Regulation of the glucocorticoid receptor in human lymphocytes

The presence of a glucocorticoid receptor in human lymphocytes is well established, but factors affecting its regulation have not been described. Using a competitive binding whole cell assay, we have examined the binding of [3H]-dexamethasone at 24 and 37 degrees C in untreated normal subjects and in healthy subjects taking various glucocorticoid preparations. At 24 degrees C normal human lymphocytes had 6000 binding sites/cell and a dissociation constant of 4 x 10(-9) M. The administration of 1 mg of dexamethasone, 5 mg of prednisone, and 37.5 mg of cortisone acetate resulted in a 30% decrease in binding sites after 1 week with no change in binding affinity. No changes in the number of binding sites was noted before 1 week and the diminished number persisted for 1 week after discontinuation of glucocorticoid treatment. Lymphocytes from hospitalized patients taking 40-60 mg of dexamethasone daily demonstrated the same change in number of binding sites that was seen in normal subjects taking 1 mg of dexamethasone. When binding assays were carried out at physiologic temperature there was the same decrease in number of binding sites after dexamethasone administration, and in addition, there was a two-fold increase in binding affinity. Glucocorticoid administration results in a time-dependent decrease in the number of lymphocyte glucocorticoid binding sites that is independent of the type of glucocorticoid administered. This is the first in vivo demonstration that glucocorticoids modulate their own receptors in man.