Differential regulation of putative k-atpase by low k diet and
corticosteroids in rat distal colon and kidney.
Jaisser, F., B. Escoubet, N. Coutry, E. Eugene, J. P. Bonvalet, and N.
Farman.
Institut National de la Sante et de la Recherche Medicale, U246 and
U426, Institut Federatif de Recherches "Cellules
epitheliales", Faculte de Medecine Xavier Bichat, BP 416 - 75870
PARIS Cedex 18 - France
APStracts 2:0323C, 1995.
Potassium homeostasis depends on potassium absorption in digestive and
renal epithelia. Recently a cDNA encoding for a putative K+-ATPase
[alpha] subunit has been characterized. We studied its expression by
RNAse Protection Assay and In Situ Hybridization in the distal colon
and the kidney of rats in various physiological states. In the distal
colon of control rats, high expression of the colonic putative K+
-ATPase mRNA was restricted to the surface epithelial cells. Low K+
diet did not modify this expression ; adrenalectomy decreased it, and
both aldosterone or dexamethazone 2 days treatment restored normal
levels. In the kidney of control rats, levels of K+-ATPase mRNA were
very low. Low K+ diet revealed a clear mRNA expression, consistent
with a recent report (J.A Kraut et al, Am.J.Physiol. 1995,268,F581
-F587). This expression was restricted to the outer medullary
collecting duct, presumably in principal cells. Changes in
corticosteroid status did not influence the renal expression. Our
results, together with previous studies on K+ absorption and K+
-ATPase activity suggest that more than a single molecular form of K+
-ATPase is likely to be responsible for the regulation of K+
absorption in both colon and distal nephron.
Received 4 April 1995; accepted in final form 25 August 1995.
APS Manuscript Number C192-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.