that could be attributed to variations in the conductance of the shunt pathway, apical membrane selectivity, and basolateral Na' transport .

Oxyntic cells that retain distinct morphological polarity between apical and basolateral membranes were isolated from the gastric mucosa of the amphibian Necturus. Patch-clamp techniques were applied to these cells to identify apical membrane ion channels associated with hydrochloric acid secretion. A single class of voltage-dependent, inwardly rectifying chloride channels was observed in the apical membranes of both resting and stimulated (acid-secreting) oxyntic cells. Stimulation of the cells with dibutyryladenosine 3',5'-monophosphate and isobutylmethylxanthine increased channel open probability and simultaneously increased apical membrane surface area. This chloride channel is probably responsible for electrogenic chloride secretion by the gastric mucosa and may also participate in the fluid- and enzyme-secretory functions of the oxyntic cell, analogous to the chloride channels found in the apical membranes of other exocrine cells.

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