title: The influence of estradiol-17beta and progesterone on peripheral serum concentrations of luteinizing hormone and follicle stimulating hormone in the ovariectomized ewe.
abstract: Serum gonadotropin concentrations were high and variable and fluctuated episodically in short and long term ovariectomized ewes. Treatment with solid silastic implants releasing progesterone (serum levels 1.81 +/- 0.16 ng/ml) had no consistent effect. Treatment with implants releasing estradiol-17beta significantly depressed mean serum gonadotropin concentrations and peak height to values usually seen in intact ewes. This occurred regardless of implant size and serum estradiol-17beta concentrations (range 11 +/- 0.3 pg/ml to 98 +/- 12.8 pg/ml). Progesterone and estradiol-17beta together significantly depressed the frequency of peaks in LH concentration. Following progesterone removal, 95% of the ewes treated with progesterone and estradiol-17beta implants experienced a transient increase in serum LH concentrations similar to the preovulatory surge in intact ewes. Eighty-four percent of the LH surges were accompanied by a surge in serum FSH concentrations. However, following progesterone removal, 5.1 +/- 2.1 FSH surges were observed over six days. Gonadotropin surges occurred regardless of estradiol-17beta implant size and with or without the influence of supplemental estradiol-17beta.
authors.affiliation: Department of Veterinary Physiological Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, S7N OWO, Canada.
authors.forename: N C
authors.initials: NC
authors.lastname: Rawlings
authors.forename: I A
authors.initials: IA
authors.lastname: Jeffcoate
authors.forename: D L
authors.initials: DL
authors.lastname: Rieger