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Background: We investigated the effects of rabeprazole compared with those of omeprazole on enterochromaffin-like cells and parietal cells in rats., Methods: Rabeprazole or omeprazole was administered for 7 days by intraperitoneal injection (100 mg/kg or 20mg/kg once a day) and the serum gastrin concentration, the antral density of G cells and D cells, fundic histamine content, fundic H+, K+-ATPase mRNA level, and parietal cell morphology were determined., Results: Both rabeprazole and omeprazole inhibited gastric acid secretion and increased the intragastric pH to over 6.5, as well as causing a marked increase in the serum gastrin concentration. The serum gastrin level was lower with rabeprazole treatment than with omeprazole treatment at both doses. Also, the antral G-cell density was higher with omeprazole than with rabeprazole, while the increase in both the histamine content and the H+, K-ATPase mRNA level in the fundic mucosa was higher with omeprazole treatment at both doses, with the difference being significant at 100 mg/kg. Ultrastructural examination indicated that the stimulation of parietal cells by omeprazole was stronger than that by rabeprazole., Conclusions: Rabeprazole treatment does not drive enterochromaffin-like cells and parietal cells as strongly as omeprazole treatment despite its potent acid suppressive effect, suggesting that it represents a new generation of proton pump inhibitors.

Purpose: The purpose of this study was to investigate the mechanism of the regulation of histamine synthesis in enterochromaffin-like cells, chemically and structurally, by treatment with omeprazole and pirenzepine.Methods: The ultrastructures of enterochromaffin-like cells and parietal cells were examined in rats treated with oral omeprazole (20 mg/kg) or intraperitoneal pirenzepine (1 mg/kg) administration. Serum gastrin concentrations, mRNA levels of H+-K+-ATPase and histidine decarboxylase, and the fundic concentrations of somatostatin and histamine were determined.Results: Pirenzepine treatment suppressed omeprazole-induced increases in serum gastrin levels and mRNA levels of H+-K+-ATPase and histidine decarboxylase. Pirenzepine also decreased omeprazole-induced increases of histamine concentration in fundic mucosa. Pirenzepine elevated somatostatin mRNA level, previously decreased by omeprazole treatment, in fundic mucosa. In the cytoplasm of enterochromaffin-like cells, omeprazole markedly reduced the numbers of vesicles and granules, but significantly increased their diameters, whereas pirenzepine treatment changed neither of these features. The densities and diameters of both vesicles and granules produced by treatment with omeprazole and pirenzepine were between those produced by treatment with omeprazole alone and pirenzepine alone.Conclusions: Omeprazole-induced hypergastrinemia and pirenzepine-induced somatostatin synthesis play important roles not only in histamine synthesis but also in ultrastructural changes in enterochromaffin-like cells. [ABSTRACT FROM AUTHOR]

Background. The combination of omeprazole, amoxicillin, and clarithromycin is a common regimen against Helicobacter pylori. Several recent studies have shown that smoking, high intragastric acidity, and the degree of histological gastritis are associated with H. pylori eradication failure. Materials and Methods. One hundred and thirty-seven H. pylori–positive patients were treated with a 1-week regimen composed of omeprazole, 20 mg once daily; amoxicillin, 500 mg; and clarithromycin, 200 mg thrice daily. Success of the treatment was evaluated by histology and the 13C-urea breath test at least 4 weeks after completion of therapy. Data about age, gender, alcohol intake, smoking habits, and previous proton pump inhibitor intake were collected in patient interviews. We evaluated fasting gastric pH and the degree of histological gastritis before eradication of H. pylori. Results. The overall eradication of H. pylori at 4 weeks was successful in 98 of 137 patients (72%). On the multivariate analysis, a low grade of inflammation in the antrum (p ≤ .01; 95% confidence interval [CI], 2.34–16.75), low grade of activity in the fundus (p ≤ .05; 95% CI, 1.31–9.65), and smoking (p ≤ .05; 95% CI, 1.27–6.82) were the significant independent factors predicting treatment failure. Conclusions. These findings indicate that H. pylori eradication therapy with omeprazole, amoxicillin, and clarithromycin is less effective in patients who smoke and more effective in patients with high scores of antral inflammation and fundal activity at baseline biopsy. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate whether gastrin regulates morphological changes and alpha-subunit gene expression in parietal cells through the gastrin/CCK-B receptor on enterochromaffin-like cells by histamine release. Treatment with 100 mg/kg of YM022, a potent and selective gastrin/CCK-B receptor antagonist, for one week in rats did not alter mRNA levels of histidine decarboxylase or H+, K+-ATPase. However, parietal cell morphology predominantly changed to the resting form, although the serum gastrin concentration was significantly increased. Additional treatment with YM022 and oral omeprazole, 100 mg/kg, for one week markedly suppressed the increases of mRNA levels of histidine decarboxylase and H+, K+-ATPase and completely blocked the morphological transformation of the parietal cells to a stimulated form induced by treatment with omeprazole alone. This indicates that the morphological transformation of parietal cells to an activated form with a subsequent increase in H+, K+-ATPase synthesis caused by hypergastrinemia is mediated by increased histidine decarboxylase gene expression in enterochromaffin-like cells via gastrin/CCK-B receptors. [ABSTRACT FROM AUTHOR]

Objectives: We investigated the effects of short-term administration of omeprazole on the regulation of antral gastrin and somatostatin in 15 healthy men. Methods: Seven of these men were administrated 20 mg, and eight were given 40 mg of omeprazole for 8 days each. All subjects were examined before the first dose and after the last dose. Results: Each dose significantly increased the basal serum gastrin level. Although the dose of omeprazole 20 mg/day had no significant affect on the antral somatostatin content, omeprazole 40 rag/day increased the antral gastrin content and decreased the antral somatostatin content significantly. Both doses significantly increased in the antral gastrin mRNA level. However, neither dose significantly affected the antral somatostatin mRNA level. Conclusions: This study shows reciprocal changes between the antral content of gastrin and somatostatin following omeprazole administration. These results indicate that antral somatostatin may be involved in the hypersecretion of gastrin produced by omeprazole in humans. [ABSTRACT FROM AUTHOR]