Immunocytochemical localization of endothelin-1 in human placenta from normal and preeclamptic pregnancies

Objective, The aim of this study was to examine the distribution of endothelin-1 (ET-1) in the human placenta at different gestational ages and to determine whether differences in ET-1 immunoreactivity occurred in preeclamptic compared with uncomplicated pregnancies. Methods. Localization of ET-1 was investigated by the immunoperoxidase technique in first-trimester, second-trimester, and term human placentas from normal pregnancies and in placentas from preeclamptic pregnancies. Results. In normal placentas from all gestational ages studied, endothelin-l immunoreactivity (ET-1 IR) was specifically detected in the endothelium of the fetal vessels and in the syncytiotrophoblast. ET-I IR was also expressed by the villous cytotrophoblast of first- and second-trimester normal placentas. The extravillous cytotrophoblast of the basal and chorionic plates also exhibited ET-1 IR, but with varying degrees of intensity. In preeclamptic placentas, the expression of ET-1 IR was uneven with a negative staining in all placentas from pregnancies between the 29th and 32nd weeks of gestation. The expression of ET-1 IR was most intense in some syncytiotrophoblast tissue in the terminal villi after the 33rd week of gestation. In placentas from preeclamptic pregnancies between the 35th and the 36th weeks of gestation, strong ET-1 IR expression was evident in the endothelium of fetal vessels and in the syncytiotrophoblast. Regardless of gestational age, ET-1 IR was also observed in the extravillous cytotrophoblast of the basal and chorionic plates of preeclamptic placentas. Conclusion. This study demonstrates that ET-1 IR is widely distributed in the human placenta and provides further evidence to support the concept that ET-1 plays an important role as a modulator of vascular tone in the uteroplacental and fetoplacental units and may participate in the pathogenesis of preeclampsia.