Glucocorticoid and mineralocorticoid receptors for aldosterone

Specific binding of aldosterone and dexamethasone by rat kidney and hepatoma tissue culture (HTC) cell cytosol has been studied. In cytosol of HTC cells, aldosterone and dexamethasone bind to a single class of sites with affinities that correspond with their potencies as inducers of tyrosine aminotransferase. Kidney cytosol, however, contains two classes of specific aldosterone binding sites. The higher affinity sites bind aldosterone with an affinity (equilibrium, dissociation, constant) which is similar to the plasma concentration of aldosterone required for antinatriuresis. The lower affinity aldosterone-binding sites are present at a higher concentration than the higher affinity sites and also bind dexamethasone with a high affinity. We have tentatively identified these two classes of binding sites in renal cytosol as "mineraloeonicoid" and "glucocorticoid" receptors, respectively.