Glucocorticoids and lymphocytes. II. Cell cycle-dependent changes in glucocorticoid receptor content

To study variations in glucocorticoid receptor levels during the cell cycle, we have separated mitogen-stimulated human peripheral lymphocytes and rat lymph node cells by unit gravity sedimentation and measured glucocorticoid binding in the resultant fractions. By morphologic criteria and thymidine incorporation, the fractions were separated into populations of G0 and G1 phase and S and post-S phase cells. A 2- to 3-fold increase in glucocorticoid receptor sites per cell, for cells in the S and post-S phase over those in G0 and G1, was observed with both nonstimulated rat lymph node cell suspensions and concanavalin A-stimulated human peripheral lymphocytes. These observations together with those from other studies indicate that formation of new glucocorticoid receptors near the S phase may be a general phenomenon in proliferating cells. We propose that this increase in glucocorticoid receptors during the cell cycle may explain the increase in glucocorticoid receptors in mitogen-stimulated lymphocytes.