Prostaglandins and ovum implantation in mice.

The possible involvement of prostaglandins (PGs) in events of ovum implantation is investigated. The levels of PGF and PGE-A were measured by radioimmunoassay in the implantation and interimplantation sites on days 4, 5, 6, and 7 of pregnancy. The concentration of prostaglandins was determined in morulae and blastocysts also. The levels of PGE-A were higher in implantation sites in comparison to PGF. PGE-A level showed a peak on d5 and remained significantly higher on d6 and d7, in comparison to d4. The concentration of PGF was found to be very low in both interimplantation sites and implantation sites before implantation. The concentration of PGF showed a significant increase on d6 in the interimplantation sites which peaked up to 32.61 +/- 2.01 ng on d7. The embryos showed an increase in PGE-A concentration along with development. However, PGF could not be found in the embryos. The present result shows that in mice PGE is the main prostaglandin involved in ovum implantation and PGF is associated with maintaining the embryos in the uterus. It is also predicted that in mice, blastocysts differentially stimulate PG synthesis in the uterus between implantation sites and interimplantation sites.