ABILITY FOR BIOSYNTHESIS OF PROGESTERONE AND DHEA BY UMBILICAL CORD
ERYTHROCYTES: A ROLE FOR MAINTENANCE OF PREGNANCY
Peh KL, Loganath A, Chew PCT, Wong YC, Wong PC
University
Department of Obstetrics & Gynaecology, National University Hospital,
Singapore
Objective: In order to establish the hitherto
undescribed steroidogenic ability of human cord blood erythrocytes, the
present study was conducted to examine the metabolic transformation of [7n-3H]pregnenolone
to [3H]progesterone as well as [3H]dehydroepiandrosterone
(DHEA).
Methods:
Sonicated preparations of plasma-free erythrocytes obtained from
umbilical cord blood of normal pregnant women at term were incubated with
[7n-3H]pregnenolone as substrate. [3H]P and [3H]DHEA
were characterized by the reverse-isotope dilution technique.
Results:
Radiochemically pure [3H]P and [3H]DHEA
acetate persisted on recrystallization in all experiments of viable
erythrocytes with mean specific activities that ranged from 120.9-278.7
dpm/mg for [3H]P and 5.4-10.5 dpm/mg for [3H]DHEA. No
such metabolites were evident in control experiments with heat-denatured
preparations. The efficiency of enzymic conversion ranged from 0.54 - 1.26%
for [3H]P and 2.8 x 10-2 – 5.4 x 10-2% for
[3H]DHEA.
Conclusion:
The results reveal for the first time that umbilical cord erythrocytes are steroidogenic and
possess the enzymic capacity for P and DHEA biosynthesis; thereby serving
an alternative source of P for maintenance of pregnancy and DHEA for
oestrogen formation needed by the developing fetus.