title: Plasma and ovarian oestradiol and the variability in the LH surge induced in ewes by the ram effect.
abstract: The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable mainly due to whether an LH surge is induced. The aim of this study was to determine the role of oestradiol (E2) in the ram-induced LH surge. In one study, we measured the plasma concentrations of E2 in ewes of different breeds before and after the 'ram effect' and related these patterns to the presence and latency of the LH surge, while another compared ovarian responses with the 'ram effect' following exposure to rams for 2 or 12 h. In all ewes, the concentration of E2 increased 2-4 h after rams were introduced and remained elevated for 14.5 ± 0.86 h. The quantity of E2 secreted before the LH surge varied among breeds as did the mean concentration of E2. The granulosa cells of IF ewes collected after 12 h exposure to rams secreted more E2 and progesterone and had higher levels of StAR than the 2 h group but in MV ewes there was no differences between these groups for any of these parameters. These results demonstrate that the LH surge induced by the rams is a result of increased E2 secretion associated with increased levels of STAR in granulosa cells and that these responses varied among breeds. The results suggest that the variable occurrence of a LH surge and ovulation may be the result of variable ovarian responses to the 'ram effect' and insensitivity of the hypothalamus to the E2-positive feedback signal.
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK claude.fabre@tours.inra.fr.
authors.forename: Claude
authors.initials: C
authors.lastname: Fabre-Nys
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Audrey
authors.initials: A
authors.lastname: Chanvallon
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Debus
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Dominique
authors.initials: D
authors.lastname: François
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bouvier
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Joelle
authors.initials: J
authors.lastname: Dupont
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Lionel
authors.initials: L
authors.lastname: Lardic
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Didier
authors.initials: D
authors.lastname: Lomet
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Christelle
authors.initials: C
authors.lastname: Ramé
authors.affiliation: UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK UMR 7247 Physiologie de la Reproduction et des ComportementsCNRS, Institut Français du Cheval et de l'Équitation, Université de Tours, PRC Centre INRA Val de Loire, 37380 Nouzilly, FranceUMR 868 'Elevage des Ruminants en Régions Chaudes'2 Place Viala, 34060 Montpellier Cedex 1, FranceINRA SAGAChemin de Borde-Rouge Auzeville, BP 52627, 31326 Castanet Tolosan, FranceINRA BourgesDomaine de la Sapinière, 18390 Osmoy, FranceDepartment of Comparative Biological SciencesRoyal Veterinary College, Hawkshead Lane, South Mimms, Hertfordshire AL9 7TA, UK.
authors.forename: Rex J
authors.initials: RJ
authors.lastname: Scaramuzzi
mesh_terms: D000780:Anestrus / Q000187:drug effects*; D000818:Animals; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D004967:Estrogens / Q000097:blood / Q000494:pharmacology; D004971:Estrus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010060:Ovulation / Q000187:drug effects / Q000502:physiology; D011374:Progesterone / Q000378:metabolism; D012636:Secretory Rate / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D012756:Sheep / Q000502:physiology*
chemical_list: D004967:Estrogens; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone