Secretion cells in the gastrointestinal tract.

The morphology and distribution of secretin (S) cells were investigated in the human and the dog. S cells were well-visualized by the indired immunofluorescence antibody technique, using a highly specific rabbit anti-secretin sera. The fluorescence reaction was not blocked by an excess amount of gastrin, cholecystokinin, glucagon, vasoactive intestinal polypeptide, or motilin, whereas secretin blocked the reaction. S cells were seen in the mucosa of the antrum and duodenum in both humans and dogs, and throughout the entire length of the canine small intestine. They were not found in the mucosa of the esophagus, fundus of the stomach, or rectum. These cells were either pyramidal in shape or pearshaped and were one-third of the size of gastrin cells. The possible significance of S-cell distribution in the antrum and small intestine is discussed.