Concentrations of endothelin-1 in maternal and umbilical cord blood at various stages of pregnancy.

To examine the role of endothelin (ET) in the maternal and fetal circulation, the levels of endothelin-1-like immunoreactivity (ET-1-LI) in the plasma of maternal vein (MV), umbilical vein (UV), and umbilical artery (UA) were determined by a sensitive radioimmunoassay (RIA). Levels of ET-1-LI in MV did not show any significant change (9.9±1.5 pg/ml, n=26) throughout normal pregnancy and were similar to those of normal nonpregnant women (10.7±2.5 pg/ml, n=5)