Joint acute and endocrine disruptive toxicities of malathion, cypermethrin and prochloraz to embryo-larval zebrafish, Danio rerio

It remains a daunting challenge to determine ecotoxicological risks of exposure to mixtures of endocrine disrupting chemicals (EDCs) in environmental toxicology. In the present study, we investigated acute and endocrine disruptive toxicities of cypermethrin (CPM), malathion (MAL), prochloraz (PRO) and their binary mixtures of MAL + CPM and MAL + PRO to the early life stages of zebrafish. In the acute lethal toxicity test, three pesticides exhibited different levels of toxicity to zebrafish larvae, and the order of toxicity was as follows: CPM > PRO > MAL. The binary mixture of MAL + CPM displayed a synergistic effect on zebrafish larvae after exposure for 24, 48, 72 and 96 h. However, binary mixture of MAL + PRO showed an antagonistic effect. To evaluate the estrogenic effect, the expression of genes in the hypothalamic-pituitary-gonadal axis was assessed after zebrafish embryos were exposed to CPM, MAL, PRO and their binary mixtures from blastula stage (1 h post-fertilization, 1 hpf) to 14 dpf (14 d post-fertilization). Our data indicated that the transcription patterns of many key genes (vtg1, vtg2, era, erβ1, erβ2, cyp19a1a and cyp19a1b) were affected in hatched zebrafish after exposure to CPM, MAL and PRO. Moreover, following exposure to binary mixtures of 1000 μg/L MAL +4 μg/L CPM and 1000 μg/L MAL +900 μg/L PRO, the gene expressions were significantly changed compared with the individual pesticides. Our data provided a better understanding of bidirectional interactions of toxic response induced by these pesticides.