Regulation of renal Na+,K(+)-ATPase in rat thick ascending limb during K+ depletion: evidence for modulation of Na+ affinity.
1. NaCl reabsorption along the loop of Henle is reduced in K(+)-depleted rats. Because Na+,K(+)-ATPase energizes this transport and because K+ depletion is known to induce an upregulation of Na+,K(+)-ATPase in most tissues, the regulation of this enzyme was investigated at the level of single thick ascending limbs of the loop of Henle freshly microdissected from rats fed either a normal (control rats) or a low-K+ diet (LK rats). 2. Within 2 weeks of K+ depletion, Na+,K(+)-ATPase activity and [3H]ouabain binding were increased by 30-50% in the medullary portion of the thick ascending limb (MTAL). 3. Despite this increase in the number of Na+,K(+)-ATPase units, the transport capacity of the Na+,K+ pump, determined by ouabain-sensitive Rb+ uptake in the presence of an extracellular concentration of Rb+ mimicking the kalaemia determined in control (4.0 mM Rb+) and LK rats (2.3 mM Rb+), was reduced in MTAL from LK rats. 4. Inhibition of the Na+,K+ pump was not accounted for by changes in either extracellular K+ or intracellular Na+ concentrations, but by a decrease in the pump affinity for Na+. 5. Because this change in the apparent affinity of the Na+,K+ pump for Na+ was detectable in intact but not in permeabilized MTAL cells, it is probably induced by a rapidly reversible cytosolic factor.
Buffin-Meyer
B
B
Laboratoire de Physiologie Cellulaire, Collège de France, Paris.
Marsy
S
S
Barlet-Bas
C
C
Cheval
L
L
Younes-Ibrahim
M
M
Rajerison
R
R
Doucet
A
A
D000818:Animals; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D013997:Time Factors
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium