Document Detail

Ouabain-sensitive H,K-ATPase functions as Na,K-ATPase in apical membranes of rat distal colon.
MedLine Citation:
PMID:  10777607     Owner:  NLM     Status:  MEDLINE    
Na,K-ATPase activity has been identified in the apical membrane of rat distal colon, whereas ouabain-sensitive and ouabain-insensitive H,K-ATPase activities are localized solely to apical membranes. This study was designed to determine whether apical membrane Na,K-ATPase represented contamination of basolateral membranes or an alternate mode of H,K-ATPase expression. An antibody directed against the H, K-ATPase alpha subunit (HKcalpha) inhibited apical Na,K-ATPase activity by 92% but did not alter basolateral membrane Na,K-ATPase activity. Two distinct H,K-ATPase isoforms exist; one of which, the ouabain-insensitive HKcalpha, has been cloned. Because dietary sodium depletion markedly increases ouabain-insensitive active potassium absorption and HKcalpha mRNA and protein expression, Na, K-ATPase and H,K-ATPase activities and protein expression were determined in apical membranes from control and sodium-depleted rats. Sodium depletion substantially increased ouabain-insensitive H, K-ATPase activity and HKcalpha protein expression by 109-250% but increased ouabain-sensitive Na,K-ATPase and H,K-ATPase activities by only 30% and 42%, respectively. These studies suggest that apical membrane Na,K-ATPase activity is an alternate mode of ouabain-sensitive H,K-ATPase and does not solely represent basolateral membrane contamination.
V M Rajendran; P Sangan; J Geibel; H J Binder
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  275     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2000 Apr 
Date Detail:
Created Date:  2000-06-02     Completed Date:  2000-06-02     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  13035-40     Citation Subset:  IM    
Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA.
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MeSH Terms
Blotting, Western
Colon / enzymology*
Diet, Sodium-Restricted
Enzyme Inhibitors / pharmacology*
H(+)-K(+)-Exchanging ATPase / chemistry,  physiology*
Membranes / enzymology
Ouabain / pharmacology*
Protein Isoforms
Rats, Sprague-Dawley
Sodium-Potassium-Exchanging ATPase / chemistry,  physiology*
Grant Support
Reg. No./Substance:
0/Enzyme Inhibitors; 0/Protein Isoforms; 630-60-4/Ouabain; EC ATPase; EC ATPase

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