Myometrial oxytocin receptor mRNA concentrations at preterm and term delivery - the influence of external oxytocin.

The hormonal system for induction of term and preterm labour is not fully understood. Therefore, we investigated myometrial gene expressions for neurohypophyseal hormones and their receptors, prostaglandin F(2alpha) and ovarian steroid receptors in women delivered by Caesarean section. Myometrial tissue for real time PCR was collected from 39 women delivered at term before and after the onset of labour and preterm. Women delivered electively at term had significantly higher oxytocin receptor mRNA expressions (2.52 +/- 0.37 oxytocin receptor/actin; median +/- SEM) than those delivered with ongoing labour at term (1.01 +/- 0.34; p = 0.015) and those at preterm (1.08 +/- 0.25; p = 0.004). Sub-analyses revealed that the difference at term pregnancies solely was related to patients receiving oxytocin during labour (p = 0.007). These patients had higher oxytocin peptide mRNA levels than those without labour at term (p = 0.009). PGF(2alpha) receptor mRNA concentrations were 27.80 +/- 3.55, 11.46 +/- 2.87 and 19.54 +/- 5.52 PGF receptor/actin, respectively, for the groups. Women without labour at term had higher concentration than those with labour (p = 0.005). Our results suggest that oxytocin, its receptor and the PGF(2alpha) receptor are involved in the regulation of labour through a paracrine mechanism.