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 I2, PGI2) and that PGI2 enhances the potentials of live birth of mouse embryos. However, the eicosanoid profile of mouse oviducts remains unknown.
Methods: The metabolites of [14C]arachidonic acid by mouse oviducts were analysed by high-performance liquid chromatography. The expression of cyclooxygenase (COX)-1, COX-2 and PGI2 synthase (PGIS) was analysed by western blot analysis and immunohistochemistry. The PGI2 synthetic capacities and the COX transcripts during the preimplantation period were compared. The effects of COX-2 inhibitor on PGI2 production were ascertained.
Results: Mouse oviducts produced, in order of abundance, PGI2, PGD2 and PGE2. 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 PGI2 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 PGI2 production was markedly reduced by a selective COX-2 inhibitor.
Conclusions: Mouse oviducts synthesized maximal PGI2 during day 2-3 p.c., coinciding with the transformation of 2-cell embryos to morulae. The results suggest that oviduct-derived PGI2 may enhance embryo development in a paracrine fashion.