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 was weak and restricted to trophoblast cells. CONCLUSION: These findings are suggestive for NO production by the fetal membranes in term pregnancy.