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Localization of omeprazole and metabolites in the mouse
Abstract:
Omeprazole is a substituted benzimidazole which blocks gastric acid secretion by inhibiting H+K+ATPase. Radioactive omeprazole was given intravenously or orally to mice, and the distribution of the drug was investigated at various intervals by scintillation counting and by autoradiography. The half-life for radioactivity in the stomach was 14 hours versus 30-36 hours in the liver, kidneys and blood. At 16 hours after the drug was given, the radioactivity in the stomach was ten times higher than that in the liver and kidneys, and 100 times that in the blood. Whole-body autoradiography showed sustained high levels of radioactivity only in the gastric mucosa. Light microscopic autoradiographic investigations of the gastric mucosa from mice killed 1 or 16 hours after the drug was given revealed radioactivity in the parietal cells. By electron microscopy of gastric mucosa from the mouse killed 16 hours after omeprazole injection the isotope label was found mainly over the secretory surface and the tubulo-vesicles. At these locations H+K+ATPase has previously been demonstrated, and it is suggested that omeprazole--or its metabolites--binds to this enzyme.
Insights
Radioactive omeprazole concentrated in mouse stomachs, reaching 100 times blood levels. This study shows omeprazole targets gastric parietal cells, binding to the H+K+ATPase enzyme.
Area of Science:
- Pharmacology
- Gastroenterology
- Biochemistry
Background:
- Omeprazole is a benzimidazole derivative that inhibits gastric acid secretion.
- Its mechanism involves blocking the H+K+ATPase enzyme.
- Understanding omeprazole's distribution is crucial for its therapeutic application.
Purpose of the Study:
- To investigate the distribution and localization of radioactive omeprazole in mice.
- To determine the drug's affinity for gastric parietal cells and the H+K+ATPase enzyme.
Main Methods:
- Administration of radioactive omeprazole via intravenous and oral routes to mice.
- Scintillation counting and whole-body autoradiography to track drug distribution.
- Light and electron microscopy for cellular and subcellular localization.
Main Results:
- Omeprazole exhibited a longer half-life in the stomach (14 hours) compared to liver, kidneys, and blood (30-36 hours).
- Radioactivity was significantly higher in the gastric mucosa, 10-100 times greater than in other organs.
- Autoradiography confirmed high concentrations in gastric parietal cells, specifically at the secretory surface and tubulo-vesicles.
Conclusions:
- Omeprazole preferentially accumulates in the gastric mucosa.
- The drug localizes to parietal cells, the site of H+K+ATPase.
- Findings suggest omeprazole or its metabolites bind to the H+K+ATPase enzyme, confirming its mechanism of action.