The effect of prostaglandins F₂α and E₂ on pregnancy in mice during implantation

The uterine content of prostaglandins (PGs) increases following insertion of an intrauterine device (IUD). Such IUD-bearing uteri also exhibit impaired decidualization. Although prostaglandins have been shown to be luteolytic in several species, it is not clear that inhibition of decidualization is mediated solely through alterations in ovarian steroidogenesis. In these experiments, ovariectomized, hormone-replaced pregnant mice, as well as intact mice, were treated systemically with either PGE₂ or PGF₂α so that the extraovarian actions of prostaglandins upon decidualization could be segregated from effects mediated by alterations in ovarian steroidogenesis. The results suggest that the effect of PGF₂α upon decidualization was mediated via an alteration in ovarian steroidogenesis, but that PGE₂ acted independently of the ovary. The hypothesis is presented that alterations in the ratio of E to F prostaglandins elicited within the endometrium by an IUD inhibit decidualization at the uterine level, and that this effect might be mediated by impairment of histamine release from endometrial mast cells.