title: Follicle deviation and diurnal variation in circulating hormone concentrations in mares.
abstract: The temporal relationships between follicle deviation and systemic hormone concentrations were studied in mares. Blood samples were obtained at 01:00, 07:00, 13:00, and 19:00 h from nine mares throughout an interovulatory interval. Diurnal variation in progesterone occurred on Days 4-12 and in LH on Days 4 and 5; the lowest concentration for both hormones was at 13:00 h. Ultrasonically observed deviation in the ovulatory follicular wave began on Day 15.7+/-0.5 (ovulation=Day 0). An increase (P<0.002) in LH began on Day 14 before the beginning of deviation, and an increase (P<0.05) in estradiol began at the beginning of deviation. Testosterone concentrations began to increase (P<0.05) 2 days after the beginning of deviation and reached maximum 1 day before the next ovulation. The beginning of deviation was encompassed by a decline (P<0.003) in cortisol concentrations, and the concentrations remained low during the preovulatory period.
authors.affiliation: Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu <ginther@svm.vetmed.wisc.edu>
authors.forename: O J
authors.initials: OJ
authors.lastname: Ginther
authors.forename: M D
authors.initials: MD
authors.lastname: Utt
authors.forename: M A
authors.initials: MA
authors.lastname: Beg
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D006736:Horses / Q000097:blood* / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D013739:Testosterone / Q000097:blood; D013997:Time Factors
chemical_list: D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D006854:Hydrocortisone