Characterization of specific corticosterone binding sites in adrenal cortex plasma membrane and their localization by autoradiographic studies

Abstract

Specific corticosterone binding to calf adrenal cortex plasma membrane was measured using the biologically active radioligand [3H]corticosterone. Corticosterone binding was found to be time-dependent, saturable and reversible, and was reduced by more than 70% when membranes were pretreated with proteases. The population of corticosterone binding sites in calf adrenal cortex plasma membrane was homogeneous and displayed the following characteristics: equilibrium dissociation constant Kd = 77 +/- 8 nM and maximum specific binding capacity Bmax = 70,378 +/- 6,385 fmol/mg protein. The relative affinities of several structural analogues of steroids were deduced from competition assays. From these experiments we can conclude that the plasma membrane binding site characterized is selective for corticosterone and progesterone derivatives, and different from nuclear glucocorticoid, mineralocorticoid, estrogen and progestin receptors. Likewise, this corticosterone binding site is independent of mineralocorticoid and Na+, K(+)-ATPase digitalis receptors. From autoradiographic studies we suggest these corticosterone binding sites are located in the whole adrenal cortex.

Rapid non‐genomic inhibition of ATP‐induced Cl− secretion by dexamethasone in human bronchial epithelium

“…However, aldosterone and dexamethasone do not display a high affinity for this membrane receptor. Other putative membrane binding sites for glucocorticoids have been detected in mouse and rat liver, rat kidney, rat brain and calf adrenal cortex (Ibarrola et al 1991; Trueba et al 1991; Guo et al 1995; Andres et al 1997).…”

Astroglia-Microglia Cross Talk during Neurodegeneration in the Rat Hippocampus

“…Glucocorticoid receptors were labelled with 10 nM [ 3 H]corticosterone (79 Ci/mmol) added to a buffer solution containing 20 mM Tris-HCl (pH 7.4), 1.5 mM EDTA, 140 mM NaCl, and 5 mM glucose. 5 μ M RU-28362 was used to discriminate between GR and mineralocorticoid receptor specific [ 3 H]corticosterone binding [ 34 ]. The nonspecific binding was determined by incubation with 20 μ M corticosterone and was lower than 20% of total binding.…”