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Vol. 51 No. 8, 2012
Homeostasis of Circulating Androgen Levels in the Breeding Male Three-spined Stickleback Gasterosteus aculeatus
Yi-Ta Shao1, Rüdiger W. Schulz2, and Bertil Borg1,*
1Department of Zoology, Stockholm Univ., Stockholm S-10691, Sweden. E-mail:yita.shao@zoologi.su.se
2Department of Biology, Utrecht Univ., Utrecht 3508 TC, the Netherlands. E-mail:R.W.Schulz@uu.nl
Yi-Ta Shao, Rüdiger W. Schulz, and Bertil Borg (2012) Androgens
are important for stimulating male characters, but excessively high
levels may suppress the immune system, and in many animals, circulating
levels are homeostatically controlled by feedback mechanisms.
However, it was shown that there is no compensation of plasma androgen
levels in hemi-castrated threespined stickleback Gasterosteus
aculeatus. In this study, we investigated to what extent
androgens levels are homeostatically regulated in the breeding male
three-spined stickleback, and whether aromatization of androgens plays
a role in this. To that end, breeding male sticklebacks were
either completely castrated, hemicastrated, or sham-operated, and then
implanted with different doses of 11-ketoandrostenedione (11KA) and
testosterone (T) or with the aromatase inhibitor (AI), fadrozole.
Hemi-castration alone diminished androgen levels, while complete
castration almost completely removed them. Low doses of 11KA and
T increased plasma androgen levels in castrated but not in
sham-operated fish. Both low and high doses of 11KA increased
plasma 11-ketotestosterone (11KT) in hemi-castrated fish, whereas only
the high dose of 11KA did so in sham-operated fish. If
aromatization plays a role in homeostatic mechanisms, androgen levels
would be expected to rise in sham-operated fish treated with the
AI. However, this was not the case. The reduction in plasma
androgen levels in fully mature hemi-castrated fish suggests that the
remaining testis was unable to further increase its
steroidogenesis. However, both 11KA and T treatments increased
plasma levels much less in sham-operated fish than in castrated ones,
indicating that homeostatic mechanisms are present and act to prevent
excessively high plasma androgen levels.
Key words: Steroid, RIA, Homeostasis, Feedback, Stickleback.
*Correspondence: Tel: 46-8164082. Fax: 46-8167715. E-mail:bertil.borg@zoologi.su.se
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