Myatt et al. comparing the presence and localization of eNOS and nitrotyrosine (a marker of peroxynitrite formed by interaction of NO and superoxide) in placental villi from normotensive pregnancies and pregnancies complicated by preeclampsia, found that the later displays greater nitrotyrosine immunostaining in vascular endothelium, in the surrounding vascular smooth muscles and in villous stroma[116]. This evidence concerns the gene NOS3 and preeclampsia.