REGULATION OF CHLORIDE SECRETION IN MAMMALIAN COLON

A number of procedures or interventions which activate electrogenic ion transport in mammalian intestine are reviewed. Using in vitro models it is possible to demonstrate direct or indirect pathways to stimulate chloride secretion. Such activation, in vivo, would change the gut from a state of net water absorption to one of fluid secretion. The movement of water is driven by electrical and osmotic gradients set up as a consequence of opening regulated ion channels in epithelial cells. Secretagogues may govern epithelial intracellular second messenger pathways to regulate ion channel activity directly or by activation of membrane bound receptors on the surface of epithelial cells. In health or disease secretagogues may be derived from cells within the attendant lamina propria of the intestinal mucosa. Pharmacological techniques may be employed to determine which mediators contribute to indirect stimulation of electrogenic ion transport by activation of neurons or of immunocytes (mast cells or phagocytes). Dissection and reconstruction of models of intestinal hypersensitivity reactions show that neuro-immune networks which regulate intestinal ion transport appear to be complex, functionally integrated systems. Analysis of such interactions may identify cellular or humoral targets with which to examine novel diagnostic, preventative or therapeutic strategies with regard to intestinal diseases.