Fish model for assessing the in vivo estrogenic potency of the mycotoxin zearalenone and its metabolites

The in vivo estrogenic potency of zearalenone ZEA., a mycotoxin produced by different strains of Fusarium fungi, and its metabolites a- and b-zearalenol., have been studied in fish. Estrogenicity was evaluated using an in vitro competitive receptor binding assay and in vivo induction of vitellogenesis and zonagenesis, two estrogen receptor ER.-mediated responses that are integral aspects of fish oogenesis. The ER binding affinities of a-zearalenol and ZEA in rainbow trout Oncorhynchus mykiss. were approximately 1r150 and 1r300 to that of estradiol, respectively. Juvenile salmon Salmo salar. were exposed to a single intraperitoneal injection of ZEA, a-zearalenol and b-zearalenol each at 1 and 10 mgrkg. and compared to fish injected with estradiol-17b E2; 5 mgrkg. and controls. Using indirect enzyme-linked immunosorbent assay ELISA. with homologous antibodies, a dose-dependent induc- tion of vitellogenin Vtg. and eggshell zona radiata proteins Zr-proteins. were observed 7 days after exposure to ZEA and a-zearalenol. b-Zearalenol did not elevate plasma Vtg levels, but a non-significant elevation of plasma Zr-proteins levels was observed at the highest dose 10 mgrkg.. Generally, a-zearalenol and ZEA possess estrogenic potencies that are approximately 50% compared to that of E2, and their order of estrogenic potency in both in vitro receptor competitive binding and in vivo induction of Vtg and Zr-proteins levels. is: a-zearalenol)ZEA)bzearalenol. Our results show that blood plasma analysis of Vtg and Zr-proteins levels provides a suitable in vivo fish model for assessing the estrogenic potencies of ZEA and its metabolites.