M. Hasegawa et al., ENDOTHELIN-1-LIKE IMMUNOREACTIVITY AND ENDOTHELIN RECEPTORS IN THE HUMAN PLACENTA FROM NORMOTENSIVE AND HYPERTENSIVE PREGNANCIES, Journal of perinatal medicine, 24(5), 1996, pp. 451-460
The levels of endothelin-1-like immunoreactivity (ET-1-LI) and charact
eristics of endothelin receptors in the chorionic villous tissue of hu
man placenta were determined. The ET-1-LI level in chorionic villous t
issue obtained from normal term placenta was 2,450 +/- 940 pg/g wet we
ight (mean +/- SD, n = 4). Further analysis using gel permeation chrom
atography and reverse-phase high performance liquid chromatography sho
wed that the main ET-1-LI constituent of ET-1-LI in this tissue was ET
-1. Scatchard analysis of [I-125]ET-1 binding to the membrane fraction
of chorionic villous tissue obtained from term placenta showed high a
ffinity receptor sites with an apparent dissociation constant (Kd) of
23.6 +/- 11.1 pM and a Bmax value of 388 +/- 238 fmol/mg protein (n =
5). The same binding study with [I-125]ET-3 showed a Kd of 13.9 +/- 3.
8 pM and a Bmax value of 176 +/- 78 fmol/mg protein (n = 5). These res
ults suggest that both ET-A and ET-B receptors (ET-AR and ET-BR) are e
xpressed in chorionic villous tissue. This finding was further confirm
ed by Northern blot analysis showing the expression of both ET-AR and
ET-BR mRNAs in this tissue. ET-1-LI in the umbilical venous plasma of
the newborns from women with pregnancy-induced hypertension (PIH) (38.
3 +/- 10.4 pg/mL, n = 5) was significantly (P < 0.05) higher than that
in the normal newborns from normotensive pregnant women (26.3 +/- 5.2
pg/mL, n = 12). However, in placental chorionic villous tissue obtain
ed from PIH women, both ET-1-LI level and ET binding profile were not
different from those in chorionic villous tissue from normotensive pre
gnant women. These results suggest that the abundant ET-ET receptor sy
stem is present in the placental chorionic villous tissue and that thi
s system is not the major factor of the pathogenesis of placental dysf
unction occurring in PIH because these systems are similar in normoten
sive and hypertensive pregnancies.