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Am J Physiol Regul Integr Comp Physiol 295: R1713-R1719, 2008. First published September 10, 2008; doi:10.1152/ajpregu.90596.2008
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WATER AND ELECTROLYTE HOMEOSTASIS

Effect of claudins 6 and 9 on paracellular permeability in MDCK II cells

David Sas,1 Mingchang Hu,1,2 Orson W. Moe,2,3 and Michel Baum1,2

Department of 1Pediatrics, 2Internal Medicine, and 3Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas

Submitted 13 July 2008 ; accepted in final form 8 September 2008

The neonatal proximal tubule has a lower permeability to chloride, higher resistance, and higher relative sodium-to-chloride permeability (PNa/PCl) than the adult tubule, which may be due to maturational changes in the tight junction. Claudins are tight-junction proteins between epithelial cells that determine paracellular permeability characteristics of epithelia. We have previously described the presence of two claudin isoforms, claudins 6 and 9, in the neonatal proximal tubule and subsequent reduction of these claudins during postnatal maturation. The question is whether changes in claudin expression are related to changes in functional characteristics in the neonatal tubule. We transfected claudins 6 and 9 into Madin-Darby canine kidney II (MDCK II) cells and performed electrophysiological studies to determine the resultant changes in physiological characteristics of the cells. Expression of claudins 6 and 9 resulted in an increased transepithelial resistance, decreased chloride permeability, and decreased PNa/PCl and PHCO3/PCl. These findings constitute the first characterization of the permeability characteristics of claudins 6 and 9 in a cell model and may explain why the neonatal proximal tubule has lower permeability to chloride and higher resistance than the adult proximal tubule.

resistance; proximal tubule; neonate


Address for reprint requests and other correspondence: M. Baum, Dept. of Pediatrics, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235 (e-mail: michel.baum{at}utsouthwestern.edu)






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