Perfluorobutanesulfonate Induces Hypothalamic–Pituitary–Gonadal Axis Disruption and Gonadal Dysplasia of <i>Lithobates catesbeianus</i> Tadpoles

It is uncertain whether exposure to environmental concentrations of perfluorobutanesulfonate (PFBS) disrupts the reproductive endocrine system in amphibian tadpoles. In this study, tadpoles (<i>Lithobates catesbeianus</i>) in G26 stage were treated with different levels of PFBS (0, 1, 3, and 10 μg/L) for 60 days to investigate whether and how PFBS affects the reproductive endocrine system and gonadal development in tadpoles. Tadpole testes exhibited structural damage to germ cells and significantly fewer spermatogonia following PFBS exposure, but the sex ratio remained unaffected. Further, PFBS exposure downregulated transcripts of genes associated with ovarian (<i>figla</i> and <i>nobox</i>) and testicular (<i>sox9</i> and <i>dmrt1</i>) development in tadpoles. Encoding gonadotropin hormone genes were transcriptionally upregulated in the pituitary, and serum gonadotropins (FSH and LH) were elevated. Genes related to testosterone synthesis were transcriptionally upregulated, and serum testosterone concentrations were raised. The transcription of the <i>cyp19a1</i> gene, which is involved in the synthesis of estradiol (E2), was downregulated, leading to decreased levels of serum E2. Furthermore, the transcript level of the vitellogenin gene was downregulated in the liver. Thus, PFBS exposure appears to disrupt the hypothalamic-pituitary-gonadal-liver axis in tadpoles, subsequently impacting gonadal development. The findings of this study indicate that environmental concentrations of PFBS threaten the reproductive endocrine system in amphibians for the first time. This provides important insights for further investigation into the risk that PFBS poses to the stability of the amphibian population.