Immunohistochemical localization of nitric oxide synthase in human fetal membranes

Subject. It has been demonstrated that L-arginine-nitric oxide (NO) system is present in the myometrium during pregnancy where it can regulate uterine contractility. Material and method. We have studied by immunohistochemistry the localization of constitutive endothelial nitric oxide synthase (ecNOS) and brain nitric oxide synthase (bNOS) in human fetal membranes in term non laboring women. Results. The amniotic epithelium and the trophoblast of chorion layer stained intensively for bNOS, while for ecNOS the immunoreactivity uas weak and restricted to trophoblast cells. Conclusion. These findings are suggestive for NO production by the fetal membranes in term pregnancy.