Studies on the involvement of prostaglandins in implantation in the rat

Studies of prostaglandin (PG) production by uterine homogenates of rats in early pseudopregnancy and pregnancy showed that production of 6-oxo-PGF-1 alpha, PGF-2 alpha and PGE-2 peaked on Day 5 of pseudopregnancy whereas only 6-oxo-PGF-1 alpha and PGE-2 peaked on Day 5 of pregnancy, the day of implantation. 6-Oxo-PGF-1 alpha was the major product in both reproductive states. Indomethacin treatment of rats during early pregnancy caused a delay in implantation, a significant reduction in uterine weight, and a much reduced number or absence of implanted blastocysts in the uterus on Day 9. Plasma progesterone levels were also significantly lower in indomethacin-treated, pregnant rats. These findings support roles for prostaglandins in implantation, and in fetal development.