EVIDENCE FOR PROSTAGLANDINS AND LEUKOTRIENES AS MEDIATORS OF PHASE I OF ESTROGEN ACTION IN IMPLANTATION IN THE MOUSE

The inhibition of the cyclooxygenase and/or the lipoxygenase pathways by indomethacin or nordihydroguaiaretic acid during Phase I of estrogen action interfered with estriol-induced initiation of implantation, but not uterine macromolecular uptake and water imbibition. This inhibition of implantation was completely reversed by supplementation with prostaglandin E₂ or leukotriene C₄- These results suggest that estrogen-induced initiation of implantation in a progesterone-primed uterus is mediated via prostaglandins and leukotrienes as components of Phase I of estrogen action.