Topographic distribution pattern of morphologically different G cells in the murine antral mucosa

Gastrin-secreting enteroendocrine cells (G cells) in the antrum play an important role in the regulation of gastric secretion, gastric motility and mucosal cell proliferation. Recently we have uncovered the existence of two subpopulations of G cells with pivotally different morphology and a distinct localization in the antral invaginations; the functional implications of the different G cell types are still elusive. In this study a transgenic mouse line in which EGFP is expressed under the control of a gastrin promoter was used to elucidate the distribution pattern of the two G cell types throughout the different regions of the antrum. The results of immunohistochemical analyses revealed that G cells were not equally distributed along the anterior/posterior axis of the antrum. The "typical" pyramidal- or roundish-shaped G cells, which are located in the basal region of the antral invaginations, were more abundant in the proximal antrum bordering the corpus region but less frequent in the distal antrum bordering the pylorus. In contrast, the "atypical" G cells, which are located in the upper part of the antral invaginations and have a spindle-like contour with long processes, were evenly distributed along the anterior/posterior axis. This characteristic topographic segregation supports the notion that the two G cell types may serve different functions. A comparison of the antrum specific G cells with the two pan-gastrointestinal enteroendocrine cell types, somatostatin-secreting D cells and serotonin-secreting enterochromaffin (EC) cells, revealed a rather similar distribution pattern of G and D cells, but a fundamentally different distribution of EC cells. These observations suggest that distinct mechanisms govern the spatial segregation of enteroendocrine cells in the antrum mucosa.