N alpha-methylhistamine: association with Helicobacter pylori infection in humans and effects on gastric acid secretion.
Infection with the bacterium Helicobacter pylori is associated with altered gastric acid secretion and gastrointestinal disease. Recent work has suggested that N alpha-methylhistamine, produced by the bacterium and acting on histamine receptors in gastric tissue, might be involved. Gastric juice and tissue biopsies from infected patients have been analysed for the presence of N alpha-methylhistamine using a specific and sensitive assay based on gas chromatography mass spectrometry. N alpha-Methylhistamine was detected in five of seven samples of gastric juice from infected patients (5-180 pmol/ml) but was absent in nine uninfected subjects. The compound was not found in fundic and antral biopsies from both subject groups. Helicobacter pylori, cultured on agar and in broth with and without added histamine, was found not to produce detectable levels of N alpha-methylhistamine. Instillation of this compound at 10(-5) mol/l into the gastric lumen produced a significant increase in acid secretion in vivo while plasma gastrin concentration remained unchanged. N alpha-Methylhistamine in gastric juice appears therefore to be associated with infection, although this product is not generated directly by the bacterium. The concentrations found are below those required to affect acid secretion or gastrin production in vivo, although higher local concentrations may exist around a site of infection.
Murray
S
S
Section of Clinical Pharmacology, Division of Medicine, Imperial College School of Medicine, Hammersmith Hospital, Ducane Road, London W12 ONN, UK. s.murray@ic.ac.uk
Taylor
G W
GW
Karim
Q N
QN
Bliss
P
P
Calam
J
J
D008401:Gas Chromatography-Mass Spectrometry; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism; D005755:Gastrins / Q000097:blood; D016481:Helicobacter Infections / Q000378:metabolism*; D016480:Helicobacter pylori / Q000472:pathogenicity*; D006801:Humans; D008761:Methylhistamines / Q000378:metabolism*; D012680:Sensitivity and Specificity
D005755:Gastrins; D008761:Methylhistamines; C069357:alpha-methylhistamine