Histamine-2 receptor expression in gastric mucosa before and after Helicobacter pylori cure

Background: Helicobacter pylori infection prevents the occurrence of the tolerance phenomenon of Histamine-2 (H2) receptor antagonists. Gastro-esophageal reflux disease develops in some cases with the restoration of acid secretion after H. pylori eradication therapy. Aim: To clarify the mechanisms of H2 receptor restoration after the eradication of H. pylori on parietal cells. Methods: We enrolled 80 consecutive asymptomatic male patients with H. pylori infection, having chronic gastritis with or without the presence of peptic ulcers. Biopsy specimens from the greater curvatures at the mid-corpus of the stomach were obtained endoscopically from all subjects before and 12 weeks after the eradication of H. pylori. Degrees of gastric atrophy were evaluated by serum pepsinogen levels. The amounts of mRNA expression of H2 receptor were evaluated in each subject's gastric mucosa by real time reverse transcriptase-polymerase chain reaction (RT-PCR). Results: H2 receptor mRNA expression levels significantly correlated with serum pepsinogens I and 11 ratios. The expression level of H2 receptor mRNA was lower in subjects with hypergastrinemia. The median expression level of H2 receptor after H. pylori eradication was threefold greater than prior to treatment. In addition, its restoration became more pronounced in subjects with severe gastric atrophy. However, a comparatively low restoration of H2 receptor mRNA was found in subjects with hypergastrinemia. Conclusions: H2 receptor mRNA levels decrease with the progression of gastric atrophy induced by H. pylori infection, and arc restored after H. pylori eradication. Such expression levels of H2 receptor may explain a part of the tolerance phenomenon to H2 receptor antagonists.