Enterochromaffin cell

Enterochromaffin cells, also known as EC cells, are a type of enteroendocrine cell found in the epithelium of the digestive tract. These cells are primarily located within the lining of the stomach and intestine, where they play a crucial role in the regulation of gastrointestinal function. Enterochromaffin cells are best known for their ability to produce and secrete serotonin (5-hydroxytryptamine, 5-HT), a key neurotransmitter involved in the regulation of gastrointestinal motility and secretion.

Function

Enterochromaffin cells are part of the body's enteric nervous system, often referred to as the "second brain" due to its autonomy and the vast network of neurons. The primary function of EC cells is the synthesis and release of serotonin in response to mechanical or chemical stimuli within the gut. Serotonin released by EC cells acts on the surrounding nervous tissue and smooth muscle cells, facilitating peristalsis and regulating gut motility. Additionally, serotonin plays a role in the modulation of intestinal secretion and the sensation of nausea and vomiting.

Location and Structure

Enterochromaffin cells are dispersed throughout the gastrointestinal tract but are most abundant in the duodenum and the ileum. Morphologically, these cells are characterized by their flask-shaped structure, with a broad base in contact with the basal lamina and a narrow apex that reaches the gut lumen. This positioning allows EC cells to directly sense the luminal environment and respond appropriately.

Pathophysiology

Alterations in the number or function of enterochromaffin cells can lead to various gastrointestinal disorders. For instance, an increase in EC cell number is associated with Irritable Bowel Syndrome (IBS), particularly the subtype characterized by diarrhea (IBS-D). This is thought to be due to the overproduction of serotonin, leading to increased gut motility and secretion. Conversely, a decrease in serotonin levels has been linked to constipation-predominant IBS.

Furthermore, enterochromaffin cells can give rise to certain types of neuroendocrine tumors, known as carcinoid tumors. These tumors can produce excessive amounts of serotonin, leading to a collection of symptoms known as carcinoid syndrome, characterized by flushing, diarrhea, and, over time, heart valve damage due to the fibrotic effects of serotonin.

Research and Clinical Significance

Research into enterochromaffin cells and their function has expanded our understanding of gastrointestinal physiology and the pathogenesis of related disorders. Targeting the serotonin system, including the receptors and transporters involved in serotonin signaling, has been explored as a therapeutic approach for conditions like IBS and carcinoid syndrome. Drugs that modulate serotonin levels, such as serotonin receptor agonists and serotonin reuptake inhibitors, are currently used in the treatment of various gastrointestinal disorders.

See Also

• Gastrointestinal tract
• Serotonin
• Neuroendocrine tumor
• Irritable Bowel Syndrome