Endothelins-1, 2 and 3 are released in vitro from the human bilaterally perfused placenta

Immunoreactive-endothelin (ir-ET) has previously been detected in human fetal effluents from in vitro perfused placentae. To date however, because of a lack of radio-immunoassay specificity, the ET isoforms in fetal effluents had not been determined, nor had placental maternal effluents been examined for ETs. The aim of this study was to identify the isoforms of ET released into the maternal and fetal circulations of the human in vitro bilaterally perfused placenta. Both circulations of placentae, obtained after normal vaginal delivery, were perfused with a modified Krebs solution and maternal and fetal effluents from the start of the second hour of perfusion were collected, extracted on Scp-pak C18 cartridges, concentrated by vacuum evaporation and separated by reverse-phase HPLC separation. HPLC fractions were measured by ET-RIA and compared to known synthetic standards. Maternal and fetal effluents contained ET-1 (natural and oxidised ET-1), ET-2 and ET-3 (n = 5). Maternal and fetal release of ET-1 was 2.2 +/- 0.7 and 1.4 +/- 0.1 fmol/min/g wet weight of tissue respectively, ET-2 was 0.4 +/- 0.2 and 0.5 +/- 0.2 and fmol/min/g respectively, and ET-3 was 0.5 +/- 0.2 and 0.7 +/- 0.4 fmol/min/g respectively. There were no significant differences between the release of either ET-1, ET-2 or ET-3 in the maternal or fetal circulations. In conclusion, this study indicated that ET-1, ET-2 and ET-3 were all released into both the maternal and fetal effluents from the in vitro perfused human placenta.