Na+-K+-ATPase-dependent sodium flux in cortical collecting tubule.
The instantaneous rate of efflux of intracellular Na was studied in rabbit isolated cortical collecting tubules (CCT) as a function of temperature and intracellular Na concentration ([Na]i). [Na]i of microdissected CCT was increased by cold and K-free exposure in the presence of 22Na and the extracellular tracer [3H] sorbitol. [Na]i rose rapidly to 40 mM at 30 min, after which it rose more slowly, reaching 120-140 mM at 6 h. Kinetics of Na efflux were studied after rapid rewarming, using a special device allowing measurements at 20-s intervals. Under control conditions, the total Na load was extruded in less than 8 min, whereas, in the presence of 10(-4) M ouabain, only 50% of the load was extruded during this period of time. Ouabain-sensitive Na efflux was first evident at 13 degrees C and gradually increased between 13 and 35 degrees C. At 37 degrees C, Na+-K+-ATPase-dependent Na efflux was dependent on [Na]i. This efflux gradually increased, from 0.05 to 0.5 peq.nl tubular volume-1.s-1 as a function of [Na]i and reached a plateau at 70 mM [Na]i. It is concluded that [Na]i is a major modulator of the pump activity in CCT; at normal levels of [Na]i, the pump is operating at only a small fraction of its total capacity.
Blot-Chabaud
M
M
Departement de Biologie/Service de Biologie Cellulaire, Institut National de la Santé et de la Recherche Médicale U246, Centre d'Etudes Nucleaires de Saclay, Gif sur Yvette, France.
Jaisser
F
F
Gingold
M
M
Bonvalet
J P
JP
Farman
N
N
D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011817:Rabbits; D012016:Reference Values; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013816:Thermodynamics
D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase