Contribution of carbon monoxide-producing cells in the gastric mucosa of rat and monkey.

Recent studies have shown that carbon monoxide (CO) may function as a gaseous signaling molecule in a similar way to nitric oxide. In the gastrointestinal tract, immunoreactivity against a CO-producing enzyme, heme oxygenase-2 (HO-2), was reported in epithelial cells and neurons of submucosal and myenteric plexus. However, details of the epithelial cells in the gastric mucosa remain unknown. The aim of this study was to clarify if mRNA for HO-2 is expressed in the rat stomach, if HO-2 protein is present in the mucosa, and to define the cell types of the HO-2-immunoreactive cells. HO-2 mRNA and protein were detected in fundic and pyloric mucosa of rat stomach using an RNA protection assay and western blot analysis. Immunohistochemical study showed that HO-2 was localized in parietal cells of the fundic glands and gastrin cells of the pyloric glands of both rat and monkey. The results suggest that HO-2 enzyme is produced in the gastric mucosa, and that CO is released from parietal cells and gastrin cells.