“…Endothelin (ET) has been shown to be a potent vasoconstrictor of the human isolated foetoplacental cotyledon (Wilkes et al, 1990) and foetoplacental blood vessels (MacLean et al, 1992) and has the potential to influence placental blood flow either directly or in concert with other vasoactive agents including thromboxane A2, prostaglandin F2., prostacyclin, nitric oxide and atrial natriuretic peptide (De Nucci et al, 1988;Hu et al, 1988;Rae et al, 1989;Wilkes et al, 1990;Cameron et al, 1991). Circulating ET levels have been shown to increase during pregnancy and labour (Mastrogiannis et al, 1991); however, conflicting evidence exists concerning the possible role of ET in the pathogenesis of pre-eclampsia. While some reports have indicated a further elevation of plasma ET levels in this condition (Nova et al, 1991;Clark et al, 1992), more recent studies have not found a significant difference in plasma ET levels between pre-eclamptic and normal pregnancies (Benigni et al, 1992) nor any correlation between plasma ET-1 concentration, blood pressure or renal function during toxaemic pregnancy (Otani et al, 1991).…”