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Quantitative characterization of prostaglandins in the uterus of early pregnant cattle

Physiology-Weihenstephan, Technische Universitaet Muenchen, Weihenstephaner Berg 3, 85354 Freising, Germany¹ Institute of Animal Breeding, Bavarian State Institute for Agriculture, Prof.-Duerrwaechter-Platz 1, D-85586 Grub, Germany² Institute of Clinical Pharmacology/ZAFES, Johann Wolfgang Goethe-University Frankfurt, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany

Correspondence should be addressed to S E Ulbrich; Email: ulbrich{at}wzw.tum.de

Prostaglandins (PGs) are important regulators of reproductive processes including early embryonic development. We analyzed the most relevant PG in bovine uteri at different preimplantation pregnancy stages when compared with non-pregnant controls. Additionally, endometrium and trophoblast tissues were examined regarding specific enzymes and receptors involved in PG generation and function. Simmental heifers were artificially inseminated or received seminal plasma only. At days 12, 15, or 18, post-estrus uteri were flushed for PG determination by liquid chromatography–tandem mass spectrometry. Endometrium and trophoblast tissues were sampled for RNA extraction and quantitative real-time PCR analysis. At all days and points of time examined, the concentration of 6-keto PGF₁ (stable metabolite of PGI₂) was predominant followed by PGF₂>PGE₂>PGD₂TXB₂ (stable metabolite of TXA₂). At days 15 and 18, PG increased from overall low levels at day 12, with a much more pronounced increase during pregnancy. The PGF₂/PGE₂ ratio was not influenced by status. The highest PG concentration was measured at day 15 with 6-keto PGF₁ (6.4 ng/ml) followed by PGF₂ (1.1 ng/ml) and PGE₂ (0.3 ng/ml). Minor changes in endometrial PG biosynthesis enzymes occurred due to pregnancy. Trophoblasts revealed high transcript abundance of general and specific PG synthases contributing to uterine PG. As PGI₂ and PGF₂ receptors were abundantly expressed by the trophoblast, abundant amounts of PGI₂ and PGF₂ in the uterine lumen point towards an essential role of PG for the developing embryo. High amounts of PG other than PGE₂ in the preimplantation uterus may be essential rather than detrimental for successful reproduction.