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DC Wathes, SC Borwick, PM Timmons, ST Leung and S Thornton

Oxytocin receptor (OTR) mRNA expression has previously been demonstrated in human myometrium, decidua, chorion and amnion but the effect of gestational age and the onset of labour has not been determined in these individual tissues. Spatial OTR mRNA expression was examined by in situ hybridization and ligand binding was confirmed using autoradiography with the iodinated oxytocin antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OTA). Tissue was collected at term (>37 weeks of gestation) or preterm (24-36 weeks of gestation) caesarean section and classified as labour (contractions every 5 min associated with cervical dilatation) or non-labour. OTR mRNA expression was measured as optical density units from autoradiographs. There was a highly significant (P<0.001) effect of tissue type on expression of OTR mRNA with expression greatest in myometrium, low in decidua and chorion and not detected in placenta. Similar results were obtained with the 125I-OTA-binding studies, indicating that the message was translated. Amnion had an apparently high level of both hybridization and 125I-OTA binding in some samples, but a lack of specificity prevented quantification of the signal in this tissue type. Term myometrium (labour and non-labour) had significantly higher (P<0.01) OTR mRNA expression than preterm myometrium, but there was no further increase in mRNA concentration associated with labour onset. In contrast, 125I-OTA binding in myometrium was already high at 33 weeks and did not increase further either later in pregnancy or with labour. In decidua there was no effect of gestational age or labour onset on OTR mRNA expression or 125I-OTA binding. In summary, OTR mRNA expression in the myometrium increased in late pregnancy whereas decidual expression was much lower and did not rise at term.

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ST Leung, Z Cheng, EL Sheldrick, K Derecka, K Derecka, AP Flint and DC Wathes

Up-regulation of endometrial oxytocin receptor (OTR) expression followed by an increase in pulsatile endometrial prostaglandin (PG) F(2alpha) secretion causes luteolysis in cattle. Inhibition of luteolysis is essential for the maternal recognition of pregnancy but also occurs in association with endometritis. The factors regulating OTR expression at this time are unclear. The OTR gene promoter region contains binding elements for acute phase proteins but their function has not been established. This study investigated the effects of various cytokines on OTR expression and on PGF(2alpha) and PGE(2) production in explant cultures of bovine endometrium. Endometrium was collected in the late luteal phase (mean day of cycle 15.4+/-0.50) or early luteolysis (mean day of cycle 16.4+/-0.24) as determined by the initial concentration of endometrial OTR. Explants were treated for 48 h with: (i) lipopolysaccharide (LPS) and/or dexamethasone (DEX), (ii) ovine interferon-tau (oIFN-tau), or (iii) human recombinant interleukin (IL)-1alpha, -2 or -6. OTR mRNA was then measured in the explants by in situ hybridisation and the medium was collected for measurement of PGF(2alpha) and PGE(2) by RIA. LPS treatment stimulated production of PGF(2alpha), whereas DEX either alone or in combination with LPS was inhibitory to both PGF(2alpha) and PGE(2). Neither of these treatments altered OTR mRNA expression. oIFN-tau reduced OTR mRNA expression but stimulated production of both PGF(2alpha) and PGE(2). In endometrial samples collected in the late luteal phase, IL-1alpha, -2 and -6 all inhibited OTR mRNA expression, but IL-1alpha and -2 both stimulated PGF(2alpha) production. In contrast, when endometrium was collected in early luteolysis, none of the interleukins altered OTR expression or caused a significant stimulation of PGF(2alpha) production but IL-2 increased PGE(2). Neither IL-1alpha nor -2 altered OTR promoter activity in Chinese hamster ovary cells transfected with a bovine OTR promoter/chloramphenicol acetyl transferase reporter gene construct. In conclusion, the action of interleukins on both OTR mRNA expression and endometrial prostaglandin production alters around luteolysis. Pro-inflammatory interleukins suppress OTR expression in the late luteal phase, while LPS stimulates PGF(2alpha) without altering OTR mRNA expression. IL-I and -2 and LPS are therefore unlikely to initiate luteolysis but may cause raised production of PGF(2alpha) during uterine infection.

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C Barberis, B Mouillac and T Durroux

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Lucia Gajdosechova, Katarina Krskova, Ana Belen Segarra, Andrea Spolcova, Maciej Suski, Rafal Olszanecki and Stefan Zorad

et al . 2011 , Morton et al . 2012 , Zhang et al . 2013 ). In vivo physiological levels of circulating oxytocin depend on its synthesis, receptor-mediated internalisation and degradation by oxytocinase. Oxytocinase (cystinyl aminopeptidase, EC 3

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S Babic, M Pokusa, V Danevova, S T Ding and D Jezova

Introduction Atosiban is a known antagonist of oxytocin and vasopressin receptors and is clinically used to decrease preterm uterine activity and preterm labor ( Goodwin et al . 1994 , Usta et al . 2011 ). Generally, atosiban is considered to be

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A Levoye, B Mouillac, G Rivière, D Vieau, M Salzet and C Breton

Introduction The arginine-vasopressin (AVP)/oxytocin (OT) neuro-endocrine system is widely distributed in the animal kingdom. In vertebrates, more than 10 related peptides and over 30 related receptors belonging to the G

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E Houdeau, A Lévy and S Mhaouty-Kodja

role in the regulation of uterine contractility. Indeed, contractant factors like oxytocin (OT), prostaglandins or norepinephrine utilize PLC-coupled receptors (OT receptors (OTR), prostaglandin F2α receptors (FP) and α1-adrenergic receptors (AR

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Georgina G J Hazell, Song T Yao, James A Roper, Eric R Prossnitz, Anne-Marie O'Carroll and Stephen J Lolait

protein-coupled receptor from rat lung . Biochemical and Biophysical Research Communications 8 190 – 193 . Bossmar T Forsling M Akerlund M 1995 Circulating oxytocin and vasopressin is influenced by ovarian steroid replacement in women

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M Jankowski, D Wang, S Mukaddam-Daher and J Gutkowska

investigate the expression of natriuretic peptides, NOS and cGMP in the rat LV throughout gestation and early postpartum. Because of their contribution to ANP and NO release in the cardiovascular system, estrogen and oxytocin receptors (OTR) were also

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Toni Welsh, Matrika Johnson, Lijuan Yi, Huiqing Tan, Roksana Rahman, Amy Merlino, Tamas Zakar and Sam Mesiano

1993 , Kilarski et al . 1996 , 2000 ), receptors for uterotonic hormones such as oxytocin and prostaglandin F 2 α (PGF 2 α ; Pinto et al . 1966 , 1967 , Nissenson et al . 1978 ), and enzymes such as PG-endoperoxide synthase-2 (PTGS2), the main