Regulation of gastric acid secretion via modulation of a chloride conductance.
When gastric microsomes were purified from resting and stimulated rabbit mucosae, they were found to be generally similar in (H+ + K+)-ATPase activity, peptide composition in single-dimension sodium dodecyl sulfate-gel electrophoresis, and in size. In the stimulated vesicles, optimal proton transport activity was found at pH 7.4, 20-50 mM KCl, and 1 mM ATP-Mg. However, in the case of resting vesicles, the presence of valinomycin and an inward Cl-gradient was also necessary for Mg-ATP-dependent proton transport. Measurement of K+ and Cl-diffusion potentials using 3,3-dipropylthiadicarboxocyanine iodide as a potential sensitive dye showed that both resting and stimulated vesicles developed K+ gradient-dependent potentials in the presence of an impermeant anion, but that Cl- gradient-dependent potentials were observed only in the stimulated preparation. 86Rb+ self-exchange was found in both types of vesicles, but Cl- self-exchange was confined to vesicles derived from stimulated mucosae. Putative inhibitors of anion conductance such as furosemide and anthracene 9-carboxylic acid blocked proton transport, Cl- conductance, 36Cl- uptake, and Cl- exchange. The inhibition of proton transport was overcome by valinomycin. ATPase activity in the presence of nigericin, an H+:K+ exchanger, was unaffected by these inhibitors. K+ conductance, Rb+ uptake, and Rb+ exchange were insensitive to these inhibitors. Thus, activation of acid secretion by the stimulated parietal cell appears to involve at least the appearance of a discrete Cl- conductance in the pump-associated membrane.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002712:Chlorides / Q000494:pharmacology*; D005665:Furosemide / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D017506:H(+)-K(+)-Exchanging ATPase; D007700:Kinetics; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology; D011817:Rabbits; D013050:Spectrometry, Fluorescence
D002712:Chlorides; D005665:Furosemide; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase