Oxytocin (OXT) and tumor necrosis factor α (TNF) have been implicated in the control of luteolysis by stimulating endometrial secretion of luteolytic prostaglandin F2α(PGF2α). Nevertheless, OXT concentration in porcine uterine lumen increases markedly on days 11–12 of pregnancy, and TNF is expressed in endometrium during pregnancy. The objective of the study was to determine the effect of OXT and TNF on expression of the enzymes involved in PG synthesis: PG-endoperoxide synthase 2 (PTGS2), PGE2synthase (mPGES-1) and PGF synthase, and PGE2receptor (PTGER2), as well as on PG secretion by endometrial luminal epithelial cells (LECs) on days 11–12 of the estrous cycle and pregnancy. LECs isolated from gilts on days 11–12 of the estrous cycle (n=8) and pregnancy (n=7) were treated with OXT (100 nmol/l) and TNF (0.6 nmol/l) for 24 h. OXT increasedPTGS2mRNA and mPGES-1 protein contents, as well as PGE2secretion but only on days 11–12 of pregnancy. TNF stimulatedPTGS2andmPGES-1mRNA, as well as mPGES-1 protein expression and PGE2release on days 11–12 of pregnancy and the estrous cycle. In addition, expressions of PTGER2 and PTGER4 were determined in corpus luteum (CL). Abundance ofPTGER2mRNA and PTGER4 protein in CL was upregulated on day 14 of pregnancy versus day 14 of the estrous cycle. This study indicates that TNF and OXT regulate PGE2synthesis in LECs during early pregnancy. PGE2secreted by LECs, after reaching ovaries, could have a luteoprotective effect through luteal PTGER2 and PTGER4, or may directly promote uterine function and conceptus development.
Molecular Cloning and Characterization of Bovine Prostaglandin E2 Receptors EP2 and EP4: Expression and Regulation in Endometrium and Myometrium during the Estrous Cycle and Early Pregnancy