Modification of prostaglandin F-2  synthesis and release in the ewe during the initial establishment of pregnancy

Abstract

Pregnant (N = 10) and non-pregnant (N = 10) ewes were bled every 2 h from Days 12 to 17 after oestrus (oestrus = Day 0). Plasma concentrations of progesterone, 15-keto-13,14-dihydro-PGF-2 alpha and 11-ketotetranor-PGF metabolites were determined in all samples. The number of PGF-2 alpha pulses in non-pregnant ewes was 8.2 +/- 0.4 (mean +/- s.e.m.) with an interpulse interval of 10.7 +/- 0.7 h. Two or 3 pulses of low frequency (interpulse interval = 13.4 +/- 1.6 h) occurred in most non-pregnant ewes before the onset of luteolysis; the interpulse interval then decreased to 7.9 +/- 0.4 h for the 6.0 +/- 0.3 pulses temporally associated with luteolysis. In contrast, the number of PGF-2 alpha pulses in pregnant ewes was lower (2.5 +/- 0.7, 0-8) and the interpulse intervals longer (18.9 +/- 6.1 h). Most pulses occurred on Days 14 and 15 in the pregnant and non-pregnant ewes. The mean concentrations of both PGF-2 alpha metabolites in non-pregnant ewes were highest on Day 15 while basal levels of both metabolites remained constant at all times. In pregnant ewes, the mean concentrations of both metabolites were highest on Day 14; basal concentrations of both metabolites were also highest on Day 14. The mean concentrations of 15-keto-13,14-dihydro-PGF-2 alpha were higher in pregnant than in non-pregnant ewes on Days 13 and 14 (P less than 0.05) and higher in non-pregnant than pregnant ewes on Day 15 (P less than 0.05). The basal concentrations of the 15-keto metabolite were higher in pregnant than non-pregnant ewes at Days 13, 14, 15, 16 and 17 (P less than 0.05). Both the mean and the basal concentrations of 11-ketotetranor-PGF metabolites were higher in pregnant than in non-pregnant ewes on Day 14 (P less than 0.05). It is concluded that uterine production of PGF-2 alpha peaks at Days 14-15 after oestrus in pregnant and non-pregnant ewes. Patterns of release differ, however, in that non-pregnant ewes have a pulsatile PGF-2 alpha pattern superimposed on a constant baseline, while pregnant ewes have an increasing basal secretory pattern which is more nearly continuous, i.e. not pulsatile in form. Modification of pulsatile PGF-2 alpha synthesis and release is therefore a key aspect of prolongation of luteal function at the beginning of pregnancy in the ewe.

BVDV alters uterine prostaglandin production during pregnancy recognition in cows

“…In ruminants, although IFNT inhibits the pulsatile release of PGF 2α by the uterine epithelium, the basal release of PGE 2 and PGF 2α from both the conceptus and the endometrium increases during early pregnancy (Zarco et al 1988. PGs secreted by both epithelial and stromal cells co-ordinate with the IFNT to regulate uterine endometrial functions.…”

“…During PR, IFNT inhibits the up-regulation of oxytocin (OXT) receptors (OXTR) in the uterine epithelium, thereby preventing the pulsatile release of PGF 2α , which is necessary for luteolysis (Wathes & Lamming 1995, Mann et al 1999. In contrast, basal release of PGs, such as PGE 2 and PGF 2α , from both the conceptus and the maternal uterine endometrium rises during early pregnancy (Zarco et al 1988. This increased PG production may facilitate the effects of IFNT on the expression of endometrial type I IFN-stimulated genes (ISGs), a vital component of PR .…”

Quantitative characterization of prostaglandins in the uterus of early pregnant cattle

“…The lack of pulsatile luteolytic PGF 2a during pregnancy is accompanied by a steady-state low level of PGE 2 in the bovine caudal vena cava (Schallenberger et al 1989), although the rise of basal levels and occasional pulses in PGF 2a have been reported in sheep (Zarco et al 1988). The general PG synthase PTGS2 is not inhibited due to the presence of an embryo, instead there is an inconsistent evidence of the effect of IFNT on the expression of the general PG synthase PTGS2, showing either stimulative or no effects , Arosh et al 2004b, Emond et al 2004.…”

Função do interferon-tau durante o reconhecimento materno da gestação em ruminantes

“…Já no bovino, a (FARIN et al, 1990;ROBERTS, 1991;ROBERTS et al, 1991). Como resposta, o IFNT inibe a transcrição de receptores de estrógenos (ESR1; SPENCER & BAZER, 1996) e ocitocina (OXTR; SPENCER & BAZER, 1996;CHEN et al, 2006) no endométrio inibindo a luteólise (ZARCO et al, 1988a;ZARCO et al, 1988b). Na ovelha, esse momento corresponde à elongação do blastocisto que passa de uma forma esférica para filamentosa entre os dias 10 e 17 da gestação (SPENCER et al, 2004) Receptores de interferon tipo I e genes estimulados por interferons (ISGs) Os receptores de interferon tipo I (IFNAR1 e IFNAR2) são expressos em todos os tecidos corporais e têm como função principal mediar respostas antivirais.…”