Mineralocorticoid (Type I) receptors in the olfactory mucosa of the mammal: Studies with [³H]Aldosterone and the anti-mineralocorticoid spironolactone

High-affinity, specific binding sites to mineralocorticoids, with characteristics of mineralocorticoid (type I) receptors, have been found in the mammalian olfactory mucosa. In the presence of RU 28362, which blocks low-affinity binding of the labeled hormone to glucocorticoid (type II) receptors, Scatchard analysis of the specific [³H]aldosterone binding indicates that aldosterone binds to a single class of high-affinity (type I) sites with a dissociation constant, K(d(r)), of 1.2 x 10^-9 M and a maximum number of binding sites, B(max), of 63 fmol/mg dry tissue. Time course of association of [³H]aldosterone and its binding sites showed maximal binding by 30 min at 25°C which remained unchanged up to 90 min. Competition studies performed with 1 x 10^-7-1 x 10^-5 M spironolactone, a competitive mineralocorticoid antagonist, showed a dose-response reduction of [³H]aldosterone binding, implying that in the olfactory mucosa this compound behaves as an aldosterone antagonist. These results demonstrate significant [³H]aldosterone binding to receptors of high affinity and mineralocorticoid-specificity and suggest that the olfactory mucosa is a target site for mineralocorticoid action.