Current topic: the role of amniotic endothelin in human pregnancy

Endothelin (ET), a potent vasoconstrictor peptide, was originally isolated from culture medium of porcine aortic endothelial cells. Subsequently, ET was also reported to be produced by non-vascular tissues, and to be involved in various biological phenomena in these tissues. Recently, a high concentration of ET-1-like immunoreactivity (ET-1-LI) was detected in human amniotic fluid. Amnion tissue also contained a large amount of ET-1-LI, and cultured amnion cells secreted large amounts of ET-1-LI. The major component of ET-1-LI in these samples was ET-1. Moreover, the expression of prepro-ET-1 mRNA was detected in both amnion tissue and cultured amnion cells, indicating that ET-1 in the amniotic fluid originated from amnion cells. In addition, specific receptors for ET were detected in myometrium, decidua vera, chorion laeve and placenta, by both ligand binding analysis and Northern blot analysis. These findings suggest that ET-1 secreted from amnion cells plays a physiological role in human pregnancy. In this paper, the regulation of ET-1 production and expression of ET-receptors in avascular human amnion tissue are reviewed. The possible importance of amniotic ET in human pregnancy is also discussed.