Regulation of colonic h,k-atpase in large intestine and kidney by dietary na depletion and dietary k depletion. Sangan, Pitchai, Vazhaikkurichi M. Rajendran, Andrea S. Mann, Michael Kashgarian, and Henry J. Binder. The Departments of Internal Medicine and Pathology, Yale University School of Medicine, New Haven, Connecticut 06510, USA
APStracts 3:0309C, 1996.
Active potassium absorption in the rat distal colon is energized by an apical membrane H,K-ATPase while potassium absorption in the distal collecting duct is generally believed to be modulated by a related renal H,K-ATPase. Experiments were performed to establish the mechanism(s) by which dietary Na-depletion (with resulting elevated aldosterone levels) and K-depletion stimulate K absorption. Colonic H,K-ATPase specific cDNA probe and a polyclonal antibody were utilized to measure mRNA (Northern blot analyses) and protein (Western blot and immunofluorescence studies) abundance in distal and proximal colon and renal collecting ducts and cortex of dietary Na -depleted and K-depleted rats. Dietary Na-depletion, but not K -depletion upregulated H,K-ATPase specific mRNA and protein expression in distal and proximal colon; Na-depletion also stimulated H,K-ATPase activity in distal colon. In contrast to distal colon, H,K-ATPase specific protein level in the outer medulla was enhanced by dietary K-depletion, but not by Na-depletion. This study establishes that 1) dietary sodium depletion stimulates colonic H,K-ATPase activity most likely by a transcriptional process; 2) the regulation of colonic H,K-ATPase expression by dietary sodium depletion and dietary potassium depletion is not identical in the large intestine and differs in the kidney from colon suggesting the presence of two (or more) H,K-ATPase isoforms in the rat colon. 

Received 8 July 1996; accepted in final form 13 September 1996.
APS Manuscript Number C379-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996