ENDOTHELIN-1 LEVELS IN THE MATERNAL-FETAL DYAD

The aim of this study was to determine the distribution of ET-1 levels in the term maternal-fetal dyad. We also compared the levels of ET-1 between umbilical vessels and assessed the effect of labor on the conc entration of ET-1. The ET-1 levels were measured in plasma from 18 ter m maternal-infant pairs. Amniotic fluid ET-1 levels were also measured in 9 of these pregnancies. The ET-1 levels were determined by radioim munoassay (RTA) after extraction of plasma using Sep-Pak C18 cartridge s. There were no significant differences in the ET-1 levels between th e umbilical artery and vein. However, there were significant differenc es in the umbilical artery concentration in women who labored when com pared with those delivered without labor (6.0 +/- 1.1 vs. 2.7 +/- 0.7 pg/ml; t test, p = 0.022). ET-1 levels were lowest in the maternal pla sma (0.9 +/- 0.2 pg/ml) and highest in the amniotic fluid (83 +/- 15 p g/ml). Assuming that elevated plasma ET-1 levels reflect increased bio activity, the higher mean ET-1 levels in the cord vessels and in the a mniotic fluid when compared to maternal levels suggest a role for ET-1 in the regulation of the fetoplacental circulation and in the constri ction of blood vessels in the uterus after parturition. The higher lev els of ET-1 in the umbilical artery of women who underwent labor impli es that ET-1 is released as a result of the stress of labor.