These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A detailed study of hormonal profiles in mares at luteolysis.
    Author: Shand N, Irvine CH, Turner JE, Alexander SL.
    Journal: J Reprod Fertil Suppl; 2000; (56):271-9. PubMed ID: 20681138.
    Abstract:
    Jugular blood samples were collected at 4 h intervals from six mares during an oestrous cycle to study the hormonal events that occur around the time of luteolysis. Blood samples from day 10 (day 0 = ovulation) until day 3 of oestrus were assayed for prostaglandin metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM), oxytocin, prolactin, progesterone and oestrogen conjugates. PGF2alpha (0.5 or 1.5 mg) was administered to six mid-dioestrous mares and the oxytocin and prolactin responses were measured. One to five large (peak > or =2 x nadir) pulses of PGFM, oxytocin and prolactin were detected in mares during the 3 day period starting on day 13 +/- 0.5. The first PGFM pulse was preceded or accompanied by one or more oxytocin pulses and, overall, large PGFM and oxytocin pulses occurred coincidentally (P < 0.001). During the period of oxytocin and PGFM pulses, progesterone concentrations decreased (P < 0.001) from mid-dioestrous to oestrous values. The first large prolactin pulse occurred as progesterone concentrations approached the nadir and preceded an increase in oestrogen conjugate concentrations by 1.9 +/- 0.6 days. Both PGF2alpha doses significantly increased prolactin concentrations, whereas only the larger dose increased oxytocin concentrations. It is concluded that in mares: (i) PGFM and oxytocin secretion patterns are consistent with the ruminant model of the initiation of luteolysis, in which pulsatile secretion of oxytocin from the posterior pituitary triggers episodic release of uterine PGF2alpha; and (ii) the timing of large prolactin pulses in relation to progesterone and oestrogen conjugates changes indicates that prolactin is more likely to have a role in follicular maturation than in luteolysis.
    [Abstract] [Full Text] [Related] [New Search]