Effects of mestranol on estrogen receptors expression in zebrafish

The estrogen receptor (ER) genes, which encode a group of important ligand-activated transcriptional factors, can modulate estrogen-target gene activities. Zebrafish ( Danio rerio ) have three ER receptor genes, esr1 , esr2a , and esr2b . In this study, we examined the mRNA expression levels of these ER receptors after treatment with mestranol (EE3ME). Zebrafish larvae were exposed to 0.01, 0.1, 1, and 10 mg/L from 6 hours post-fertilization (hpf) and the mRNA expression levels of the ER genes were determined at 24, 48, 72 and 96 hpf. Treatment with mestranol led to a significant stimulation of esr1 mRNA expression at lower concentration and reached maximum at 72 hpf, however, the esr1 mRNA levels were reduced at higher mestranol concentration during exposure. The gene expression of esr2b was markedly decreased and the esr2a remained unaffected at all concentration in the duration. Altogether, these results suggested mestranol might cause the disruption of endocrine activities in fish by mediating ER genes expression.