A whole-cell assay for glucocorticoid binding sites in normal human lymphocytes.

We established a whole-cell assay in the clinical laboratory, using normal human lymphocytes isolated from peripheral blood. [3H]Dexamethasone binding reached a maximum after 90 min at 24 degrees C. Dissociation constants (Kd) were determined to be 1 X 10(-9) mol/L. Specific glucocorticoid-binding capacities of 3 to 23 fmol/10(6) cells, or 1800 to 13 800 sites/cell, were observed. Steroids with glucocorticoid activity such as triamcinolone acetonide and cortisol effectively competed for [3H]dexamethasone binding sites, whereas those with no glucocorticoid potency such as estradiol-17 beta and testosterone showed little inhibition. Studies on the cellular distribution of [3H]dexamethasone indicated that 23% was bound to the cytosol, 77% to the cell nucleus. The whole-cell assay is easily adaptable for the clinical laboratory assessment of glucocorticoid receptors in normal and malignant lymphocytes, and may be useful in evaluating the activity-function relationships of potential therapeutic agents.