K(+)-ATPase-mediated Rb+ transport in rat collecting tubule: modulation during K+ deprivation.
To evaluate the involvement of K(+)-ATPase activity in K+ transport in the terminal segments of the rat nephron, we searched for the existence of a component of Rb+ uptake into microdissected segments of collecting tubule associated with the activity of this ATPase. Results indicated that K(+)-ATPase is stimulated by K+ and by Rb+ in a similar fashion and that it is specifically inhibited by the imidazopyridine Sch 28080 (apparent affinity approximately 5 x 10(-7) M). In both cortical and outer medullary collecting tubules (CCT and MCT) of normal rats, 10(-4) M Sch 28080 significantly inhibited the initial rate of Rb+ uptake. Sch 28080-sensitive Rb+ uptake in these two nephron segments was not altered by ouabain, as K(+)-ATPase activity. Finally, both K(+)-ATPase activity and Sch 28080-sensitive Rb+ uptake were increased by similar factors in the CCT and MCT of rats fed a K(+)-depleted diet for 3 days. In these two nephron segments, the apparent stoichiometry of K(+)-ATPase was 1 Rb+:1 ATP. These results demonstrate that K(+)-ATPase reflects the activity of a K+ pump that is pharmacologically similar to the gastric H(+)-K+ pump.
Cheval
L
L
Laboratoire de Physiologie Cellulaire, Unité de Recherche Associée 219, Centre National de la Recherche Scientifique, Collège de France, Paris.
Barlet-Bas
C
C
Khadouri
C
C
Feraille
E
E
Marsy
S
S
Doucet
A
A
D000251:Adenosine Triphosphatases / Q000502:physiology*; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D027682:Cation Transport Proteins; D007093:Imidazoles / Q000494:pharmacology; D007685:Kidney Tubules, Collecting / Q000378:metabolism / Q000502:physiology*; D008297:Male; D011188:Potassium / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism / Q000493:pharmacokinetics*
D000897:Anti-Ulcer Agents; D027682:Cation Transport Proteins; D007093:Imidazoles; C035235:Sch 28080; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D012413:Rubidium; D011188:Potassium