title: Water does not flow across the tight junctions of MDCK cell epithelium.
abstract: Although it has been known for decades that the tight junctions of fluid-transporting epithelia are leaky to ions, it has not been possible to determine directly whether significant transjunctional water movement also occurs. An optical microscopic technique was developed for the direct visualization of the flow velocity profiles within the lateral intercellular spaces of a fluid-absorptive, cultured renal epithelium (MDCK) and used to determine the velocity of the fluid flow across the tight junction. The flow velocity within the lateral intercellular spaces fell to near zero adjacent to the tight junction, showing that significant transjunctional flow did not occur, even when transepithelial fluid movement was augmented by imposition of osmotic gradients.
authors.affiliation: Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1603, USA. kovbasno@fido.nhlbi.nih.gov
authors.forename: O
authors.initials: O
authors.lastname: Kovbasnjuk
authors.forename: J P
authors.initials: JP
authors.lastname: Leader
authors.forename: A M
authors.initials: AM
authors.lastname: Weinstein
authors.forename: K R
authors.initials: KR
authors.lastname: Spring
mesh_terms: D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure*; D009994:Osmolar Concentration; D019108:Tight Junctions / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water