Effects of D- and L-thyroxine on the glucocorticoid binding capacity of adult rat liver

Abstract

Administration of either D- or L-thyroxine (T 4) significantly increased the glucocorticoid binding capacity of cytosol of the livers of adrenalectomized adult rats. Administration of up to 0.5 mg/100 g body wt. of L-T 4 was more effective than that of D-T 4, but higher doses (0.8–3 mg/100 g body wt.) of D-T 4 increased the binding capacity markedly to more than that with L-T 4. T 4-administration did not alter the apparent dissociation constant of glucocorticoid binding proteins for glucocorticoid binding, or their behavior on DEAE-cellulose chromatography either before or after thermal activation (23°C for 40 min). Thus the increased binding capacity seemed to be due to increase in the level of glucocorticoid receptor in rat liver.