Human gastrin: A Helicobacter pylori-specific growth factor

Background and Aims: Helicobacter pylori resides within the gastric mucosa, a niche hostile to other microorganisms. Human gastrin levels are elevated after infection and return to normal after eradication. The aim of this study was to test the direct effect of gastrin on the growth of H. pylori. Methods: H. pylori and control bacteria were grown with gastrin or control peptides and growth rate was determined. ¹²⁵I-labeled gastrin was used to determine uptake. Results: Human gastrin stimulated H. pylori growth in a specific, dose-dependent manner. Gastrin shortened the lag time, increased growth rate in the logarithmic phase, and increased final bacterial concentration at the stationary phase. These effects were shown over a wide concentration range, including physiological luminal and serum levels. Labeled gastrin uptake was inhibited by unlabeled gastrin. Controls consisting of cholecystokinin and pentagastrin inhibited gastrin uptake but did not stimulate growth. In contrast, somatostatin and epidermal growth factor had no effect on either gastrin uptake or bacterial growth. These results suggest a structurally restricted, receptor-mediated, gastrin- specific effect. Conclusions: Human gastrin is a specific growth factor for H. pylori and may have a role in the adaptation of H. pylori to its unique habitat.