Submitted September 17, 2003
Returned for revision October 16, 2003
Accepted February 24, 2004
Female Reproductive Tract
Progesterone Promotes Oocyte Maturation, but Not
Ovulation, in Nonhuman Primate Follicles Without a
Gonadotropin Surge
Sherri M. Borman ,
Charles L. Chaffin ,
Kristine M. Schwinof ,
Richard L. Stouffer ,
and
Mary B. Zelinski-Wooten *
* To whom correspondence should be addressed. E-mail: zelinski{at}ohsu.edu.
Abstract
During the peri-ovulatory interval, intrafollicular
progesterone (P) prevents follicular atresia and promotes
ovulation. Whether P influences oocyte quality or
maturation and follicle rupture independent of the
midcycle gonadotropin surge was examined. Rhesus monkeys
underwent controlled ovarian stimulation with recombinant
human gonadotropins followed by (a) Experiment 1: an
ovulatory bolus of hCG alone or with a steroid synthesis
inhibitor (trilostane, TRL), or TRL + the progestin R5020;
or (b) no hCG but rather, sesame oil (vehicle), R5020 or
dihydrotestosterone (DHT). In Experiment 1, the majority
of oocytes remained immature (65 ± 20%) by 12 h
post-hCG. However, the percentage of degenerating oocytes
increased (p<0.05) with TRL (42 ± 22% vs. 0%
controls), but was reduced (p<0.05) by progestin
replacement (15 ± 7%). By 36 h post-hCG, the
majority of oocytes in all three groups reached metaphase
II (MI). In Experiment 2, no evidence of follicle rupture
was observed in the vehicle, R5020 or DHT groups. Despite
the absence of hCG, a significant (p<0.05) percentage of
oocytes resumed meiosis to metaphase I in R5020- (41
± 9) and DHT- (36 ± 15), but not vehicle-
(4 ± 4), treated animals. Only oocytes from
R5020-treated animals continued meiosis in vivo to MII.
More (p<0.05) oocytes fertilized in vitro with R5020 (40%)
than with vehicle (20%) or DHT (22%). Thus, P is unable
to elicit ovulation in the absence of an ovulatory
gonadotropin surge; however P and/or androgens may prevent
oocyte atresia and promote oocyte nuclear maturation in
primate follicles.
Key words:
In vitro fertilization •
Meiosis •
Ovulation •
Ovum •
Progesterone
