title: Influence of the corpus luteum of pregnancy on ovarian function in postpartum ewes.
abstract: This study was conducted to determine the effects of the corpus luteum (CL) of pregnancy and(or) the previously gravid uterine horn (g-UH) on the incidence and site of ovulation and the duration of luteal function in postpartum (PP) ewes. Ewes were laparotomized at d 60 to 80 of gestation and assigned to one of four groups: 1) single g-UH, CL left intact (SI, n = 35); 2) single g-UH, CL removed (SR, n = 30); 3) twin g-UH, CL on both ovaries left intact (TI, n = 21); and 4) twin g-UH, CL removed from one ovary (TR, n = 32). On d 20 PP, the number of follicles on each ovary was determined at laparoscopy, and ewes received (i.m.) 750 IU of hCG. Ovarian structures were determined at laparoscopy on d 24 PP. Blood samples were collected daily from d 20 to 40 PP and assayed for progesterone. more follicles (P < .05) were observed at laparoscopy on d 20 PP in SI/TI than in SR/TR groups (8.4 vs 6.0, respectively; SE = .4). Overall, 52% of the ewes had visible CL 4 d after hCG, and 73% of the ewes had elevated levels of progesterone by 7 d after hCG. The number of g-UH (S vs T) or status of the CL (I vs R) did not affect these responses. For SR ewes with hCG-induced CL on a single ovary, the incidence of CL formation on the ovary adjacent to g-UH was less (P < .05) than that for SI ewes (0 vs 57, respectively). Removal of the CL from S ewes, but not from T ewes, reduced follicular development and ovulation in response to hCG. Perhaps there is a positive systemic effect of the CL of pregnancy on postpartum ovarian function in ewes.
authors.affiliation: Division of Animal and Veterinary Sciences, West Virginia University, Morgantown 26506-6108.
authors.forename: J A
authors.initials: JA
authors.lastname: Hall
authors.forename: R A
authors.initials: RA
authors.lastname: Dailey
authors.forename: E K
authors.initials: EK
authors.lastname: Inskeep
authors.forename: P E
authors.initials: PE
authors.lastname: Lewis
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006080:Ovarian Follicle / Q000502:physiology; D010053:Ovary / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D012756:Sheep / Q000502:physiology*; D014599:Uterus / Q000502:physiology
chemical_list: D006063:Chorionic Gonadotropin; D011374:Progesterone