IMMUNOHISTOCHEMICAL CHARACTERIZATION OF PLACENTAL NITRIC-OXIDE SYNTHASE EXPRESSION IN PREECLAMPSIA

OBJECTIVE: Our purpose was to compare the expression of endothelial ni tric oxide synthase in the placenta and umbilical cord of preeclamptic placenta with that of the normotensive placenta. STUDY DESIGN: We com pared placental endothelial nitric oxide synthase expression in preecl amptic (n = 3) with that in normal (n = 3) pregnancies. Frozen section s of umbilical cords, chorionic plate vessels, and terminal villi were immunostained with a monoclonal endothelial nitric oxide synthase ant ibody (H32).RESULTS: No difference in endothelial nitric oxide synthas e immunostaining in the endothelium of the umbilical cord artery and v ein, chorionic plate vessels, and stem villous vessels was found betwe en preeclamptic and normotensive pregnancies. In contrast, in the pree clamptic placentas endothelial nitric oxide synthase immunostaining wa s seen in the small terminal villous vessels with underlying smooth mu scle layer. In the syncytiotrophoblast endothelial nitric oxide syntha se immunostaining appeared primarily apical in location and diffuse in distribution in the preeclamptic placentas but primarily basal and pu nctate in the normotensive placentas. CONCLUSIONS: Differences in endo thelial nitric oxide synthase expression in terminal villous vessels a nd in syncytiotrophoblast may be a result of vascular alterations or d amage that take place in the placenta in preeclampsia. These differenc es may alter the regulation of blood flow in the fetal and maternal pl acental vasculatures in preeclampsia.