Biol. Pharm. Bull. 28(2) 370—373 (2005)

by blocking H /K -ATPase at the terminal steps of gastric acid secretion process. So, PPIs are assumed that their potency of gastric antisecretory effect is stronger than that of the histamine H2-receptor antagonists. Omeprazole, one of the PPIs, was discovered by Fellenius et al. and is widely used in treatment of peptic ulcer, gastro esophageal reflux disease and eradication of Helicobacter pylori together with amoxicillin and clarithromycin. Furthermore, it is known that PPIs not only inhibit gastric acid secretion, but also protect gastric mucosa. But the mechanism except for gastric antisecretory effect is not known well. In recent years, there are some reports that the drugs to treat gastrointestinal diseases have been elucidated pharmacologically from the viewpoints of gastrointestinal peptide (somatostatin, motilin, gastrin, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP) and substance P (SP)) levels. Somatostatin inhibits secretion of motilin, gastrin and secretin, and participates in regulating gastrointestinal motility. Motilin has powerful fundic pouch motor-stimulating activity, and is one of the most important factors controlling the regular occurrence of phase-3 contractions of the migrating motor complex (MMC). VIP has vasodilating effect, and is an important neurotransmitter for the enteric nervous system. CGRP is known to inhibit acid secretion and to stimulate mucosal blood flow. SP coexists with CGRP in the sensory afferent neurons of the gastrointestinal mucosa. The purpose of this study is to examine the effects of omeprazole on plasma levels of gastrointestinal peptides (somatostatin-, gastrin-, motilin-, VIP-, CGRPand SP-immunoreactive substance (IS)).