[Levels of endothelin-1 in maternal and cord plasma during pregnancy and delivery].
In order to elucidate the possible involvement of endothelin-1 (ET-1) in the development of the feto-placental unit, plasma concentrations of immunoreactive ET-1 during pregnancy and delivery were measured in the current study. Forty-four pregnant women (8 in the 1st trimester, 8 in the 2nd trimester, 12 in the 3rd trimester and 16 at delivery), 6 at 1 month postpartum and 14 non-pregnant women volunteered to participate in this study. Plasma levels of immunoreactive ET-1 in all subjects were measured by specific radioimmunoassay. Plasma cortisol, prolactin and oxytocin levels during delivery were also measured by RIA. Although plasma ET-1 levels did not change during the 1st (1.3 +/- 0.4 pg/ml, mean +/- S.E.M., n = 8) or 2nd (1.7 +/- 0.3 pg/ml, n = 8) trimester, they were significantly (p less than 0.05) higher in the 3rd trimester (2.6 +/- 0.3 pg/ml, n = 12) than those of the non-pregnant controls (1.7 +/- 0.3 pg/ml, n = 14) and returned to the control levels within 1 month post-partum (1.8 +/- 0.1 pg/ml, n = 6). Maternal ET-1 levels before labor onset (2.3 +/- 0.4 pg/ml, n = 16), at delivery (3.0 +/- 0.7 pg/ml) and 24 hours post-partum (2.7 +/- 0.5 pg/ml) showed no significant differences among them. On the other hand, ET-1 levels in cord plasma (7.0 +/- 1.2 pg/ml) were significantly higher (p less than 0.05) than those in maternal plasma. Furthermore, there were no significant correlations between plasma ET-1 levels and those of other hormones (cortisol, prolactin and oxytocin) during delivery. From these results, we concluded that maternal plasma ET-1 levels significantly increased in the last trimester and returned to non-pregnant levels within one month post-partum.