Background: Ghrelin, a recently discovered peptide hormone, has been shown to be produced mainly by the A-like cells of the gastric mucosa. Ghrelin not only stimulates growth hormone (GH) release but also promotes gastric motility. While the effect of ghrelin on the gastric acid secretion in rats has been reported, no such reports appeared to date from studies in humans. Aim: To investigate the effect of ghrelin administration on the gastric pH in humans, using a novel wireless pH capsule (Bravo, Medtronic, Shoreview, MN, USA). Methods: Four healthy volunteers (male; average age, 35.0 years; Helicobacter pylori-negative) were enrolled. The pH capsule was attached endoscopically to the gastric mucosa and the data were transmitted to a portable receiver. Thirty minutes after a stabilization period, synthetic ghrelin (5 μg/kg body weight) was injected intravenously into the subjects and the data were monitored for more than 120 min while the subjects lay supine. Results: The average minimum gastric pH in four cases (1.2 ± 0.10) was significantly decreased after injection of ghrelin, as compared with the basal pH value (1.8 ± 0.06). The serum gastrin level, however, showed no change after the ghrelin injection. Conclusion: These results suggest that exogenous ghrelin could enhance gastric acid secretion in humans.
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