title: Effects of Osmolality on Paracellular Transport in MDCK II Cells.
abstract: Epithelia separate apical and basal compartments, and movement of substances via the paracellular pathway is regulated by tight junctions. Claudins are major constituents of tight junctions and involved in the regulation of tight junction permeability. On the other hand, the osmolality in the extracellular environment fluctuates in association with life activity. However, effects of osmotic changes on the permeaibility of claudins are poorly understood. Therefore, we investigated the effects of osmotic changes on the paracellular transport in MDCK II cells. Interestingly, apical hyposmolality decreased cation selectivity in the paracellular pathway gradually with time, and the elimination of the osmotic gradient promptly restored the cation selectivity. Apical hyposmolality also induced bleb formation at cell-cell contacts and changed the shape of cell-cell contacts from a jagged pattern to a slightly linear pattern. In claudin-2 knockout MDCK II cells, the decrease of cation selectivity, the bleb formation, nor the changes in the shape of cell-cell contacts was observed under the apical hyposmolality. Our findings in this study indicate that osmotic gradient between apical and basal sides is involved in the acute regulation of the cation selective property of claudin-2 channels.
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Shinsaku
authors.identifier: http://orcid.org/0000-0002-3726-7775
authors.initials: S
authors.lastname: Tokuda
authors.affiliation: Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hirai
authors.affiliation: Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Japan.|Department of Physiological Sciences, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan.
authors.forename: Mikio
authors.initials: M
authors.lastname: Furuse
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D005614:Freeze Fracturing; D055786:Gene Knockout Techniques; D061985:Madin Darby Canine Kidney Cells; D009994:Osmolar Concentration; D021381:Protein Transport; D062725:Tight Junction Proteins / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism; D059008:Time-Lapse Imaging
chemical_list: D000199:Actins; D062725:Tight Junction Proteins