Induction of hepatic estrogen-responsive gene transcription by permethrin enantiomers in male adult zebrafish

Despite recent studies on enantioselectivity in acute aquatic toxicity and biodegradation of some pyrethroid pesticides, including permethrin (PM), enantiomer-specific estrogenic activity has been the subject of limited research. In this study, real-time quantitative RT-PCR was adopted to investigate induction of hepatic expression of mRNA of selected genes in male adult zebrafish after short-term exposure to PM enantiomers. The PM enantiomers were completely separated by a chiral HPLC column. The in vivo study found that a 2-day exposure to 100 ng/l PM racemate and its enantiomers was sufficient to stimulate transcription of two vitellogenin (vtg) genes, while 250 ng/l exposure significantly induced gene transcription in a pattern and content similar to that of the control (50 ng/l 17β-estradiol (E2)). Significant differences were detected between the enantiomers in induction of hepatic gene transcription. At exposure level of 500 ng/l, the response to the (−)-trans enantiomer was 2.6 and 1.8 times greater than the (+)-trans enantiomer based on zebrafish vtg1 and vtg2 mRNA induction (p < 0.05), respectively. Of the four enantiomers, the (−)-trans enantiomer showed the greatest estrogenic activity, with a relative activity 4-fold higher than the 50 ng/l E2 group. The results strongly suggested the occurrence of significant enantioselectivity in estrogenic activity of PM enantiomers. It would appear from our results and previous studies that using chiral pesticide as a single compound would increase the environmental risk of chronic toxicity, such as endocrine disruption, to humans and wildlife.