Presence of glucocorticoid receptors in cultured thymic epithelial cells

We investigated the presence of glucocorticoid receptors (GC) in human thymic epithelial cells grown in primary cultures and in a pure epithelial rat cell line. These GR levels were compared to those determined concomitantly in fresh human thymocytes. The average number of sites were 54,457/cell for males (n = 8) and 58,224/cell for females (n = 8) with mean Kd values of 1.5 and 1.7 X 10(-8) M, respectively, in cultured human epithelial cells. These results are comparable to those obtained for rat thymic epithelial cells. Competition experiments showed that the relative affinities of the steroids tested were in decreasing order: dexamethasone greater than progesterone greater than testosterone and estradiol. This observation is compatible with binding to physiological GR. Moreover, the mean GR value appeared to be approximately 10 times higher for human thymic epithelial cells than for thymocytes. Thus, human epithelial cells as well as thymocytes should be considered as a specific target for glucocorticoid hormones.