Table 1.
Overview of the main endocrine cells in the gastrointestinal tract
| Cell content | Localization | Source of release | Actions |
| Serotonin (5-HT) | EC cells in the stomach, large and small intestines | Noradrenalin; acetylcholine; acidification and intraluminal pressure | Inhibits gastric emptying and stimulates colonic motility; accelerates small- and large-intestine transit activates the submucosal sensory branch of the enteric nervous system that conveys sensation from the gut to the central nervous system |
| Histamine | EC-like cells in the gastric oxyntic mucosa | Vagus nerve stimulation and inhibited by somatostatin | Stimulates gastric acid secretion |
| Somatostatin | The stomach, and large and small intestines | Mixed meal and acidification of the stomach | Inhibits intestinal contraction; inhibits gut exocrine and neuroendocrine secretion |
| Ghrelin | Gastric oxyntic mucosa | Protein and fat ingestion; suppressed by carbohydrate ingestion | Increases appetite and food intake; stimulates gastric and intestinal motility |
| Gastrin | Gastric antral mucosa | Intraluminal peptides; amino acids; calcium; amines; low pH and prostaglandins. Somatostatin inhibits release | Stimulates gastric acid secretion and histamine release; trophic action on gastric mucosa; stimulates contraction of the LES and antrum |
| CCK | Small intestine, especially the duodenum | Intraluminal protein and fat and inhibited by somatostatin | Inhibits gastric emptying; stimulates gallbladder contraction and intestinal motility; stimulates pancreatic exocrine secretion and growth; regulates food intake |
| Secretin | Small intestine, especially the duodenum | Acidification and inhibited by somatostatin | Stimulates pancreatic bicarbonate and fluid secretion; inhibits gastric emptying; inhibits contractile activity of the small and large intestines |
| GIP | Small intestine, especially the duodenum | Intraluminal glucose; amino acids and fat | Incretin action; inhibits gastric acid secretion |
| Motilin | Small intestine, especially the jejunum | Protein and fat ingestion | Induces phase-III migrating motor complex; stimulates gastric emptying; stimulates contraction of the LES |
| Neurotensin | Small intestine | Fat | Stimulates pancreatic section; inhibits gastric secretion; delays gastric emptying; stimulates colon motility |
| PYY | Terminal ileum and large intestine | Protein-rich meals | Delays gastric emptying; inhibits gastric and pancreatic secretion, stimulates the absorption of water and electrolytes; major mediator of the ileal brake |
| PP | Terminal ileum and large intestine | Protein-rich meals | Inhibits pancreatic secretion; stimulates gastric acid secretion; relaxes the gallbladder; stimulates motility of the stomach and small intestine |
| Enteroglucagon (oxyntomodulin) | Terminal ileum and large intestine | Intraluminal carbohydrates and fat | Inhibits gastric and pancreatic secretion; reduces gastric motility; has some incretin effect |
| Chromogranin | All gastrointestinal tract segments | Ingestion of a meal | Induces formation, sorting, and release of secretory granules of the gut endocrine/paracrine cells; an inflammatory mediator |
CCK: Cholecystokinin; EC: Enterochromaffin; GIP: Gastric inhibitory peptide; LES: Lower esophageal sphincter; PP: Pancreatic polypeptide; PYY: Peptide YY.