To examine endothelin 1 (ET-1) in normal pregnancies and those complicated by severe intrauterine growth retardation (IUGR) with normal or increased fetoplacental vascular resistance as assessed by umbilical artery Doppler flow velocimetry.Methods:
Endothelin 1 concentrations were measured by radioimmunoassay in fetal umbilical arterial and venous and maternal venous plasma, and vascular ET-1 receptors were quantified by radioligand binding methods in placental primary and secondary stem villous vessels.Results:
Fetal and maternal ET-1 concentrations were similar in normal pregnancy (10-15 pmoI/L) and were not influenced by mode of delivery (vaginal versus cesarean). Fetal levels were identical to control values in the growthretarded fetuses with normal umbilical artery flow, but were markedly elevated (above 50 pmol/L) in two cases with increased fetoplacental vascular resistance. The corresponding maternal levels also appeared elevated, but to a lesser extent. Endothelin receptors were identified in placental vascular tissue. No differences in receptor-binding characteristics were observed between the groups.Conclusion:
The increased fetoplacental vascular resistance present in a proportion of pregnancies complicated by severe IUGR may be associated with elevated fetal plasma ET-1 concentrations, but with no apparent change in vascular sensitivity to the peptide.