Thyroid endocrine disruption in male zebrafish following exposure to binary mixture of bisphenol AF and sulfamethoxazole

- Bisphenol AF (BPAF) alters expression of genes related to thyroid endocrine system.
- Sulfamethoxazole (SMX) increased endocrine disruption potential of BPAF.
- Thyroxine (T4) concentration was significantly increased in mixture group.
- Expressions of trh and tshβ in brain were regulated as a feedback response of T4.

Thyroid endocrine disruption by bisphenol AF (BPAF) alone or in combination with sulfamethoxazole (SMX) exposure was evaluated in adult male zebrafish. Changes in thyroid gene transcription were examined using microarrays and were linked to effects on thyroxine hormone production and transcription of genes related to the hypothalamic-pituitary-thyroid axis. BPAF alone or in combination with SMX affected genes related to thyroid hormone production and receptor activity, thyroid gland development, and deiodinase activity. Increases in thyroxine levels, and gene transcription were more pronounced in the BPAF and SMX mixture group than in the BPAF group. Significant down-regulation of trh and tshβ genes in the brain suggested a negative feedback response resulting in increased thyroxine levels. The present study indicated that BPAF exposure alone alters transcription of genes associated with the thyroid endocrine system, and combination with SMX could increase the endocrine disrupting effect of BPAF.