An ultrastructural and cytochemical study of enteroendocrine cells of the pyloric antrum in the gerbil, Meriones unguiculatus.

Enteroendocrine cells of the gastric antrum have been examined in the gerbil, Meriones unguiculatus. Gastrin-secreting G cells were identified by immunocytochemical methods and by transmission electron microscopy. They were present in the lower and middle third of the pyloric antral glands. G cells were polyhedral in shape and often extended to the gland lumen where they presented a microvillous and pinocytotic surface. These cells were characterized by numerous electron-dense and immunoreactive secretory granules. Enterochromaffin cells were identified by a serotonin-specific formaldehyde-induced fluorescence method, and by electron microscopy which revealed pleomorphic secretory granules of varying electron densities. These cells also had luminal projections and had a shape and distribution essentially similar to those of the G cells. A third endocrine cell type was identified as Dl cell in the pyloric glands. This cell type was recognized by the presence of numerous secretory granules having an electron-dense core and a clear peripheral space, as also by the presence of microfilament bundles, especially in the perinuclear region. The functional correlates of these morphological observations are discussed with reference to their secretory product and the manner of its release, especially by the G cells.