Regulatory effects of epidermal growth factor and retinol on the glucocorticoid receptor level in cultured chick embryonic skin

When undifferentiated skin from 13-day-old chick embryos was cultured in a chemically defined medium, glucocorticoid specifically decreased the dexamethasone-binding activity of the epidermal cytosol after 1 day of culture, 3 days before it induced formation of a cornified layer over the intermediate cells of the epidermis. The binding activity reappeared after removal of the steroid from the medium. This reappearance was inhibited by epidermal growth factor (EGF, 100 ng/ml). The Addition of 2 microM retinol resulted in a 3-fold increase in specific dexamethasone binding in the epidermal cytosol within 12 h with no change in the binding affinity. The inhibition of glucocorticoid-induced keratinization by retinol is due a to mechanism other than inactivation of the glucocorticoid receptor.