AJP - Renal Physiology, Vol 260, Issue 6 806-F812, Copyright © 1991 by American Physiological Society

ARTICLES

Biochemical and functional characterization of H(+)-K(+)-ATPase in distal amphibian nephron

G. Planelles, T. Anagnostopoulos, L. Cheval and A. Doucet
Laboratoire de Physiologie Renale, Institut National de la Sante et de la Recherche Medicale Unite 323, Centre Hospitalier Universitaire Necker, Paris, France.

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.

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