Crosstalk between the thyroid hormone and androgen axes during reproductive development in Silurana tropicalis

- Perchlorate affected transcription of androgen- and TH-related genes.
- Androgen- and TH-related mRNA levels were stage and tissue specific.
- Perchlorate has secondary androgenic endocrine-disrupting properties.

The objectives of this study were to examine the effects of potassium perchlorate (KClO4) treatment on androgen- and thyroid hormone (TH)-related transcript levels during gonadogenesis in the frog Silurana tropicalis. Androgen- and TH-related gene expression was examined in gonad-mesonephros complex (GMC) and liver tissues at stage NF 56 and stage NF 60. These stages of development coincide with the period of sexual differentiation. Real-time RT-PCR analyses revealed that androgen- and TH-related transcript levels in the GMC and liver of stage NF 56 and NF 60 frogs are responsive to KClO4 exposure during prometamorphosis. An increase in srd5α2 mRNA levels in hepatic tissues of KClO4-treated NF 56 tadpoles suggests an important role for hepatic tissues in androgen metabolism. Gene transcript differences highlight possible stage- and tissue-specific sensitivities to KClO4. A greater number of TH- and androgen-related transcriptional changes were discerned in the hepatic tissues compared to the gonads, and overall fewer transcriptional changes were observed in stage NF 60 tadpoles compared to stage NF 56 larvae. Perchlorate suppressed somatic and hind-limb development during the 96-d exposure period. Treatment with KClO4 had no significant effect on sex ratios, however a notable reduction in the percentage of males (33.3% M: 66.7% F) in the highest KClO4 concentration (107 μg/L) was observed. Overall, these findings suggest that KClO4 has secondary androgenic disrupting properties in addition to its known primary thyroid hormone-disrupting role.