title: Effects of ovariectomy, gonadal steroid replacement and photoperiod on plasma beta-endorphin in the ewe.
abstract: The effects of gonadectomy, photoperiod and ovarian steroid replacement on plasma beta-endorphin concentrations were studied in 2 experiments using mature ewes. In Experiment 1 ovariectomy resulted in an increased plasma beta-endorphin concentration. Changing the photoperiod from long to short daylength had little effect on beta-endorphin, but transfer from short to long photoperiod caused a fall in the beta-endorphin level. In Experiment 2 ovariectomy again caused an increase in plasma beta-endorphin. Treatment with progesterone, estradiol or a combination of both failed to reduce the level to preovariectomy values, although LH concentrations were reduced. No diurnal rhythmicity in beta-endorphin secretion was observed.
authors.affiliation: Department of Animal Physiology and Nutrition University of Leeds, Leeds LS2 9JT, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Durotoye
authors.forename: S
authors.initials: S
authors.lastname: Al-Gahtani
authors.forename: D P
authors.initials: DP
authors.lastname: Fordham
authors.forename: R G
authors.initials: RG
authors.lastname: Rodway