Regulation of Na+, K(+)-ATPase in the rat outer medullary collecting duct during potassium depletion.
Because in outer medullary collecting ducts (OMCD) of K(+)-depleted rats, K+ secretion is abolished, whereas Na+, K(+)-ATPase, which energizes this secretion, is markedly stimulated, it has been proposed that Na+, K(+)-ATPase was mislocated to the apical cell membrane and energized K+ reabsorption. This hypothesis has been supported by paradoxical effects of ouabain in K(+)-depleted compared with normal rats. However, we have recently shown that ouabain inhibits not only Na+, K(+)-ATPase but also apical H+, K(+)-ATPase in the OMCD of K(+)-depleted rats. Therefore, this study was designed to evaluate whether previous observations were accounted for by Na+, K(+)-ATPase or by ouabain-sensitive H+, K(+)-ATPase. Na+, K(+)-ATPase was distinguished from H+, K(+)-ATPase by its insensitivity to Sch-28080. Results indicate that the hydrolytic and transport activities of Na+, K(+)-ATPase, the number of its functional units, and the expression of mRNA of its alpha 1 and beta 1 subunits were increased threefold or more in the OMCD of rats fed a K(+)-depleted diet for 2 wk. By immunofluorescence, Na+, K(+)-ATPase staining was strongly increased in K(+)-depleted rats but remained localized to the basolateral pole of OMCD principal cells. In conclusion, K+ depletion is associated with marked induction of functional Na+, K+ pumps at the basolateral pole of rat OMCD. Therefore, reduced K+ secretion might result from inhibition of apical K+ conductances and stimulation of basolateral K+ recycling. It is proposed that increased Na+, K(+)-ATPase participates in the increased Na+ reabsorption prevailing in collecting ducts of K(+)-depleted rats.
Buffin-Meyer
B
B
Laboratoire de Biologie Intégrée des Cellules Rénales, Service de Biologie Cellulaire, Centre d'Etudes de Saclay, Gif sur Yvette, France.
Verbavatz
J M
JM
Cheval
L
L
Marsy
S
S
Younes-Ibrahim
M
M
Le Moal
C
C
Doucet
A
A
D000818:Animals; D001483:Base Sequence; D046508:Culture Techniques; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D019084:Fluorescent Antibody Technique, Indirect; D017506:H(+)-K(+)-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects / Q000201:enzymology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D010042:Ouabain / Q000008:administration & dosage; D016133:Polymerase Chain Reaction; D011191:Potassium Deficiency / Q000201:enzymology*; D017419:Potassium, Dietary; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D015854:Up-Regulation
D004791:Enzyme Inhibitors; D017419:Potassium, Dietary; D010042:Ouabain; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase