title: The role of paracellular pathways in isotonic fluid transport.
abstract: Paracellular pathways across "leaky" epithelia are the major route for transepithelial ionic diffusion. The permselective properties of these pathways suggest that they offer a watery environment through which ions diffuse in their hydrated forms. There is also suggestive evidence that, at least in some tissues, paracellular pathways provide a significant route for transepithelial water flow in response to an osmotic pressure difference; however, this has not as yet been definitively established. The effect of junctional complexes that are permeable to ions and water on the predictions of the standing-osmotic gradient model for isotonic water absorption is considered.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D002831:Choroid Plexus / Q000378:metabolism; D004058:Diffusion; D004848:Epithelium / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005704:Gallbladder / Q000378:metabolism; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007477:Ions; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008564:Membrane Potentials; D008954:Models, Biological; D009997:Osmotic Pressure; D012867:Skin / Q000378:metabolism; D001743:Urinary Bladder / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D007477:Ions; D014867:Water