The Relationship between Glucocorticoid Binding and Tyrosine Aminotransferase Induction in Hepatoma Tissue Culture Cells

Glucocorticoid receptors with many properties suggesting their involvement in the hormonal induction of tyrosine aminotransferase have been detected in rat hepatoma tissue culture cells. These „specific receptors” approach saturation as the steroid concentrations required for maximal induction are reached. Inducer analogs influence cortisol binding to the specific receptors in direct relation to their influence on cortisol induction. The inducer association with and dissociation from specific receptors are rapid enough to account for the kinetics of induction and deinduction. Chromatographic studies suggest the specific receptors bind unaltered dexamethasone and cortisol. „Nonspecific” association of steroids with the cells also occurs and can be distinguished from specific binding.