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

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Abstract
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 glucocortoid 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.