Endothelins and human placental growth: A review

Abstract

Endothelin-1 (ET-1) is synthesized in avascular human amnion; and, immunoreactive ET-1 is present in amniotic fluid in concentrations 10 to 100 times those in blood. ET-1 acts, most commonly, in a local or paracrine manner; therefore, it is possible that amnion/amniotic fluid ET-1 acts on contiguous tissues, namely chorion laeve or placental surface (chorionic) vessels, or in an autocrine fashion on amnion cells. To address these possibilities, the levels of ETA and ETB receptor mRNAs were evaluated in amnion, chorion laeve, decidua parietalis, placenta, and chorionic vessel tissues. By Northern analysis of total RNA (20 μg), ETA and ETB receptor mRNAs were detected in decidua (n=18), placenta (n=14), and chorionic vessels (n=13). In chorion laeve (n=24), ETB receptor mRNA but not ETA receptor mRNA was detected by Northern analysis of total RNA. Northern analysis of chorion laeve poly(A)+ mRNA (1.5–2.5 μg) revealed ETA receptor mRNA at low levels. Neither ETA nor ETB receptor mRNAs were detected in amnion tissue by Northern analysis of total RNA (n=30; placental and reflected amnion from 15 pregnancies) or by Northern analysis of poly(A)+ mRNA (1.5–2.5 μg). Moreover, there was no demonstrable dose-dependent effect of ET-1 on prostaglandin E2 production or DNA synthesis in amnion epithelial cells in primary culture. The findings of this investigation are indicative that ET-1 in amniotic fluid or secreted from amnion may act in a paracrine fashion on chorion laeve by way of the ETB receptor and on chorionic vessels by way of ETA and ETB receptors.