Exocytosis in the antral gastrin cells of mouse, rat, and guinea pig after stimulation by carbamylcholine

Abstract

In order to capture the exocytotic figures of gastrin cells in the pyloric antrum of the stomach, we examined antral cells of the mouse, rat, and guinea pig by electron microscopy following stimulation with the cholinergic secretagogue carbamylcholine. Increased numbers of omega profiles indicative of exocytosis were seen in the basal or lateral cell membrane after stimulation with carbamylcholine. The number of exocytotic figures in stimulated gastrin cells was higher in the guinea pig than in the mouse and rat. Coated and non-coated omega profiles and coated pits in the plasma membrane were smaller than the secretory granules. Omega profiles with or without electron-dense contents were seen. Coated and non-coated vesicles were often visible near the plasma membrane of stimulated gastrin cells in all three species, large cytoplasmic vacuoles also being found in the guinea pig. In the mouse pretreated with horseradish peroxidase, reaction deposits were observed in the omega profiles and in microvesicles near the plasma membrane. These results suggest that, after exocytosis, membrane retrieval and endocytosis occur in the gastrin cells.

Classification of gastric endocrine cells at the light and electron microscopical levels

“…A release of the stored gastrin from the granules into the cytoplasm and from there into the bloodstream was suggested (Forssmann and Orci, 1969;Track et al, 1978). Recent investigations, however, have shown that under appropriate stimulation gastrin is released from the granules through a mechanism of exocytosis in keeping with all other peptide-secreting endocrine cells (Oomori et al, 1997).…”