Thyroid disruption and developmental toxicity caused by triphenyltin (TPT) in zebrafish embryos/larvae

The adverse effects of triphenyltin (TPT) on aquatic systems have attracted much attention because TPT is widely used and prevalent in aquatic environments. Here, zebrafish embryos/larvae were exposed to TPT (0, 0.039, 0.39, and 3.9 nM; 0, 15, 150 and 1500 ng/L) for 7 or 14 days to determine its toxic effects on the hypothalamic-pituitary-thyroid (HPT) axis. The results showed that whole-body total T4 and T3 levels were significantly decreased, which was accompanied by the significant upregulation of the expression of the dio1, dio2 and ugt1ab genes after exposure to TPT for 7 and 14 days. Genes related to thyroid hormone synthesis (crh, tshβ, nis, tpo and tg) were upregulated at both 7 and 14 days after TPT exposure. This might have been due to the positive feedback regulation of the HPT axis, which is caused by a decrease in thyroid hormone in the whole body in zebrafish. In addition, the survival rates and body lengths were reduced after treatment with TPT for 7 and 14 days. This indicated that TPT caused adverse effect on the development of zebrafish embryos/larvae. In summary, the results suggested that TPT caused thyroid disruption and developmental toxicity in zebrafish larvae.