D. Ghosh et al., LUTEAL-PHASE OVARIAN ESTROGEN IS NOT ESSENTIAL FOR IMPLANTATION AND MAINTENANCE OF PREGNANCY FROM SURROGATE EMBRYO-TRANSFER IN THE RHESUS-MONKEY, Human reproduction, 9(4), 1994, pp. 629-637
The aim of this study was to investigate whether luteal phase ovarian
oestrogen is required for blastocyst implantation and pregnancy mainte
nance in the rhesus monkey. Preimplantation embryos were retrieved fro
m naturally ovulated, mated embryo donor monkeys. In group I, developm
entally normal, age- and stage-matched embryos were transferred to rec
ipient monkeys showing naturally synchronized ovulatory cycles. Immedi
ately prior to embryo transfer, recipients were subjected to bilateral
ovariectomy, and following transfer they were treated with i.m. injec
tions of either progesterone (group Ia, n = 4), or oestradiol + proges
terone (group Ib, n = 2). Recipient monkeys of group Ic (n = 4) were s
ubjected to sham ovariectomy and vehicle injection. In group Ia, proge
sterone supplementation alone led to three pregnancies and live births
. In group Tb, there was one live birth. In the control group Ic, four
transfers resulted in two live births and one abortion on cycle day 5
8. Analysis of serum progesterone and oestradiol profiles showed that
oestradiol had declined to undetectable levels within 3-5 days after o
variectomy in group Ia recipients, and the area under the curve of ser
um oestrogen concentrations during the periimplantation period (days 1
0-20 after ovulation) were less (P < 0.001) in group Ia compared with
group Ic. There were no changes in the area under the curve among seru
m progesterone concentrations in all the subgroups. In group II, long-
term ovariectomized embryo recipients (n = 4) were primed with oestrad
iol till cycle day 11 of simulated transfer cycle, and received proges
terone treatment from cycle day 10 till the end of the experiment. Of
four transfers, live births were recorded in two cases, while in one c
ase abortion occurred on cycle day 66. Serum oestradiol concentrations
were undetectable during the presumptive peri-implantation period of
pregnancy cycles in group II recipient monkeys. Noyes' dating of endom
etrial samples collected from both groups on days 5-7 after the oestro
gen rise revealed that endometrial histology synchronized well with th
ose found during days 3-5 after ovulation in normal menstrual cycle. W
e conclude that luteal phase ovarian oestrogen is not essential for pr
ogesterone-dependent endometrial receptivity and responses leading to
implantation and pregnancy maintenance in the rhesus monkey.