impact of 17-α-ethinylestradiol on immune function and reproductive gene expression in zebrafish (danio rerio): implications for aquaculture of important commercial fish species

In the present study, we detected changes in immune parameters, antioxidant enzymes, and reproductive gene expression in adult female zebrafish (danio rerio) exposed to different concentrations of 17-ethinylestradiol (ee2). a total of 300 healthy adult females were divided into 15 aquaria, which were allocated to five treatments with three replicates. the zebrafish were exposed to varying concentrations of ee2 including 0.5 (t0.5), 5 (t5), 50 (t50), and 500 (t500) ng l⁻¹, along with an unexposed control group (ultrapure water, t0) for 21 days. after 21 days, lysozyme activity, total immunoglobulin, superoxide dismutase, malondialdehyde (mda), alkaline phosphatase (alp), alanine aminotransferase, aspartate aminotransferase (ast) and reproductive gene expression were evaluated.  the results showed that exposure to ee2 caused a significant decrease in lysozyme activity, and total immunoglobulin levels, but had no significant effect (p>0.05) on the sod activity. the mda level was significantly higher in the high-dose hormone treatments than in the control group (p<0.05). different ee2 concentrations had a significant impact on alp and alt activities and they increased in fish exposed to ee2 compared to the control (p<0.05). the expression levels of gnrh2, gnrh3, gnrhr2, gnrhr3, lhβ, and fshβ genes significantly increased (p < 0.05) in the females. in contrast, the expression of the hsd3b gene significantly decreased (p>0.05). significant decreases (p<0.05) were also observed in the expression of lhcgr and fshr genes in the female zebrafish. in conclusion, our results demonstrate that different concentrations of ee2 can disrupt steroidogenesis by interfering with the expression of genes related to sex steroid levels in the female broodstock of zebrafish.