Effect of stress on tissue and plasma levels of immunoreactive beta-endorphin in ovariectomized rats primed with oestrogen and progesterone.
The aim of this study was to investigate the effect of oestrogen and progesterone on levels of immunoreactive beta-endorphin (Ir-beta-EP) in the hypothalamus, anterior pituitary gland, neurointermediate lobe and plasma under normal conditions and conditions of stress. The injection of oestrogen + progesterone into ovariectomized rats increased Ir-beta-EP levels in extracts of anterior pituitary tissue and in plasma, under both normal and stressed conditions. Exposure to a stress reduced the content of anterior pituitary Ir-beta-EP in ovariectomized rats treated with oestrogen + progesterone and also with sesame oil. Such treatment only resulted in increments in plasma Ir-beta-Ep in oil-treated but not in oestrogen + progesterone-treated ovariectomized rats. It was concluded (1) that oestrogen and progesterone are involved in the regulation of resting levels of anterior pituitary Ir-beta-EP during the rat oestrous cycle, (2) that stress reduces levels of anterior pituitary Ir-beta-EP and (3) that increased levels of plasma oestrogen + progesterone inhibit plasma Ir-beta-EP increments which normally accompany exposure to stress.
D000818:Animals; D002369:Castration; D004723:Endorphins / Q000097:blood / Q000378:metabolism*; D004966:Estrogens, Conjugated (USP) / Q000494:pharmacology*; D005260:Female; D010902:Pituitary Gland / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012715:Sesame Oil / Q000494:pharmacology; D013312:Stress, Physiological; D001615:beta-Endorphin
D004723:Endorphins; D004966:Estrogens, Conjugated (USP); D011374:Progesterone; D001615:beta-Endorphin; D012715:Sesame Oil