Potassium depletion induces a ouabain-sensitive hco3- reabsorption
in rat renal outer medullary collecting duct : evidence for colonic
h+-k+-atpase activation.
Nakamura, Suguru, Zhaohui Wang, John H. Galla, and Manoocher
Soleimani.
Department of Medicine, University of Cincinnati School of
Medicine, and Veterans Affairs Medical Center, Cincinnati OH,
45267
APStracts 5:0009F, 1998.
To probe the role of the isoforms of H+-K+-ATPase (HKA) in potassium
depletion (KD), rats were placed on a KD diet for 2 weeks. Colonic
(c) HKA mRNA levels increased 30-fold in outer medulla and net HCO3-
flux (JtCO2) in outer medullary collecting duct (OMCD) increased
(13.1 pmol/min-1 /mm tubule length-1 in control to 17.7 in KD,
p<0.01). In normal rats, 1 mM ouabain in perfusate had no effect on
JtCO2 whereas 10 [mu]M Schering 28080 (SCH) decreased JtCO2 to 5.1
(p<0.001). In KD rats, ouabain 1 mM decreased JtCO2 to 6.3
(P<0.001). Although 10 [mu]M SCH also decreased JtCO2 to 4.6
(p<0.001), the inhibitory effects of SCH and ouabain were not
additive. Removal of K+ from perfusate blocked SCH-sensitive JtCO2 in
both normal and KD tubules. The data suggest that, in KD, cHKA is
induced and mediates increased HCO3- reabsorption in OMCD, cHKA in
vivo is sensitive to both SCH and ouabain and cHKA activity is
dominant.
Received 23 July 1997; accepted in final form 5 January 1998.
APS Manuscript Number F246-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 28 January 1998