Over the last several years, endothelin (ET-1) has emerged as an important
mediator in the pathogenesis of pre-eclampsia and preterm labour, as well a
s in the normal function of gestational tissues. While the distribution of
ET and its binding sites in the human placenta have been well studied, much
less has so far been reported about the distribution of placental ET-1 pro
cessing enzymes. By immunohistochemical analysis and immunofluorescence, en
dothelin-converting enzyme-1 (ECE-1), the enzyme that synthesizes ET-1, is
localized to five distinct cell populations in the human placenta: (1) the
endothelial cells lining the maternal basal plate blood vessels, (2) the in
termediate trophoblasts, (3) the endothelial cells lining the chorionic vil
lous blood vessels, (1) the chorionic villous stromal cells and (5) the cho
rionic villous trophoblasts. The localization of ECE-1 corresponds with the
previously reported distribution of ET-1 in the human placenta and is in a
ccordance with the function of this enzyme in regulating vascular tone thro
ugh synthesis of ET-1. The abundance of ECE-1 in the basal plate is consist
ent with a second possible function of this enzyme in affecting uterine con
tractions. ECE-1 may serve as a target for prognosis and therapy in states
of pathologically altered vascular tone and/or altered myometrial smooth mu
scle tone in gestation. (C) 2000 Harcourt Publishers Ltd.