title: Cortisol interferes with the estradiol-induced surge of luteinizing hormone in the ewe.
abstract: Two experiments were conducted to test the hypothesis that cortisol interferes with the positive feedback action of estradiol that induces the luteinizing hormone (LH) surge. Ovariectomized sheep were treated sequentially with progesterone and estradiol to create artificial estrous cycles. Cortisol or vehicle (saline) was infused from 2 h before the estradiol stimulus through the time of the anticipated LH surge in the artificial follicular phase of two successive cycles. The plasma cortisol increment produced by infusion was approximately 1.5 times greater than maximal concentrations seen during infusion of endotoxin, which is a model of immune/inflammatory stress. In experiment 1, half of the ewes received vehicle in the first cycle and cortisol in the second; the others were treated in reverse order. All ewes responded with an LH surge. Cortisol delayed the LH surge and reduced its amplitude, but both effects were observed only in the second cycle. Experiment 2 was modified to provide better control for a cycle effect. Four treatment sequences were tested (cycle 1-cycle 2): vehicle-vehicle, cortisol-cortisol, vehicle-cortisol, cortisol-vehicle. Again, cortisol delayed but did not block the LH surge, and this delay occurred in both cycles. Thus, an elevation in plasma cortisol can interfere with the positive feedback action of estradiol by delaying and attenuating the LH surge.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Wagenmaker
authors.forename: Kellie M
authors.initials: KM
authors.lastname: Breen
authors.forename: Amy E
authors.initials: AE
authors.lastname: Oakley
authors.forename: Bree N
authors.initials: BN
authors.lastname: Pierce
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Tilbrook
authors.forename: Anne I
authors.initials: AI
authors.lastname: Turner
authors.forename: Fred J
authors.initials: FJ
authors.lastname: Karsch
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D004731:Endotoxins / Q000009:adverse effects / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000097:blood* / Q000187:drug effects; D025461:Feedback, Physiological / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood* / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood*; D023421:Models, Animal; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology; D012756:Sheep; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D004731:Endotoxins; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D006854:Hydrocortisone