Effects of aromatizable and nonaromatizable androgens on the sex inversion of red-spotted grouper (Epinephelus akaara) |
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Authors: | Guang-Li Li Xiao-Chun Liu Hao-Ran Lin |
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Institution: | (1) Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, College of Life Sciences, Zhongshan (Sun Yat-Sen) University, Guangzhou, 510275, P. R. China;(2) Fisheries College, Guangdong Ocean University, Zhanjiang, 524025, China |
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Abstract: | The effects of aromatizable 17α-methyltestosterone (MT) and non-aromatizable 17α-methyldihydrotestosterone (MDHT) on sex inversion
in red-spotted grouper, Epinephelus akaara, were investigated. Fish were implanted with MT, MDHT and MT+AI (aromatase inhibitor, AI) respectively for one month. The
results showed that the three treated groups turned into transitional stage with intersex gonads, which contained atretic
oocytes and spermatogenic germ cells at all stages of spermatogenesis. The controls did not change sex. The gonads of more
than half MT-implanted fish were in early transitional stages of sex inversion, whereas those of more than half MDHT and MT+AI-implanted
fish were in late transitional stages of sex inversion. No difference in serum estradiol-17β (E2) levels between the controls and the treated groups were observed, whereas 11-ketotestosterone (11-KT) and testosterone (T)
levels increased in all treated groups. Significantly lower gonadosomatic index (GSI) and gonadal aromatase activity were
observed in the treated groups, which were in accordance with the lower mRNA expression of P450aromA. However, P450aromB mRNA
expression increased in the MT group, while it did not change in the MDHT group. These results suggest that the sex inversion
of red-spotted grouper by MT and MDHT implantation might be due to the suppression of P450aromA gene expression, and resulting
in both the decrease of the ovarian estrogen –secretion, as well as the increase in the 11-KT levels. Furthermore, the main
reason for MT being less effective than MDHT might be due to partial aromatization of MT to estrogen. |
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Keywords: | aromatase inhibitor Epinephelus akaara methyltestosterone methyldihydrotestosterone sex inversion sex steroids |
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