APStracts 10:0066C, 2003.

Na,K-ATPase inhibition alters tight junction structure and permeability in human retinal pigment epithelial cells. Rajasekaran, Sigrid A., Jane Hu, Jegan Gopal, Ron Gallemore, Sergey Ryazantsev, Dean Bok, and Ayyappan K. Rajasekaran. 1Department of Pathology and Laboratory Medicine, 2Jules Stein Eye Institute, 4Department of Biological Chemistry, 5Department of Neurobiology and Brain Research Institute, University of California, Los Angeles 90095; and 3Retina-Vitreous Associates Medical Group, Los Angeles, California 90278

APStracts 10:0066C, 2003.

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.

Received 1 August 2002; accepted in final form 2 February 2003
APS Manuscript Number C355-2.
Article publication pending Am J Physiol Cell Physiol
ISSN 1080-4757 Copyright 2003 The American Physiological Society.
Published in APStracts on 25 March 2003