Anion exchange in oxyntic cell apical membrane: relationship to thiocyanate inhibition of acid secretion.
The effects of SCN- on H+-accumulation by inside-out gastric vesicles derived from the apical membrane of secreting oxyntic cells are reported. SCN- inhibited the formation of pH gradients in Cl- and isethionate media. In Cl-, the concentration of SCN- required to achieve a certain degree of inhibition of H+ uptake (or dissipation of performed gradients) was increased with the increase in Cl- concentration, indicating some competitive phenomena between these anions. Comparison of the rates of dissipation of similar pH gradients achieved in Cl- vs. isethionate suggested the existence of a fast Cl-/SCN- exchange. In addition, direct isotopic fluxes confirmed the existence of rapid anion exchange and K-salt transport for both Cl- and SCN-. The rates of anion-exchange and K-salt transport were of similar magnitude, and the rates for SCN- in either countertransport against Cl- or cotransport with K+ were twice as fast as the equivalent values for Cl-. These mediated pathways in the apical membrane provide the possible means for rapid access of SCN- to the acidic canalicular spaces of the oxyntic cell that is implicit in recent proposals to explain SCN- inhibition of gastric HCl secretion.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000838:Anions / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D002713:Chlorine; D005744:Gastric Acid / Q000378:metabolism*; D017506:H(+)-K(+)-Exchanging ATPase; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011522:Protons; D011817:Rabbits; D011868:Radioisotopes; D013861:Thiocyanates / Q000378:metabolism / Q000494:pharmacology*
D000838:Anions; D002712:Chlorides; D011522:Protons; D011868:Radioisotopes; D013861:Thiocyanates; D002713:Chlorine; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; C031760:thiocyanate; D011188:Potassium