Immunoreactive dynorphin is regulated by estrogen in the rat anterior pituitary.
The pituitary and hypothalamic content of dynorphin was determined by radioimmunoassay and characterized by high-performance liquid chromatography (HPLC) in adult female Sprague-Dawley rats, intact and ovariectomized with and without estrogen treatment. Animals were given estradiol benzoate, or vehicle (oil) by six daily intramuscular injections. Anterior pituitary content of immunoreactive (ir)-dynorphin in ovariectomized rats was approximately twice that of intact animals, and consisted of a single HPLC peak co-eluting with dynorphin 32. Administration of estradiol benzoate (0.06-6 micrograms/day) caused a marked decrease of ir-dynorphin in the anterior lobe of castrate female rats, with a half-maximal effect at 0.2 microgram/day; levels were restored to those seen in intact animals with 6 micrograms estradiol benzoate per day, an effect which was not influenced by concomitant administration of progesterone (1 mg/day), or bromocriptine (100 micrograms/day). In the hypothalamus and neuro-intermediate lobe multiple peaks of immunoreactive dynorphin were seen, coeluting with dynorphin A 1-8, dynorphin A 1-17 and dynorphin 32. Neither castration nor estrogen treatment altered ir-dynorphin content in these tissues. These findings suggest that the ovary exerts a specific modulating influence on AP ir-dynorphin in the rat, and that in addition this inhibition appears to be mediated by ovarian estrogen.
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004399:Dynorphins / Q000031:analogs & derivatives / Q000276:immunology / Q000378:metabolism*; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007273:Injections, Intramuscular; D008970:Molecular Weight; D010052:Ovariectomy; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D010446:Peptide Fragments; D004958:Estradiol; D004399:Dynorphins; C026770:dynorphin (1-8); C045485:dynorphin (1-32)