ENDOTHELIAL NITRIC-OXIDE SYNTHASE IN PLACENTAL VILLOUS TISSUE FROM NORMAL, PREECLAMPTIC AND INTRAUTERINE GROWTH RESTRICTED PREGNANCIES

Nitric oxide (NO) regulates blood how in the human placenta. Gs increa sed resistance to blood flow is seen in the fetal-placental vasculatur e in pregnancies complicated by pre-eclampsia and/or intrauterine grow th restriction (IUGR), we examined expression of endothelial nitric ox ide synthase (eNOS) in these placentas. Placental villous tissue secti ons were obtained from normotensive control (n = 5), IUGR alone (n = 5 ) or pre eclamptic (with or without IUGR) (n = 9) patients, immunostai ned for eNOS and scored for localization, type (punctate or diffuse) a nd intensity of eNOS staining in syncytiotrophoblast and placental ves sels. The significance of differences was calculated using the Mann-Wh itney U-test. No differences in intensity or type of immunostaining in syncytiotrophoblast were seen, placentas from patients with pre-eclam psia with or without IUGR had a significantly more basal distribution of eNOS in syncytiotrophoblast. eNOS immunostaining was absent in term inal villous capillary and faint in stem villous vessel endothelium of normal placentas, but was intense in the endothelium of both of these types of vessels in the IUGR and pre-eclampsia groups, with significa ntly greater staining seen in stem vessels of patients with IUGR alone . This increased eNOS expression and hence increased NO production in the fetal-placental vasculature may be an adaptive response to the inc reased resistance and poor perfusion in these pathological pregnancies .