Pendrin Modulates ENaC Function by Changing Luminal HCO3− : Journal of the American Society of Nephrology (original) (raw)

Basic Research

Pech, Vladimir*; Pham, Truyen D.*; Hong, Seongun*; Weinstein, Alan M.†; Spencer, Kathryn B.*; Duke, Billy Jean‡; Walp, Eric§; Kim, Young Hee*; Sutliff, Roy L.*,§; Bao, Hui-Fang‡; Eaton, Douglas C.‡; Wall, Susan M.*,‡

Departments of *Medicine and

‡Physiology, Emory University School of Medicine, Atlanta, Georgia;

†Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York; and

§Atlanta Veterans Affairs Medical Center, Atlanta, Georgia

Correspondence: Dr. Susan M. Wall, Renal Division, WMB Room 338, 1639 Pierce Drive NE, Atlanta, GA 30322. Phone: 404-727-2525; Fax: 404-727-3425; E-mail: [email protected]

V.P. and T.D.P. contributed equally to this work.

Received December 16, 2009

Accepted July 28, 2010

Abstract

The epithelial Na+ channel, ENaC, and the Cl−/HCO3− exchanger, pendrin, mediate NaCl absorption within the cortical collecting duct and the connecting tubule. Although pendrin and ENaC localize to different cell types, ENaC subunit abundance and activity are lower in aldosterone-treated pendrin-null mice relative to wild-type mice. Because pendrin mediates HCO3− secretion, we asked if increasing distal delivery of HCO3− through a pendrin-independent mechanism “rescues” ENaC function in pendrin-null mice. We gave aldosterone and NaHCO3 to increase pendrin-dependent HCO3− secretion within the connecting tubule and cortical collecting duct, or gave aldosterone and NaHCO3 plus acetazolamide to increase luminal HCO3− concentration, [HCO3−], independent of pendrin. Following treatment with aldosterone and NaHCO3, pendrin-null mice had lower urinary pH and [HCO3−] as well as lower renal ENaC abundance and function than wild-type mice. With the addition of acetazolamide, however, acid-base balance as well as ENaC subunit abundance and function was similar in pendrin-null and wild-type mice. We explored whether [HCO3−] directly alters ENaC abundance and function in cultured mouse principal cells (mpkCCD). Amiloride-sensitive current and ENaC abundance rose with increased [HCO3−] on the apical or the basolateral side, independent of the substituting anion. However, ENaC was more sensitive to changes in [HCO3−] on the basolateral side of the monolayer. Moreover, increasing [HCO3−] on the apical and basolateral side of Xenopus kidney cells increased both ENaC channel density and channel activity. We conclude that pendrin modulates ENaC abundance and function, at least in part by increasing luminal [HCO3−] and/or pH.