Molecular identification of Sch28080-sensitive K-ATPase activities in the mouse kidney.
Rat collecting ducts display either an ouabain-insensitive or an ouabain-sensitive K-ATPase activity inhibited by Sch28080 according as animals are fed a normal or a potassium-depleted diet (types I and III K-ATPase, respectively). Two isoforms of H,K-ATPase have been cloned from rat gastric mucosa and colon, respectively. Gastric and colonic H,K-ATPase are expressed in the kidney, suggesting that they might account for types I and III K-ATPases. However, this hypothesis is not fully supported by segmental expression of gastric and colonic H,K-ATPase along the rat collecting duct, as well as by comparison of the pharmacological properties of gastric and colonic H,K-ATPase expressed in Xenopus ovocyte and types I and III K-ATPases in rat collecting ducts. The aim of the present work is to address directly the molecular origin of types I and III K-ATPases in the mouse collecting duct by measuring K-ATPase activities in collecting ducts of wild-type mice and mice genetically deficient in either gastric or colonic H,K-ATPase fed either a regular or a potassium-depleted diet. Like the rat, mouse collecting ducts display type I or III K-ATPase activity when fed a regular or a potassium-depleted diet, respectively. Type I K-ATPase activity is detected in colonic H,K-ATPase-deficient mice but not in gastric H,K-ATPase-deficient animals. Conversely, type III K-ATPase activity disappears in colonic H,K-ATPase-deficient but not in gastric H,K-ATPase-deficient mice. In conclusion, types I and III K-ATPases measured in collecting ducts of normal and potassium-depleted mice reflect the functional expression of gastric and colonic H,K-ATPase, respectively.
Dherbecourt
Olivier
O
Laboratoire de Physiologie et Génomique Rénales, Unité Mixte de Recherche CNRS/UPMC 7134, IFR 58, Institut des Cordeliers, 15 Rue de l'Ecole de Médecine, 75270 Paris Cedex 6, France.
Cheval
Lydie
L
Bloch-Faure
May
M
Meneton
Pierre
P
Doucet
Alain
A
D000818:Animals; D003106:Colon / Q000201:enzymology; D004032:Diet; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology*; D007668:Kidney / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D011188:Potassium / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D013270:Stomach / Q000201:enzymology
D007093:Imidazoles; D021122:Protein Subunits; C035235:Sch 28080; D017506:H(+)-K(+)-Exchanging ATPase; D011188:Potassium