Transcript profiles and triiodothyronine regulation of sex steroid- and thyroid hormone-related genes in the gonad-mesonephros complex of Silurana tropicalis

In amphibians, the main role of thyroid hormones (THs) is to regulate metamorphosis; however, there is evidence that THs also affect gonadal sexual differentiation. In this study, Silurana (Xenopus) tropicalis tadpoles were exposed to triiodothyronine (T3; 0, 0.5, 5 and 50 nM), the bioactive form of THs for 48 h. Real-time RT-PCR analyses in the gonad-mesonephros complex (GMC) revealed that TH- and androgen-related genes were positively regulated, while estrogen receptor 13 was negatively regulated by T3. Together, these results are in agreement with the masculinizing effect of THs in amphibians. Profiles of TH- and sex steroid-related genes in the GMC during metamorphosis of S. tropicalis suggest that THs are important regulators of sex steroid-related gene expression in the GMC. This study provides evidence that the GMC is a target of THs but that a complex interplay exists between THs and sex steroids during gonadal sexual development. (C) 2010 Elsevier Ireland Ltd. All rights reserved.