Entrochromaffin

Enterochromaffin cells, commonly referred to as EC cells, are a class of enteroendocrine cells embedded in the mucosa of the gastrointestinal tract. They are named for their chromaffin staining properties when treated with chromium salts, a historic basis for their classification in the APUD cell family. These cells synthesize and store serotonin (5-hydroxytryptamine, 5-HT) and, to a lesser extent, other biogenic amines, releasing them in response to luminal stimuli.

EC cells are distributed throughout the GI tract with particularly high density in the small intestine and colon. They produce serotonin via tryptophan hydroxylase 1 (TPH1) and aromatic L-amino acid decarboxylase, packaging 5-HT in dense-core secretory granules for regulated exocytosis into the lamina propria. Most peripheral serotonin is derived from these cells.

Serotonin released by EC cells acts on the enteric nervous system to regulate gut motility, intestinal secretion, and vascular tone, and can influence sensations via vagal afferents. Serotonin release is triggered by nutrients, mechanical stimulation, and other luminal cues.

EC-cell tumors (carcinoids) arise mainly in the appendix or ileum and can cause carcinoid syndrome with flushing, diarrhea, wheezing, and elevated urinary 5-HIAA. Markers include chromogranin A and synaptophysin; treatment may involve surgery and somatostatin analogs. A distinction is made from gastric enterochromaffin-like (ECL) cells, which secrete histamine in response to gastrin.