Sodium-independent in vitro induction of Na+,K+-ATPase by aldosterone in renal target cells: permissive effect of triiodothyronine.
The aim of this study was to develop an in vitro system in which we could study the causal relationship between short-term stimulation of Na+,K+-ATPase in the collecting tubule by aldosterone on the one hand and protein synthesis and changes in intracellular Na+ concentration on the other hand. Previous in vivo studies suggested that triiodothyronine might facilitate aldosterone-induced stimulation of Na+,K+-ATPase. Results show that when segments of cortical collecting tubules microdissected from collagenase-treated kidneys of adrenalectomized rats were incubated for 3 hr in the presence of either 10(-8) M aldosterone or 10(-8) M triiodothyronine alone Na+,K+-ATPase activity was not altered, whereas the addition of both hormones markedly stimulated the activity and the number of catalytic sites of Na+,K+-ATPase. This stimulation was abolished by actinomycin D and cycloheximide, whereas it was not altered in the absence of extracellular sodium or in the presence of the luminal Na+-channel blocker amiloride. Thus, triiodothyronine facilitates the in vitro induction of Na+,K+-ATPase synthesis by aldosterone. Aldosterone action on Na+,K+-ATPase is independent of Na+ availability.
Barlet-Bas
C
C
Laboratoire de Physiologie Cellulaire, Collège de France, Paris.
Khadouri
C
C
Marsy
S
S
Doucet
A
A
D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D010042:Ouabain / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*; D014284:Triiodothyronine / Q000494:pharmacology*
D014284:Triiodothyronine; D000450:Aldosterone; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase