title: Necessity of sequential pulses of prostaglandin F2alpha for complete physiologic luteolysis in cattle.
abstract: The luteolytic effects of exogenous prostaglandin F2alpha (PGF) that did and did not simulate natural 13,14-dihydro-15-keto-PGF (PGFM) pulses were studied during mid-diestrus in 42 Holstein heifers. Plasma concentrations of PGF were assessed by assay of PGFM. In experiment 1, a single intrauterine injection of 4.0 mg of PGF into the uterine horn ipsilateral to the corpus luteum resulted in a precipitous progesterone decline, whereas sequential injections of 0.25 or 1.0 mg every 12 h resulted in a stepwise decrease (P < 0.05) following each injection. A progesterone increase occurred during the first 5 min before the luteolytic decrease but only for the 4.0-mg dose. From the results of experiment 2, a 2-h intrauterine infusion of a total of 0.5 mg of PGF was judged to best simulate a natural PGFM pulse. In experiment 3, simulation of sequential pulses at 12-h intervals resulted in a continuous precipitous decrease in progesterone to <1 ng/ml by the beginning of the fourth simulated pulse. In contrast, a single simulated pulse resulted in a 6-h progesterone decrease to a constant concentration for 3 days after treatment, followed by a return to control concentrations. The mean +/- SEM interval between the pretreatment and posttreatment ovulations was shorter (P < 0.05) in the group with sequential simulated pulses (14 +/- 1 day) than in the group with a single pulse (21 +/- 1 day). Results indicated that excessive PGF doses may stimulate nonphysiologic progesterone responses and supported the hypothesis that sequential PGF pulses are required to stimulate natural luteolysis in cattle.
authors.affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, [corrected] USA. ginther@svm.vetmed.wisc.edu [corrected]
authors.forename: O J
authors.initials: OJ
authors.lastname: Ginther
authors.forename: R R
authors.initials: RR
authors.lastname: Araujo
authors.forename: M P
authors.initials: MP
authors.lastname: Palhão
authors.forename: B L
authors.initials: BL
authors.lastname: Rodrigues
authors.forename: M A
authors.initials: MA
authors.lastname: Beg
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule / Q000662:veterinary; D005260:Female; D003341:Luteolysis / Q000097:blood / Q000187:drug effects* / Q000502:physiology; D011374:Progesterone / Q000097:blood; D011673:Pulsatile Flow / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D016896:Treatment Outcome; D014463:Ultrasonography; D014599:Uterus / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
chemical_list: C008228:15-keto-13,14-dihydroprostaglandin F2alpha; D011374:Progesterone; D015237:Dinoprost