Sex-specific responses of the reproductive system of zebrafish (Danio rerio) to electrolysis

Adult zebrafish (Danio rerio) were electrolyzed at different current densities to explore the effects of electrolysis on their reproductive system, especially on embryo production, and to uncover the molecular mechanism of changes in sex hormone and vitellogenin (VTG) levels. The results showed that embryo reproduction of zebrafish was reduced at a current density of 0.64 A/m(2) after 28 days of exposure. In addition, the 17 beta-estradiol concentration significantly decreased and the testosterone concentration increased in female zebrafish above 0.53 A/m(2). However, opposite trends were observed in male zebrafish. The VTG concentration was reduced considerably in the livers of female zebrafish in the 0.64 A/m(2) electrolysis group (p < 0.05). In addition, the mRNA expression of hormone-regulating genes was significantly altered in female and male zebrafish when the current density was greater than 0.53 A/m(2), and their change trends were sex-dependent. The genes expression levels of vtg1 and esr1 were downregulated in female zebrafish. However, the gene expression of esr1 and cyp19a was upregulated in male zebrafish. These changes were related to disruption in the hormone balance and VTG levels of adult zebrafish. Thus, electrolysis could cause masculinization of female zebrafish and feminization of male zebrafish. Nonetheless, there were few influences on the hormone levels and reproduction rate of adult zebrafish at the threshold of 0.26 A/m(2). Thus, the current density of electrolysis needs to be controlled within a specific range to reduce its harmful effects on the reproductive system of aquatic animals.