Endocrine events associated with endometrial function and conceptus development in cattle

Abstract

Regulation and timing of luteolysis during the bovine oestrous cycle is controlled by the initiation and length of progesterone stimulation. Results have demonstrated that early administration of progesterone shortens the interoestrous interval in the ewe and cow, and removal of progesterone stimulation through a progesterone receptor antagonist delays luteolysis in sheep. Current data suggest that down-regulation of progesterone receptors in the uterine epithelium may initiate events involved in the synthesis and release of prostaglandin F2 alpha (PGF2 alpha) for luteolysis. Progesterone is also involved in the stimulation of the uterine secretions that regulate conceptus growth and the release of the bovine trophoblast protein-1 (bTP-1) necessary for inhibiting endometrial PGF2 alpha release. Conceptus secretion of bTP-1, a Type I trophoblast interferon, increases the concentration of the cellular enzyme 2',5'-oligoadenylate synthetase within the endometrium. The biological role of 2',5'-oligoadenylate synthetase in the establishment of pregnancy is discussed.

Utilização prolongada de dispositivo intravaginal contendo progesterona (CIDR®) para indução de folículos persistentes em receptoras de embrião bovino

“…Uma vez que a P 4 estimula a produção de secreções endometriais necessárias para o desenvolvimento embrionário (GEISERT et al, 1992), além de controlar o desenvolvimento do mecanismo luteolítico (SILVIA et al, 1991), estimulando a produção de interferon-τ pelo concepto (MANN et al, 1999) A taxa de concepção do grupo G4 não diferiu entre os demais grupos, provavelmente devido a alguns animais deste grupo terem apresentado "turn-over" folicular durante o tratamento, em função da possível presença de um CL.…”

Effect of preovulatory follicle maturity on pregnancy establishment in cattle: the role ofoocyte competence and the maternal environment

“…In ruminants, the early conceptus relies on progesterone-stimulated production of growth factors and uterine secretions collectively known as histotroph for nourishment (Geisert et al, 1992;Spencer and Bazer, 2002). Ovarian steroids can have an indirect effect on uterine function through estradiol induction of uterine progesterone receptors (Zelinski et al, 1982;Ing and Tornesi, 1997) and progesterone effects on histotroph production (Garrett et al, 1988).…”

Effect of Buserelin on corpus luteum activity and the fertility of dairy cows

“…25 Το επαρκώς αναπτυγμένο έμβρυο εκκρίνει ικανές ποσότη τες τροφό βλαστική ς ιντερφερόνης (bTP-1), μεταξύ 15ης και 17ης ημέρας p.L, 192627 που αναστέλλουν τη σύνθεση της PGF2a με δυο μηχανισμούς. Συμφωνά με τον πρώτο, η bTP-1 αναστέλλει τη ανάπτυξη των υποδοχέων ωκυτο κίνης, 28 ενώ συμφωνά με το δεύτερο η bTP-1 ρυθμίζει την παρουσία του αναστολέα της ενδομήτριας συνθετά σης της προσταγλανδίνης (EPSI).…”