Abstract
In the present study, we implanted 2-year-old female red-spotted grouper, Epinephelus akaara, with a non-steroidal aromatase inhibitor (AI), fadrozole, in the breeding season and examined changes in gonadal histology, serum sex steroids, aromatase activities and P450 aromatase (P450arom) gene expression in gonads after AI implantation. Aromatase inhibitor at doses from 0.1 to 10.0 mg kg−1 BW induced a sex inversion and completion of spermatogenesis up to the functional male phase, but doses of 1.0 and 10.0 mg kg−1 BW AI produced more males than 0.1 mg kg−1 BW AI. Serum estradiol-17β (E2) levels decreased, but 11-ketotestosterone (11-KT) levels increased significantly in all the AI-implanted groups, whereas testosterone (T) levels increased significantly only in the 1.0 mg kg−1 BW AI-implanted group. Aromatase activities and P450arom gene expression in gonads were inhibited significantly in the AI-implanted groups, which was in accordance with the decrease in serum E2 levels. These results suggested the optimal dose of AI to induce sex inversion to be 1.0 mg kg−1 BW. Furthermore, the sex inversion induced by AI may be attributed to the inhibition of P450arom gene expression and aromatase activity and the resultant decrease in the biosynthesis of endogenous E2. Meanwhile, the elevated 11-KT levels were also associated closely with the occurrence of sex inversion in protogynous red-spotted grouper.
Published Version
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