title: Mechanisms regulating prostaglandin H2 synthase-2 mRNA level in the amnion and chorion during pregnancy.
abstract: Increasing prostaglandin H(2) synthase (PGHS)-2 expression in the fetal membranes is implicated in the production of prostaglandins (PGs) that stimulate labour. We have determined the activity of the PGHS-2 gene in the amnion and chorion throughout gestation and defined the contribution of transcriptional and post-transcriptional mechanisms to the increase of PGHS-2 mRNA levels. We also measured PGHS-1 mRNA abundance to assess the participation of the two isoenzymes in fetal membrane PG-production during pregnancy. Amnion and chorion were collected from non-labouring women at 10-19 weeks (early), at 28-36 weeks (preterm) and at term (37-41 weeks). We determined PGHS-1 and -2 mRNA abundance and assessed PGHS-2 gene activity by measuring PGHS-2 heterogeneous nuclear RNA levels using real-time RT-PCR. PGHS-2 gene activity and mRNA levels were up-regulated in both tissues with advancing gestation. Path analysis demonstrated that the PGHS-2 mRNA up-regulation involved both transcriptional and post-transcriptional components. PGHS-2 mRNA abundance increased 9-11 fold between the early (10-19 weeks) and preterm (28-36 weeks) groups and remained high at term. The underlying mechanism was predominantly transcriptional in the amnion and post-transcriptional in the chorion. PGHS-1 mRNA expression precipitously decreased between early gestation and term. Thus, PGHS-2 mRNA abundance is up-regulated well in advance of term and is not a trigger for labour. There is a switch in PGHS mRNA expression during pregnancy with PGHS-1 dominating in the early period and PGHS-2 dominating at term.
authors.affiliation: Division of Obstetrics and Gynaecology, John Hunter Hospital, Newcastle, New South Wales, Australia.
authors.forename: Renée F
authors.initials: RF
authors.lastname: Johnson
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Mitchell
authors.forename: Warwick B
authors.initials: WB
authors.lastname: Giles
authors.forename: Andrew
authors.initials: A
authors.lastname: Bisits
authors.forename: Tamas
authors.initials: T
authors.lastname: Zakar
mesh_terms: D000650:Amnion / Q000201:enzymology*; D002823:Chorion / Q000201:enzymology*; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D007743:Labor, Obstetric / Q000378:metabolism; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011263:Pregnancy Trimester, Third; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; D051546:Cyclooxygenase 2