Cells possessing glucagon- and glucagon-like immunoreactivity (GLI) were studied by an indirect immunofluorescence technique in the normal canine gastrointestinal mucosa and pancreas.
Glucagon-immunoreactivity was demonstrated in the basal-granulated cells in the deeper portion of the fundic gland of the stomach as well as in the A cells of the pancreatic islet. GLI-positive basal-granulated cells were found in the fundus of the stomach, jejunum, ileum and colon. None of them were found in the pyloric antrum and duodenum. Careful examination of the immunofluorescence specimens gave us the impression that essentially every GLI-positive cell in the gastric fundus and pancreas contained glucagon.
It was observed that the GLI-positive cells in the jejunum, ileum and colon were open in type reaching the lumen with their tapered luminal process, whereas the glucagon/GLI-positive cells in the stomach were always separated from the lumen by a layer of other epithelial cells so that they were closed in type.
The possible difference in the way of stimulus-reception between the GLI-positive cells in the intestine and glucagon/GLI-positive cells in the stomach was discussed with particular reference to the idea that basal-granulated cells could receive information for their secretory activity not only from the gut lumen but also from the blood side.