EXPRESSION OF ENDOTHELIN PRECURSOR GENES IN HUMAN TROPHOBLAST IN CULTURE

We have shown previously the presence of immunoreactive endothelin in cultured trophoblastic cells from human term placenta as well as in th e trophoblast-conditioned medium. To confirm whether or not the differ entiated syncytiotrophoblast is a site for endothelin synthesis, we in vestigated, by reverse transcription and polymerase chain reaction, th e expression of the three preproendothelin genes in 3-day cultured tro phoblast. While no endothelin-2 precursor mRNA was detected, preproend othelin-1 mRNA was found to be expressed by the trophoblast. The endot helin-3 precursor gene was also expressed, but at low level and it was detected only after Southern blotting and oligonucleotide hybridizati on. The ability of trophoblast in culture to express the endothelin pr ecursor genes supports the idea that, in human term placenta, villous syncytiotrophoblast that lines the intervillous space containing mater nal blood acts as an endothelial layer.