ABSTRACT
The plasma and amniotic fluid concentrations of endothelin-1 (ET-1) and prostaglandin E2 (PGE2) were measured by radioimmunoassay in 81 women, including 20 in the second stage of labor, 14 in the latent period, 15 in the third trimester of pregnancy, 10 in midtrimester, and 12 postpartum women ,and 10 normal nonpregnant women served as control. The results showed that the plasma ET-1 concentrations of women in second stage of labor, latent period, normal third trimester, and midtrimester of pregnancy were significantly higher than those of the normal nonpregnant and postpartum women and increased with pregnancy and labor, with a peak level in second stage of labor. At 24 hours postpartum, the plasma ET-1 concentrations decreased abruptly to the nonpregnant levels. The ET-1 and PGE2 concentrations in amniotic fluid were significantly higher than those in plasma, both at various stages of pregnancy and during labor. The PGE2 levels in plasma and amniotic fluid varied with the ET-1 levels and there was a significant positive correlation at various stages of pregnancy and during labor. The results suggest that ET-1 concentrations in plasma and amniotic fluid increases with gestational length, and produces contractions of pregnant my-ometrium at term. The ET-1 stimulats the production of PGE2 and plays an important role in the initiation and maintenance of labor.