Secretory and cytosolic phospholipase A2 activities and expression are regulated by oxytocin and estradiol during labor

• Published in: Reproduction (Cambridge, England) Vol. 134; no. 2; pp. 355 - 364
• Main Authors: Farina, Mariana Gabriela, Billi, Silvia, Leguizamón, Gustavo, Weissmann, Carina, Guadagnoli, Tamara, Ribeiro, Maria Laura, Franchi, Ana Maria
• Format: Journal Article
• Language: English
• Published: England Society for Reproduction and Fertility 01-08-2007; BioScientifica Ltd
• Subjects: Animals; Cytosol - enzymology; Dinoprost - biosynthesis; Dinoprost - metabolism; Estradiol - blood; Estradiol - physiology; Estrogen Antagonists - pharmacology; Female; Gene Expression - drug effects; Isoenzymes - genetics; Isoenzymes - metabolism; Labor, Obstetric - metabolism; Mifepristone - pharmacology; Oxytocin - blood; Oxytocin - physiology; Phospholipases A2 - genetics; Phospholipases A2 - metabolism; Pregnancy; Progesterone - antagonists & inhibitors; Progesterone - metabolism; Rats; Rats, Wistar; Receptors, Oxytocin - antagonists & inhibitors; Reverse Transcriptase Polymerase Chain Reaction; Tamoxifen - pharmacology; Uterus - drug effects; Uterus - enzymology; Vasotocin - analogs & derivatives; Vasotocin - pharmacology
• ISSN: 1470-1626; 1741-7899
• DOI: 10.1530/REP-07-0078

The release of arachidonic acid from membrane glycerophospholipids through the action of phospholipases (PLs) is the first step in the biosynthesis of prostaglandins (PGs). In reproductive tissues, the most important PLs are cytosolic PLA2 (cPLA2) and types IIA and V of the secretory isoform (sPLA2). The aim of this work was to investigate the role of ovarian steroid hormones and oxytocin (OT) in the regulation of rat uterine PLA2 activity and expression during pregnancy and labor. The activity of sPLA2 increased near labor, whereas cPLA2 activity augmented towards the end of gestation. The levels of sPLA2 IIA and cPLA2 mRNA showed an increase before labor (P<0.05, day 21), whereas sPLA2 V mRNA was not regulated during pregnancy. The administration of atosiban (synthetic OT antagonist) together with tamoxifen (antagonist of estrogen receptors) was able to decrease cytosolic and secretory PLA2 activities, diminish the expression of sPLA2 IIA and cPLA2, as well as decrease PGF2α production before the onset of labor (P<0.01). The ovarian steroid did not affect PLA2 during pregnancy. Collectively, these findings indicate that in the rat uterus, both 17β-estradiol and OT could be regulating the activity and the expression of the secretory and the cytosolic isoforms of PLA2, thus controlling PGF2α synthesis prior to the onset of labor.