W5 PM Toxicity of Complex Mixtures
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 321-323

(LIN-1117-836728) Additive and non-additive interactions of binary xenoestrogen mixtures in zebrafish (Danio rerio).

Lin, L¹, Janz, D^{1, 2}, ¹ Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada² Veterinary Biomedical Science, Saskatoon, SK, Canada

ABSTRACT- This study evaluated effects of binary mixtures of two common xenoestrogens on sex ratios, vitellogenin (Vtg) induction, heat shock protein 70 (hsp70) expression, gonadal cell death, and breeding success in a partial lifecycle test with zebrafish (Danio rerio). Fish were exposed from 2 to 60 days post - hatch (dph) to environmentally relevant concentrations of 17 - ethinylestradiol (EE₂) (1 or 10 ng/l nominal; EE1 or EE10), 4 - nonylphenol (NP) (10 or 100 g/l nominal; NP10 or NP100), binary combinations of EE₂ and NP (EE1+NP10, EE1+NP100, EE10+NP10, or EE10+NP100) or solvent control (acetone; 0.1% v/v) in a static-renewal system with replacement every 48h. At 60 dph, 40 fish from each treatment were euthanized for analysis, while the remainder were raised in clean water for reproductive studies. Significant increases in weight-at-length of treatments EE10, NP100, EE1+NP10, EE10+NP10 and EE10+NP100 were observed when compared to the control. Delayed gametogenesis in males and females in EE10, EE10+NP10 and EE10+NP100 were observed, while no testicular tissues were detected in groups EE1, EE1+NP10 and EE1+NP100. Significant decreases in total number of eggs collected from treatments EE10 and EE10+NP100 were observed when compared to solvent controls. No eggs were produced from EE10+NP10. Hatchability of eggs was significantly lower in EE10 when compared to the control. There were no significant differences in whole-body hsp70 expression among treatments. Analysis of gonadal cell death will be performed to determine any potential correlation with hsp70 expression. Overall, our data suggest the effects of EE₂ and NP are additive up to a threshold level of EE10+NP10, while at EE10+NP100, NP appeared to antagonize the action of EE₂.

Key words: zebrafish, xenoestrogen, mixture, reproduction