Characterization and localization of ouabain-insensitive Na-dependent ATPase activities along the rat nephron.
Single segments of rat nephron contain two distinct ouabain-insensitive, K-independent, Na-dependent ATPase activities: a Na-stimulated ATPase and a Na-inhibited ATPase. Na-inhibited ATPase activity is found in the proximal tubule and the thick ascending limb of Henle's loop but is absent in the collecting tubule whereas Na-stimulated ATPase is exclusively located in the proximal convoluted tubule. Na-inhibited ATPase, but not Na-stimulated ATPase, is totally abolished in the presence of 100 microM Ca2+. Conversely, Na-stimulated ATPase, but not Na-inhibited ATPase, is curtailed when nephron segments are preincubated at pH 7.2 whereas it is activated at pH 7.8. Finally, Na-stimulated ATPase displays an apparent Km for Na+ of approximately 10 mM, and is dose-dependently inhibited by the diuretic triflocin (IC50 approximately 6 x 10(-6) M).
el Mernissi
G
G
Laboratoire des Biomembranes, Faculté des Sciences, Université Cadi Ayyad, Marrakech, Morocco.
Barlet-Bas
C
C
Khadouri
C
C
Marsy
S
S
Cheval
L
L
Doucet
A
A
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008297:Male; D003012:Microbial Collagenase / Q000494:pharmacology; D009399:Nephrons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology*
D012965:Sodium Chloride; D010042:Ouabain; D003012:Microbial Collagenase; D000251:Adenosine Triphosphatases; D002122:Calcium Chloride