Ouabain-sensitive and -insensitive K-ATPases in rat nephron: effect of K depletion.
Because a ouabain-sensitive H-K-adenosinetriphosphatase (H-K-ATPase) has been identified recently in the amphibian bladder, we evaluated whether such an ATPase might exist also in the mammalian kidney, along with the ouabain-insensitive H-K-ATPase previously described in the collecting duct. For this purpose, we searched for an Na-independent, K-stimulated, ouabain- and Sch-28080-inhibitable ATPase activity in single segments of rat nephron. Ouabain-sensitive K-stimulated ATPase activity was detected in the absence of Na+ in rat proximal convoluted and straight tubules and in medullary and cortical thick ascending limbs of Henle's loop but not in collecting ducts. This K-ATPase differs from Na-K-ATPase by 1) its absence of requirement for Na, 2) its sensitivity to Sch-28080, 3) its higher sensitivity to ouabain, and 4) its absence in the collecting duct. It differs from the collecting duct H-K-ATPase by 1) its distribution along the nephron, 2) its sensitivity to ouabain, and 3) its lower sensitivity to Sch-28080. Furthermore, in rats fed a K-depleted diet for 2 wk, ouabain-sensitive K-ATPase activity was markedly reduced in both proximal tubules and thick ascending limbs, whereas collecting duct H-K-ATPase was upregulated.
Younes-Ibrahim
M
M
Laboratoire de Biologie Intégrée des Cellules Rénales, Centre National de la Recherche Scientifique, Collège de France, Paris, France.
Barlet-Bas
C
C
Buffin-Meyer
B
B
Cheval
L
L
Rajerison
R
R
Doucet
A
A
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D002024:Bufo marinus; D027682:Cation Transport Proteins; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007684:Kidney Tubules / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D009399:Nephrons / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D001743:Urinary Bladder / Q000201:enzymology
D027682:Cation Transport Proteins; D007093:Imidazoles; D007527:Isoenzymes; C035235:Sch 28080; D010042:Ouabain; D011189:Potassium Chloride; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase