Module 7: Figure colon function
Control of fluid absorption and secretion by the colon epithelial cell.
There is a dynamic balance between fluid absorption and secretion across the epithelial cells of the colon. Aldosterone enhances absorption by increasing the expression of the Na+/K+-ATPase and the epithelial Na+ entry channel (ENaC). Secretion is activated by various intracellular messengers that control the activity of the co-transporter that brings Cl− into the cell and the cystic fibrosis transmembrane conductance regulator (CFTR) channel that passes Cl− into the lumen (for details, see Module 7: Figure intestinal secretion).