The effect of chronic estrogen treatment on immunoreactive beta-endorphin levels in intact female rats.
Intact female rats were treated chronically with estradiol benzoate (EB) until a state of constant estrus (CE) was achieved and maintained. When compared to female rats on the day of estrus, estrogen-treated rats in constant estrus demonstrated a 33% decrease in the concentration of immunoreactive beta-endorphin (IR-BE) in the plasma, and a 45-50% decrease in the content and concentration of IR-BE in the anterior pituitary and hypothalamus. The content and concentration of IR-BE in the neurointermediate lobe of the pituitary were similar in each group. Column chromatography revealed that the reduction in IR-BE in the plasma and anterior pituitary of EB-treated CE female rats appeared to be due to a reduction in peptides coeluting with beta-endorphin and beta-lipotropin, whereas the reduction in IR-BE in the hypothalamus represented a decrease in a peptide which coeluted with beta-endorphin. These data suggest that constant estrus, induced by prolonged treatment of intact female rats with estrogen, resulted in a reduction in central and peripheral levels of IR-BE in these animals as compared to female rats on the day of estrus.
Forman
L J
LJ
Marquis
D E
DE
Stevens
R
R
D000818:Animals; D002850:Chromatography, Gel; D004723:Endorphins / Q000276:immunology / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D009929:Organ Size; D010053:Ovary / Q000033:anatomy & histology; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011247:Pregnancy; D011863:Radioimmunoassay; D051381:Rats; D014599:Uterus / Q000033:anatomy & histology; D001615:beta-Endorphin
D004723:Endorphins; D004958:Estradiol; D001615:beta-Endorphin