A study of two enteroendocrine cells in the duodenum of the gerbil-Meriones unguiculatus.

Gastrin-secreting G cells and enterochromaffin cells have been examined in the duodenum of the gerbil-Meriones unguiculatus. G cells examined by immunoperoxidase and immunofluorescence methods were seen primarily located in the mucosa lining the villi and rarely in the glands of Lieberkühn. They were flask-shaped cells that extended from the basal lamina to the mucosal surface. Immunoreactive gastrin was localized all over in the cytoplasm but was especially concentrated in the juxtanuclear and subnuclear regions. Enterochromaffin cells were identified by a serotonin-specific formaldehyde-induced fluorescence method. These cells were also primarily located in the duodenal villi, were flask-shaped and revealed an intense yellow fluorescence that was especially concentrated in the subnuclear cytoplasm. At the ultrastructural level the enterochromaffin cells showed numerous pleomorphic electron-dense secretory granules especially located in the subnuclear cytoplasm. Microfilament bundles were often observed, especially in the perinuclear region.