Influence of embryos on PGF(2 alpha) production by uterine tissue in pregnant mice

The aims of the present study are to find out if preimplantation mice embryos can synthesize prostaglandins and if the presence of the embryos in the uteri modifies the uterine prostaglandin synthesis. Both uteri of adult pregnant mice and embryos were collected at day two, three and four of pregnancy and the synthesis and release of PGE and PGF(2 alpha) was measured by radioimmunoassay. At day five of pregnancy, embryos are tightly adherent to epithelium, so tied uterine horns (without embryos) were compared to control uteri (with embryos). We found that embryos synthesize PGE and PGF(2 alpha) and that PGE is significantly greater on the fourth day of pregnancy than on the second and third day (P < 0.001). In the uteri, during the four days of pregnancy, there is a significant increase in PGE (P < 0.05) and a significant decrease in PGF(2 alpha) (P < 0.01). On the fifth day, the synthesis of PGF(2 alpha) was significantly greater in tied uteri than in controls (P < 0.05). We conclude that mice embryos can synthesize prostaglandins and their presence in uteri significantly decreased the synthesis of PGF(2 alpha) during the peri-implantation period without modifying the production of PGE.