title: Na,K-ATPase inhibition alters tight junction structure and permeability in human retinal pigment epithelial cells.
abstract: Na,K-ATPase regulates a variety of transport functions in epithelial cells. In cultures of human retinal pigment epithelial (RPE) cells, inhibition of Na,K-ATPase by ouabain and K(+) depletion decreased transepithelial electrical resistance (TER) and increased permeability of tight junctions to mannitol and inulin. Electrophysiological studies demonstrated that the decrease in TER was due to an increase in paracellular shunt conductance. At the light microscopy level, this increased permeability was not accompanied by changes in the localization of the tight junction proteins ZO-1, occludin, and claudin-3. At the ultrastructural level, increased tight junction permeability correlated with a decrease in tight junction membrane contact points. Decreased tight junction membrane contact points and increased tight junction permeability were reversible in K(+)-repletion experiments. Confocal microscopy revealed that in control cells, Na,K-ATPase was localized at both apical and basolateral plasma membranes. K(+) depletion resulted in a large reduction of apical Na,K-ATPase, and after K(+) repletion the apical Na,K-ATPase recovered to control levels. These results suggest a functional link exists between Na,K-ATPase and tight junction function in human RPE cells.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California, Los Angeles 90095, USA. arajasekaran@mednet.ucla.edu
authors.forename: Sigrid A
authors.initials: SA
authors.lastname: Rajasekaran
authors.forename: Jane
authors.initials: J
authors.lastname: Hu
authors.forename: Jegan
authors.initials: J
authors.lastname: Gopal
authors.forename: Ron
authors.initials: R
authors.lastname: Gallemore
authors.forename: Sergey
authors.initials: S
authors.lastname: Ryazantsev
authors.forename: Dean
authors.initials: D
authors.lastname: Bok
authors.forename: Ayyappan K
authors.initials: AK
authors.lastname: Rajasekaran
mesh_terms: D000199:Actins / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D062465:Claudin-3; D017097:Electric Impedance; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007444:Inulin / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D062793:Occludin; D010042:Ouabain / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; C568122:CLDN3 protein, human; D015820:Cadherins; D062465:Claudin-3; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D008353:Mannitol; D010042:Ouabain; D007444:Inulin; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium