FETAL ENDOTHELIN LEVELS AND PLACENTAL VASCULAR ENDOTHELIN RECEPTORS IN INTRAUTERINE GROWTH-RETARDATION

Objective: To examine endothelin 1 (ET-1) in normal pregnancies and th ose complicated by severe intrauterine growth retardation (IUGR) with normal or increased fetoplacental vascular resistance as assessed by u mbilical artery Doppler flow velocimetry. Methods: Endothelin 1 concen trations were measured by radioimmunoassay in fetal umbilical arterial and venous and maternal venous plasma, and vascular ET-1 receptors we re quantified by radioligand binding methods in placental primary and secondary stem villous vessels. Results: Fetal and maternal ET-1 conce ntrations were similar in normal pregnancy (10-15 pmol/L) and were not influenced by mode of delivery (vaginal versus cesarean). Fetal level s were identical to control values in the growth-retarded fetuses with normal umbilical artery flow, but were markedly elevated (above 50 pm ol/L) in two cases with increased fetoplacental vascular resistance. T he corresponding maternal levels also appeared elevated, but to a less er extent. Endothelin receptors were identified in placental vascular tissue. No differences in receptor-binding characteristics were observ ed between the groups. Conclusion: The increased fetoplacental vascula r resistance present in a proportion of pregnancies complicated by sev ere IUGR may be associated with elevated fetal plasma ET-1 concentrati ons, but with no apparent change in vascular sensitivity to the peptid e.