Ch. Blomquist et Pt. Dascoli, GESTATIONAL DEVELOPMENT OF HUMAN PLACENTAL 17-BETA-HYDROXYSTEROID OXIDOREDUCTASE TYPE-1 AND TYPE-2, Human reproduction, 10(10), 1995, pp. 2685-2689
Human placenta is a rich source of 17 beta-hydroxysteroid oxidoreducta
se (17-HOR) type 1, a cytosolic enzyme highly specific for 17 beta-oes
tradiol, and type 2, a microsomal form reactive with both oestradiol a
nd testosterone. Although a number of studies have established that 17
-HOR activity is present in placenta as early as weeks 4-5 of gestatio
n, more specific data on the pattern of development of these two enzym
e forms are lacking, In this study, samples of villous tissue from wee
ks 7-20 of gestation were fractionated into cytosol and microsomes and
17-HOR activity assayed under conditions which differentiate between
the two enzyme types. Type 1 activity with oestradiol of cytosol and m
icrosomal type 2 activity with oestradiol and testosterone increased f
rom week 7 to week 20. Activities at 17-20 weeks approximated those at
38-40 weeks, The high, cytosolic oestradiol/T activity ratio (160 +/-
20), characteristic of 17-HOR type 1, was constant between weeks 7 an
d 20, as was the low microsomal ratio (3.4 +/- 0.4) characteristic of
the type 2 activity, There was a relationship between cytosolic type 1
activity and microsomal type 2 activity between weeks 7 and 20 (r = 0
.59, P = 0.0055), These results indicate both activities increase coin
cident with the luteal-placental shift and that their temporal pattern
s of development are related between weeks 7 and 20 of gestation.