ENDOTHELIN-1 RECEPTORS ON THE HUMAN PLACENTA AND FETAL MEMBRANES - EVIDENCE FOR DIFFERENT BINDING-PROPERTIES IN PREECLAMPTIC PREGNANCIES

Densities and affinities of tissue protein receptor sites for endothel in-1 in placental and fetal membranes of six pre-eclamptic and 16 norm otensive women in the 36-41th week of gestation were determined by the use of a binding assay with [I-125]endothelin-1. The mean maximal den sity of receptor sites (B(max)) was significantly higher in the placen tas of the pre-eclamptic than of the normotensive women (905 +/- 107 v s. 539 +/- 140 fmol/mg protein, p < 0.0001). No differences uere found between the two groups with respect to the mean affinity (K(d)) of pl acental receptors, or the mean B(max) and the mean K(d) of fetal chori onic samples. In the normotensive group, there uere no differences in mean placental B(max) values or in mean K(d) values between women who went into spontaneous labor (whether delivered vaginally or abdominall y) and those who uere electively operated on prior to labor onset. No binding sites uere detected in the fetal amniotic membranes of any of the women. Our results suggest that an increase in the maximal density of receptor sites to endothelin-1 in the placenta may play a role in the pathophysiology of pre-eclampsia by contributing to the placental insufficiency that characterizes this disorder.