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- Title
Ammonia and gastric acid secretion: a key to understanding activity and regulation of the H[sup +],K[sup +]-ATPase.
- Authors
Hagen, Susan J.
- Abstract
Ammonia is a cytotoxic substance liberated during Helicobacter pylori infection that may be responsible, in part, for the significant reduction in gastric acid secretion in human patients. However, it is not clear how ammonia blocks acid secretion. Here, we investigate several potential pathways for ammonia blockade in gastric oxyntic cells. Methods: Stomachs from the bullfrog, Rana catesbeiana, were stripped and mounted in Ussing chambers. Four possible pathways of blockade were investigated: (1) blockade of basolateral K[sup +]-channel activity, (2) blockade of ion transport activity, (3) neutralization of secreted H[sup +] or (4) ATP depletion. Results: Addition of nutrient 10 mM NH[sub 4]Cl at pH 7.4, yielding 92.5 μM NH[sub 3] and 9.91 mM NH[sub 4][sup +], abolished acid secretion within 30 min. Inhibition of acid secretion did not occur by blockade of basolateral K[sup +]-channel activity or ion transport activity, nor did NH[sub 4][sup +] enter cells by substituting for Na[sup +] or K[sup +] on individual ion transporters. Furthermore, neutralization of the luminal solution by NH[sub 3] and/or ATP depletion cannot account for the total reduction in acid secretion. We demonstrate that NH[sub 4]Cl acts specifically on stimulated tissues. Conclusions: We show that small concentrations of ammonia completely block gastric acid secretion. We propose that inhibition of acid secretion occurs by blockade of an apical K[sup +]-channel, specifically inwardly rectifying K[sup +]-channels. Our data suggest that apical K[sup +]-channel activity may be essential for the regulation of acid secretion and could be a new therapeutic target for acid inhibitory drugs.
- Subjects
AMMONIA; GASTRIC acid; ADENOSINE triphosphatase; HELICOBACTER pylori
- Publication
Inflammopharmacology, 2002, Vol 10, Issue 4-6, p471
- ISSN
0925-4692
- Publication type
Article
- DOI
10.1163/156856002321544936