Steroid hormone receptors in normal human lymphocytes. Induction of glucocorticoid receptor activity by phytohemagglutinin stimulation

The presence of specific steroid hormone receptors in human lymphocytes was investigated in unstimulated and phytohemagglutinin stimulated glass wool column purified peripheral blood lymphocytes. Specific steroid binding in intact cells was determined by a whole cell competitive binding assay. Non phytohemagglutinin stimulated lymphocytes had about 2700 specific glucocorticoid binding sites per cell; phytohemagglutinin stimulation induced a 2 to 3 fold increase in glucocorticoid receptor activity within 16h of culture. No estrogen, androgen, or progestin binding sites were detected in either unstimulated or phytohemagglutinin stimulated peripheral blood lymphocytes. Scatchard analysis of glucocorticoid binding was consistent with a single class of receptor sites with a dissociation constant (Kd) of about 5.5x10^-9 M (correlation coefficient r=-0.96). Significant competition for radiolabeled dexamethasone binding was not observed with steroids lacking glucocorticoid activity. There was good agreement between relative binding affinities of various steroids to glucocorticoid receptor in lymphocytes and ability of these steroids to inhibit phytohemagglutinin stimulated thymidine incorporation.