Hypothalamic corticotropin-releasing factor immunoreactivity is reduced during induction of pituitary tumors by chronic estrogen treatment.
The role that estrogen plays in the regulation of corticotropin-releasing factor (CRF) is not known. A radioimmunoassay specific for rat CRF was utilized to measure the CRF-like immunoreactivity (CRF-ir) in the hypothalamus of ovariectomized rats treated with estradiol for periods up to 12 weeks. Compared to ovariectomized controls, estradiol treatment resulted in significantly reduced CRF-ir after 3 and 12 weeks, although no significant change was seen after 8 weeks. Anterior pituitary (AP) weight was greatly increased by estradiol treatment at all time points studied. Bromocriptine treatment for the last 3 weeks of the 12-week period, or removal of estradiol for 3 weeks after 9 weeks of treatment did not reverse the changes in CRF-ir even though significant regression of tumor size was achieved. There was no correlation between AP weight and CRF-ir in individual animals. These data show that chronic treatment with estrogen reduced hypothalamic CRF-ir content. Neither a direct estrogenic effect or an indirect effect mediated through alterations in the adenohypophysis could be ruled out.
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000473:pathology; D010911:Pituitary Neoplasms / Q000139:chemically induced* / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains
D001971:Bromocriptine; D004958:Estradiol; D003346:Corticotropin-Releasing Hormone