Biochemical and functional characterization of H(+)-K(+)-ATPase in distal amphibian nephron.
Because proton secretion and K+ reabsorption in the late distal tubule of amphibians are active, we evaluated whether these processes could be mediated by an H(+)-K(+)-ATPase similar to the gastric H(+)-K+ pump and to the K(+)-ATPase previously described in the terminal segments of the mammalian nephron. K(+)-stimulated ATPase activity was detected in microdissected segments of frog and Necturus nephron: its activity was high in the late distal and collecting tubules, whereas it was undetectable in the proximal convoluted tubule and early distal tubule. In frog collecting tubule, K(+)-ATPase had a high affinity for K+ (Km approximately 0.30 mM), was inhibited by vanadate, omeprazole, and the imidazopyridine Sch 28080, and was insensitive to ouabain. Furthermore, in vivo administration of Sch 28080 to anesthetized Necturus induced a significant rise of the steadystate intratubular pH in the late distal tubule, demonstrating that this drug inhibited tubular fluid acidification. It is suggested that K(+)-ATPase present in the terminal segments of amphibian nephron is similar to the gastric H(+)-K+ pump and is involved in urinary acidification.
Planelles
G
G
Laboratoire de Physiologie Rénale, Institut National de la Santé et de la Recherche Médicale Unité 323, Centre Hospitalier Universitaire Necker, Paris, France.
Anagnostopoulos
T
T
Cheval
L
L
Doucet
A
A
D000251:Adenosine Triphosphatases / Q000032:analysis* / Q000502:physiology; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D017506:H(+)-K(+)-Exchanging ATPase; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology; D007686:Kidney Tubules, Distal / Q000737:chemistry* / Q000201:enzymology / Q000502:physiology; D008845:Microinjections; D009338:Necturus maculosus / Q000502:physiology*; D009853:Omeprazole / Q000494:pharmacology; D011895:Rana ridibunda / Q000502:physiology*; D014638:Vanadates / Q000494:pharmacology
D000897:Anti-Ulcer Agents; D007093:Imidazoles; C035235:Sch 28080; D014638:Vanadates; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole