Enterochromaffin

Enterochromaffin cells, or EC cells, are enteroendocrine cells in the mucosa of the gastrointestinal tract that synthesize and secrete serotonin (5-hydroxytryptamine, 5-HT) and other mediators. They are the most abundant type of enteroendocrine cells in the gut and are distributed along the mucosa from stomach to rectum, with higher density in the small intestine and colon.

EC cells release 5-HT in response to luminal and mechanical stimuli. The serotonin released acts on nearby enteric neurons and smooth muscle to regulate intestinal motility, secretion, and sensation. It can also influence vascular tone and local immune interactions in the mucosa. Serotonin synthesis is catalyzed by tryptophan hydroxylase 1 (TPH1); the transmitter is stored in dense-core secretory granules and released by exocytosis, then reabsorbed by the serotonin transporter (SERT) and metabolized by monoamine oxidase.

Clinical significance of EC cells includes their role as a source of enteroendocrine tumors. EC cell–derived tumors, called carcinoids, can cause an overproduction of serotonin. When metastasized to the liver, serotonin may enter the systemic circulation, leading to carcinoid syndrome, which is characterized by flushing, diarrhea, wheezing, and eventually right-sided heart disease. Diagnosis typically involves elevated urinary 5-HIAA or plasma serotonin levels and imaging; treatment may include somatostatin analogs, surgical resection, and targeted therapies.

EC cells are part of the diffuse neuroendocrine system. They are distinct from gastric enterochromaffin-like (ECL) cells, which secrete histamine in the gastric mucosa under gastrin control.