Labor-Associated Regulation of Prostaglandin E and F Synthesis and Action in the Ovine Amnion and Cervix

Abstract

Objective: Prostaglandins (PGs) are key regulators of cervical dilatation and membrane breakdown at the onset of labor. PG synthase and receptor expression has been previously documental in uterine tissues; however, mechansms governing the changes occurring in the cervix and amnion are less well established. The aim of the current study was to determine theh level of expression of PG synthetic enzymes and receptors in these tissues in association withh induced labor in sheep.

Methods: Labor was induced in sheep at 135 days of gestation by continuous fetal dexamethasone infusion. Amnion and cervical tissue was obtained before and after labor for measurement of mRNA encoding enzymes (cytosolic phospholipase A₂ [cPLA₂], PGH synthase-2 [PGHS-2], PGF synthase [PGFS], and PGE synthase [PGES]), and receptors (FP and EP1-4) by real-time polymerase chain reaction (PCR).

Results: cPLA₂ expression increased significantly in cervical tissue at labor onset, whereas expression of the other enzymes measured did not change. There was a marked rise in EP3 expression in the cervix, but abundance of this receptor was lower than EP2 and FP expression, which did not change. The amnion exhibited a labor-associated decrease in PGHS-2, PGFS, and EP mRNA expression.

Conclusion: The regulation of PG synthesis and action occurring in the amnion and cervix in association with labor appear to differ markedly between the two tissues, indicating tissue-specific roles for PGs. The data support a role for increased PG synthesis and action in the cervix and suggest a decrease in PG production and action in the amnion, in sharp contrast to the pattern reported in human amnion.

Keywords

Amnion cervix prostaglandin receptors prostaglandin synthases labor

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