Estrogen-Induced Decrease of Glucocorticoid Receptor Messenger Ribonucleic Acid Concentration in Rat Anterior Pituitary Gland

Using Northern blots and hybridization techniques, we have identified an approximately 6.5 kilobase glucocorticoid receptor mRNA species in rat anterior pituitary gland. Ovariectomy resulted in an approximately 2-fold increase in glucocorticoid receptor mRNA concentrations. This effect was maximal 8 days after surgery and glucocorticoid receptor mRNA levels remained elevated for at least up to 4 weeks. Administration of 17-beta-estradiol completely reversed the ovariectomy-induced increase in glucocorticoid receptor mRNA content of pituitary gland. Treatment of rats with corticosterone did not influence the ovariectomy-induced increase in glucocorticoid receptor mRNA content, indicating that this increase is not mediated via effects on circulating glucocorticoid levels or availability. In situ hybridization experiments confirmed the ovariectomy-induced increase in glucocorticoid receptor mRNA content and indicated that this action is widely distributed throughout the anterior pituitary gland.