Characterization of human spleen tumor glucocorticoid receptors using [3H]cortisol as ligand.

The present report describes an assay system allowing the quantification and characterization of [3H]cortisol binding to glucocorticoid receptors in bloodrich human tissue. The essence of this assay lies in the selective binding of 17 beta-carboxylic acids of natural corticoids to corticosteroid binding globulin (CBG). In the presence of 1240 nmol/l 11 beta-hydroxy-3-oxo-4-androstene-17 beta-carboxylic acid only glucocorticoid receptors were detectable with the expected properties: high affinity for synthetic and natural glucocorticoids, but failure to bind to the respective 17 beta-carboxylic acids, apparent Kd's at 0-4 degrees C for [3H]cortisol of approx 30 nmol/l, Nmax similar to those determined with [3H]dexamethasone and the typical sequence of relative binding affinities (dexamethasone greater than cortisol greater than progesterone greater than 17 beta-methyl-testosterone, estradiol).