The gastric acid secretagogue gastrin-releasing peptide and the inhibitor oxyntomodulin do not exert their effect directly on the parietal cell in the rat

Previous studies suggested that gastrin-releasing peptide (a neuropeptide found in rat oxyntic mucosa) and oxyntomodulin (a glucagon-containing peptide of mammalian gut) could directly affect the acid secretion of the parietal cells. We therefore studied their effect on gastric acid production in vitro by measuring [^l4C]-aminopyrine accumulation, a reliable index of H⁺ generation, in isolated rat parietal cells. However, neither gastrin-eleasing peptide nor oxyntomodulin influenced basal acid secretion or histamine-stimulated gastric acid secretion. Electron-microscopic studies of unstimulated and histamine-stimulated parietal cells confirmed that the cells retained the normal morphology of intracellular organelles and that the cells responded to physiological stimulation by marked expansion of the intracellular canaliculi.