Vasopressin increases na-k-2cl cotransporter expression in thick ascending limb of henle_s loop. Kim, Gheun-Ho, Carolyn A. Ecelbarger, Carter Mitchell, Randall K. Packer, James B. Wade, and Mark A. Knepper. 1Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, 2Department of Biological Sciences, George Washington University, Washington, DC 20052, 3Department of Physiology, University of Maryland College of Medicine, Baltimore, MD 21201
APStracts 5:0176F, 1998.
in response to long term increases in circulating vasopressin concentration is associated with increased expression levels of the apical Na-K-2Cl cotransporter in the rat thick ascending limb, we have carried out immunoblotting and immunofluorescence studies using affinity-purified, peptide-directed antibodies. Semiquantitative immunoblotting studies demonstrated a marked increase in Na-K-2Cl contransporter band density in response to restriction of water intake to 15 ml/day for 7 days (193% of controls). In contrast, the expression level of two other apical proteins of the thick ascending limb (the type 3 Na-H exchanger and Tamm-Horsfall protein) were unchanged in the outer medulla. A 7-day subcutaneous infusion of the V2 receptor selective vasopressin analog, dDAVP, to Brattleboro rats also markedly increased Na-K-2Cl cotransporter expression in the outer medulla (183% of controls). Immunofluorescence localization in outer medullary tissue sections confirmed the increase in Na-K-2Cl cotransporter expression in response to dDAVP. We conclude that vasopressin strongly upregulates the expression of the Na-K-2Cl cotransporter of the thick ascending limb, a process which is likely to play an important role in the long-term regulation of the countercurrent multiplication system. 

Received 29 July 1998; accepted in final form 1 October 1998.
APS Manuscript Number F186-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 20 October 1998