Receptor occupancy vs. induction of Na+-K+-ATPase and Na+ transport by aldosterone

Am J Physiol. 1985 Jan;248(1 Pt 1):C102-8. doi: 10.1152/ajpcell.1985.248.1.C102.


In the urinary bladder of the toad Bufo marinus aldosterone (between 0.8 and 100 nM) stimulates Na+ transport [half-maximal induction concentration (K1/2) = 6.5 nM]. At low hormone concentrations (0.8-8 nM), the increase of Na+ transport between 0.75 and 2.5 h is accompanied by a fall in transepithelial resistance (R). Higher hormone concentrations (30-800 nM) induce an additional resistance-independent fraction of Na+ transport within 2.5-8 h. From 6 h on, aldosterone (between 0.2 and 20 nM) stimulates in the same tissue the biosynthesis rate of the alpha- and beta-subunits of Na+-K+-ATPase (K1/2 = 3 and 1.5 nM, respectively). New pump synthesis is thus not a prerequisite for the early mineralocorticoid response but might be linked to the late transport event. The mineralocorticoid response is usually ascribed to interaction with the higher affinity type 1 receptor. In the present study we show, however, that at least 55% of the overall Na+ transport response is linked to nuclear occupation of the lower affinity type 2 receptors [dissociation constant (Kd) = 50 nM, maximum number of binding sites (Nmax) = 315 fmol/mg protein]. Distinct aldosterone effects, such as the fall in R and the increase in Na+-K+-ATPase synthesis, are more closely related to occupation of type 1 receptors (Kd = 0.3 nM, Nmax = 23 fmol/mg protein). At maximal induction of these latter parameters, only about 20% of type 2 receptors are occupied. These results suggest that both types of aldosterone receptors are involved in the mediation of the full mineralocorticoid response: type 1 in the early and late and type 2 particularly in the late tissue response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldosterone / metabolism
  • Aldosterone / pharmacology*
  • Androstanols / pharmacology
  • Animals
  • Biological Transport, Active / drug effects
  • Bufo marinus
  • Enzyme Induction
  • Kinetics
  • Receptors, Glucocorticoid / metabolism*
  • Receptors, Mineralocorticoid
  • Receptors, Steroid / metabolism*
  • Sodium / metabolism*
  • Sodium-Potassium-Exchanging ATPase / biosynthesis*
  • Urinary Bladder / drug effects
  • Urinary Bladder / metabolism*


  • Androstanols
  • Receptors, Glucocorticoid
  • Receptors, Mineralocorticoid
  • Receptors, Steroid
  • Aldosterone
  • RU 26988
  • Sodium
  • Sodium-Potassium-Exchanging ATPase