Oviduct prostacyclin functions as a paracrine factor to augment the development of embryos

Background: Recently we discovered that human oviducts produce a significant amount of prostacyclin (prostaglandin I-2, PGI(2)) and that PGI(2) enhances the potentials of live birth of mouse embryos. However, the eicosanoid profile of mouse oviducts remains unknown. Methods: The metabolites of [C-14]arachidonic acid by mouse oviducts were analysed by high-performance liquid chromatography. The expression of cyclooxygenase (COX)-1, COX-2 and PGI(2) synthase (PGIS) was analysed by western blot analysis and immunohistochemistry. The PGI(2) synthetic capacities and the COX transcripts during the preimplantation period were compared. The effects of COX-2 inhibitor on PGI(2) production were ascertained. Results: Mouse oviducts produced, in order of abundance, PGI(2), PGD(2) and PGE(2). Western blot analysis confirmed the expression of COX-1, -2 and PGIS which were expressed by luminal epithelia and smooth muscle cells. Day 2-3 post-coitus (p.c.) oviducts produced PGI(2) 10-fold higher than day 4 p.c. oviducts (P=0.0087); day 1 p.c. oviducts expressed COX-2 transcript 5-fold higher than day 3 p.c. oviducts (P=0.0004). The PGI(2) production was markedly reduced by a selective COX-2 inhibitor. Conclusions: Mouse oviducts synthesized maximal PGI(2) during day 2-3 p.c., coinciding with the transformation of 2-cell embryos to morulae. The results suggest that oviduct-derived PGI(2) may enhance embryo development in a paracrine fashion.