Changes in the expression of prostaglandin E and F synthases at induced and spontaneous labour onset in the sheep

Abstract

The differential production of prostaglandin (PG) F 2 and PGE 2 within the uterine compartment may play a role in controlling myometrial contraction. We hypothesized that the enzymes downstream of PG endoperoxide synthase-2 (PGHS-2) determine the ratio of PGF 2 and PGE 2 in the utero-ovarian vein plasma and the time of normal and preterm labour onset. The aim of this study was to simultaneously determine the expression of PGF and PGE synthases (PGFS and PGES) in gestational tissues at spontaneous and induced-preterm labour in sheep. Myometrial, endometrial and placental tissue were obtained from ewes in dexamethasone-induced preterm labour, age-matched control ewes, and ewes in spontaneous term labour for analysis of mRNA expression by real-time PCR. PGFS mRNA expression was significantly increased following dexamethasone-induced and spontaneous labour onset in placentome (P,0·01) but was unchanged in the myometrium and endometrium. In contrast, PGES mRNA expression remained unchanged or decreased. PGHS-2 mRNA expression was increased in all tissues examined in both dexamethasone-induced and spontaneous labour (P,0·001). Plasma PGE 2 and PGF 2 concentrations rose in both dexamethasoneinduced and spontaneous labour with the ratio of PGF 2 :PGE 2 increased with labour onset (P,0·05). These results are consistent with the hypothesis that the increased expression, of PGFS is responsible for the increased PGF 2 :PGE 2 ratio and this, together with increased PGHS-2 expression, accounts for myometrial activity at labour onset. The findings point to PGFS expression as a key factor in regulating the uterotonic process in the sheep.

Membrane Prostaglandin E Synthase-1: A Novel Therapeutic Target

“…A number of studies of the expression of mPGES-1 in fetal membranes, placenta, and myometrium during pregnancy and labor in humans and other species have been reported (Giannoulias et al, 2002;Martin et al, 2002;Alfaidy et al, 2003;Meadows et al, 2003Meadows et al, , 2004 MPGES-1: A NOVEL THERAPEUTIC TARGET Sun et al, 2003;Palliser et al, 2004). PGE 2 is the major vasodilator eicosanoid of the ductus arteriosus and has been suggested to be of importance for maintenance of a patent ductus arteriosus perinatally.…”

Ablation of connexin43 in uterine smooth muscle cells of the mouse causes delayed parturition

“…The cascade of events precipitating labour remains unclear but it is proposed that the myometrium becomes primed to contract before the initiation of labour. This is caused by activation of a series of genes, that encode a number of contractionassociated proteins (Challis and Lye, 1994), including the oxytocin receptor, the prostaglandin F receptor and the gap junction protein connexin43 (Cx43) (Imamura et al, 2000;Palliser et al, 2004;Lye, 1994).…”

Genes Regulating Maternal Recognition of Pregnancy in Domestic Animals: an Update

“…In corpus luteum, PGFS were localized in the large luteal cells and IFNincreased PGES expression (~2-fold) but not PGFS. Palliser et al (2004) demonstrated that the expression of PGFS increased in the placentome following dexamethasone induced and spontaneous labour onset in the sheep. Mondal (2009) reported that the expression of PGFSL-2 mRNA could not be detected in buffalo uterine endometrium at any stage of estrous cycle.…”