N alpha -methyl histamine is an unusual histamine metabolite which is produ
ced in the stomach infected by Helicobacter pylori and which was shown in a
nimals to stimulate gastric acid secretion and to release gastrin in vitro
isolated G-cells, but no information is available regarding its influence o
n gastric secretion and gastrin release in duodenal ulcer patients before a
nd after H. pylori eradication. In this study, we compared the effects of i
ntragastric administration of single or graded doses of N alpha -methyl his
tamine on gastric acid secretion and plasma gastrin levels in 16 male duode
nal ulcer patients (aging from 35 to 48 years and weighing 65-82 kg) before
and after the eradication of H. pylori. Furthermore, the gastric luminal h
istamine and gastrin contents were determined before and after H. pylori er
adication. In H. pylori-infected duodenal ulcer patients, the intragastric
application of N alpha -methyl histamine failed to affect gastric acid secr
etion or plasma gastrin levels. Following eradication of H. pylori, gastric
luminal histamine and gastrin, and both basal gastric acid secretion and p
lasma gastrin levels, were significantly reduced. N alpha -methyl histamine
given intragastrically in graded doses to such H. pylori-eradicated duoden
al ulcer patients was found to increase dose-dependently gastric acid outpu
t reaching at a dose of 5 mg, about 80% of histamine maximum induced by i.v
. infusion of 25 mug/kg h of histamine dihydrochloride. We conclude that N
alpha -methyl histamine is a potent luminally active stimulant of gastrin r
elease and gastric acid secretion in H. pylori-eradicated patients when lum
inal histamine is low but is not effective in H. pylori infected patients w
hen luminal histamine is enhanced, possibly due to desensitization of gastr
in (G-cells) and acid-producing (parietal) cells by No alpha -methyl histam
ine produced excessively in H, pylori-infected stomach. (C) 2001 Published
by Elsevier Science B.V.