Interaction of glucocorticoids with macrophages. Identification of glucocorticoid receptors in monocytes and macrophages

Glucocorticoid binding was measured in resident and thioglycollate- elicited mouse peritoneal macrophages, rabbit alveolar macrophages, and human monocytes. Two assays of binding were used--an assay with intact cells in suspension or monolayers, and an assay of cytosol and nuclear forms of glucocorticoid receptors. The mononuclear phagocytes contained approximately equal to 4--10 X 10(3) high affinity receptor sites per cell, with dissociation constants of approximately equal to 2--8 nM dexamethasone. The binding to the saturable sites was specific for steroids with glucocorticoid or antiglucocorticoid activity. Cortisol, corticosterone, and progesterone competed with dexamethasone for binding, whereas estradiol, dihydrotestosterone, and 11-epicortisol competed very little. Binding of dexamethasone to cytosol and nuclear forms of the receptor complex and temperature-sensitive translocation of cytosol forms to nuclear forms were shown. At 37 degrees C the predominant form of the hormone-receptor complex was nuclear. These results demonstrate that corticosteroids interact with macrophages at physiological concentrations.