Electrolyte transport across the basolateral membrane of the parietal cells.
The ion-transport properties of the basal lateral membranes of intact isolated parietal cells were studied at the cellular and subcellular level. The presence of an amiloride-sensitive Na+:H+ exchange was demonstrated in cells by proton gradient-driven Na+ uptake and by changes in cell pH as monitored by dimethylcarboxylfluorescein fluorescence both in a fluorimeter and on single isolated cells using a fluorescence microscope and an attached intensified photodiode array spectrophotometer. The presence of the Na+:H+ antiport in vesicles was shown both by intravesicular acidification monitored by acridine orange fluorescent quenching and by proton gradient-dependent Na+ uptake. The presence of Cl-:HCO-3 exchange was determined in intact cells by monitoring changes in cell pH due to Cl- uptake and was shown to be 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid- and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid-sensitive. In vesicles, Cl-:HCO-3 exchange was demonstrated by Cl- flux measurement. The apparent affinities for both Cl- and HCO-3 on either side of the membrane were determined to be Km Cli = 20 mM, Km Clout = 17.5 mM, Km HCO-3in = 2.5 mM, and Km HCO-3out = 7.5 mM. A K+ conductance in cells and vesicles was demonstrated by monitoring K+ gradient-dependent 86Rb uptake. No evidence was found for the presence of a Cl- conductance in either cells or vesicles but a H+ conductance was found to be present in vesicles but not in intact cells. In the latter, by determining the effect of either Na+ or Cl- gradients on cell pH and by flux calculations it was concluded that the Cl-:HCO-3 exchange was the major passive flux mechanism for pH regulation in this cell type.
D000584:Amiloride / Q000378:metabolism; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010295:Parietal Cells, Gastric / Q000648:ultrastructure*; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D001639:Bicarbonates; D002712:Chlorides; D004573:Electrolytes; D000584:Amiloride; D006859:Hydrogen; D012964:Sodium; D012413:Rubidium; D011188:Potassium