Immunohistochemical localization of cyclooxygenase 2 (COX2, PTGS2) and prostaglandin F2 α synthase (PGFS/AKR1C3). Immunohistochemical (IHC) localization of COX2 (PTGS2) at interplacental uterine sites during mid-gestation (A), as well as in the utero-placental compartment (B,C), and interplacental uterine sites (D,E) during Aglepristone® (Agl.)-induced abortion. IHC localization of PGFS/AKR1C3 in the uterus pre-implantation (F), post-implantation (G) and in the utero-placental compartment (H,I) and interplacental uterine sites (J,K) during Aglepristone® (Agl.)-induced abortion. Whereas no or only very weak COX2 IHC signals are observed in uterine endometrium (open arrows = surface luminal epithelium, solid arrowhead = uterine gland), clearly visible staining is localized in myometrium (A). In the utero-placental compartment during Agl.-induced parturition, placental COX2 is localized to the fetal trophoblast cells (solid arrows in B); there are only very weak signals in the uterine glands (solid arrowhead in C), but strong ones are present in myometrium (open arrowhead in C). In the interplacental sites, following Agl. treatment, strong COX2 staining is localized in myometrium (open arrowhead in E), and only very weak staining is present in surface (luminal) uterine epithelium (open arrows in D) and uterine glands (solid arrowheads in D and E). No or only very weak uterine signals are observed for PGFS/AKR1C3 pre-implantation (F). Following implantation, PGFS/AKR1C3 protein is localized in surface (luminal) uterine epithelium and endometrial superficial glands (open and solid arrows in G). In the utero-placental compartment during Agl.-induced parturition, placental PGFS/AKR1C3 protein is localized to the fetal trophoblast cells (solid arrows in H); strong signals are localized also in the superficial endometrial glands, the so-called glandular chambers (open arrows in I). Within the interplacental uterine sites, in Agl.-treated animals, PGFS/AKR1C3 staining is localized predominantly in surface (luminal) uterine epithelium (open arrows in J); the open and solid arrowheads in (K) indicate myometrium and uterine glands, respectively, with barely detectable signals.