Gastric ammonia has a potent ulcerogenic action on the rat stomach.
BACKGROUND
The pathophysiological mechanism by which Helicobacter pylori induces mucosal injury has not been clarified. The aim of this study was to investigate the role of urea, urease, and ammonia in rat gastric mucosal lesions using an ex vivo chamber model.


METHODS
Two groups of rats, normotensive rats and those subjected to ischemia, were studied. The gastric mucosa was examined histologically and macroscopically, and the transmucosal potential difference was measured.


RESULTS
Instillation of urea into the stomach generated ammonia in the presence of urease. The amount of ammonia was increased depending on the concentration of urea and was closely associated with the severity of the histological lesions. The exposure of the stomach to 15-60 mmol/L ammonium hydroxide induced both a reduction in transmucosal potential difference and microscopic damage to the gastric mucosa in normotensive rats. Moreover, 15-60 mmol/L ammonium hydroxide produced severe macroscopic gastric lesions in the rats subjected to ischemia.


CONCLUSIONS
These results show that ammonia is deleterious to the gastric mucosa and suggest the importance of urea, urease, and ammonia in the pathophysiology of gastric diseases in H. pylori-infected patients.
Murakami
M
M
Department of Geriatric Medicine, Faculty of Medicine, Kyoto University, Japan.
Saita
H
H
Teramura
S
S
Dekigai
H
H
Asagoe
K
K
Kusaka
S
S
Kita
T
T
D000200:Action Potentials; D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology; D016480:Helicobacter pylori / Q000201:enzymology / Q000472:pathogenicity; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013276:Stomach Ulcer / Q000139:chemically induced*; D014508:Urea / Q000378:metabolism; D014510:Urease / Q000633:toxicity
D000641:Ammonia; D014508:Urea; D014510:Urease