Submitted January 17, 2002
Returned for revision February 19, 2002
Accepted July 3, 2002
Ovary
Localization and Secretion of Inhibins in the Equine Fetal
Ovaries
Yumiko Tanaka 1,
Hiroyuki Taniyama 2,
Nobuo Tsunoda 3,
Chandana B. Herath 4,
Rie Nakai 1,
Hiromi Shinbo 4,
Natsuko Nagamine 3,
Yasou Nambo 5,
Shun-ichi Nagata 6,
Gen Watanbe 1,
Nigel P. Groome 7,
Kazuyoshi Taya 8*
1 Gifu University
2 Rakuno Gakuen University
3 Shadai Corporation
4 Tokyo University
5 Japan Racing Association
6 Laboratory of Racing Chemistry
7 Oxford Brookes University
8 Tokyo University of Agriculture and Technology
* To whom correspondence should be addressed. E-mail: taya{at}cc.tuat.ac.jp.
Abstract
To clarify the source of inhibins in equine female
fetuses, concentrations of immunoreactive (ir-) inhibin,
inhibin pro-
C and inhibin A in both fetal and
maternal circulation, and in fetal ovaries were measured.
In addition, the localization of inhibin -,
inhibin/activin ßA- and ßB-subunits and the
expression of inhibin - and inhibin/activin
ßA-subunit mRNA in fetal ovaries were investigated
using immunohistochemistry and in situ
hybridization. Concentrations of circulating ir-inhibin,
inhibin pro-C and inhibin A were remarkably
elevated in the fetal than in the maternal circulation
between day 100 and 250 of gestation. Fetal ovaries
contained large amounts of ir-inhibin, inhibin
pro-C and inhibin A. In contrast, these inhibin
forms were undetectable in both the maternal ovaries and
placenta. The inhibin -, inhibin/activin ßA-
and ßB-subunit proteins were localized to enlarged
interstitial cells of the equine fetal ovary. Expression
of inhibin - and inhibin/activin ßA-subunit
mRNAs were also observed in the interstitial cells. We
conclude that the main source of large amounts of inhibins
in fetal circulation is interstitial cells of fetal ovary,
and not of maternal origin. Furthermore, these inhibins
may play some important physiological roles in the
development of gonads in the equine fetus.
Key words:
Ovary •
Pregnancy •
Inhibin
