Glucocorticoid Receptors of Human Mononuclear Leukocytes<i>in Vitro</i>*

Abstract

The present study was performed to analyze glucocorticoid receptor binding in peripheral blood mononuclear leukocytes from normal adult humans. In addition, the potential regulatory effect of excess amounts of glucocorticoids and thyroid hormones on glucocorticoid receptor binding was investigated. A whole cell binding assay with [3H]dexamethasone (3H-labeled 9 alpha-fluoro-11 beta, 17 alpha, 21-trihydroxy-16 alpha-methyl-pregna-1,4-diene-3,20-dione) was used. Binding parameters were estimated by means of unweighted nonlinear regression analysis, using the free ligand concentration as the independent variable and the ratio of bound to free ligand at steady state as the dependent variable. The dissociation constant (Kd) at 30 C was 5.5 +/- 1.4 nM (mean +/- SD; n = 57) compared to 10.5 +/- 4.8 nM (n = 16) at 37 C. The numbers of receptors per cell were not affected by temperature and were 7400 +/- 1560 and 7180 +/- 2710, respectively. The number and affinity of glucocorticoid receptors did not differ between women and men. Receptor binding did not change in subjects ranging in age from 18-63 yr. Moreover, no diurnal or seasonal variations were recorded. Cells from five pregnant women in the last trimester showed decreased receptor affinity (Kd at 30 C = 7.7 +/- 1.4 nM; P less than 0.01) and increased receptor number (8950 +/- 870; P less than 0.05). Six patients with untreated thyrotoxicosis had normal receptor binding. No change in receptor number or affinity (30 C) was found in cells from three patients with Cushing's disease and four prednisone (17 alpha,21-dihydroxy-pregna-1,4-diene-3,11,20-trione)-treated asthmatics. These data indicate a widespread invariability of glucocorticoid receptors of human mononuclear leukocytes and do not support the theory of a regulatory role of excess glucocorticoids on their own receptor number or affinity.