Increased maternal plasma concentration of endothelin-1 during labor pain or on delivery and the existence of a large amount of endothelin-1 in amniotic fluid

Abstract

The concentration of endothelin-1 (ET-1) in plasma and amniotic fluid from normal pregnant women was determined by a sensitive sandwich-enzyme immunoassay system, established recently. The plasma ET-1 level increased gradually during normal pregnancy as the pregnancy advanced, the levels (0.40 ± 0.02 pmol/1, n = 45) being significantly (p < 0.05) higher after 29 weeks of gestation than those (0.32 ± 0.01 pmol/1, n = 30) before 28 weeks of gestation. The plasma ET-1 level during labor pain was significantly higher (0.59 ± 0.06 pmol/1, n = 10) than that (0.40 ± 0.02 pmol/1, n = 45) in the 3rd trimester of pregnancy without labor pain (p < 0.02). Moreover, a high level of ET-1 (17.38 ± 0.25 pmol/1, n = 18) was detected in amniotic fluid on term delivery. The ET-1 level in amniotic fluid was significantly higher than the levels in maternal and umbilical cord plasma (p < 0.001 and p < 0.001, respectively). After delivery the maternal ET-1 level decreased gradually and 2 day postpartum ET-1 levels reached the normal non-pregnant level. Taken together, these results suggest that ET-1 might play an important role in uterine contraction and also participate in labor.