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

Abstract

The in vivo estrogenic potency of zearalenone (ZEA), a mycotoxin produced by different strains of Fusarium fungi, and its metabolites (α- and β-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 α-zearalenol and ZEA in rainbow trout ( Oncorhynchus mykiss) were approximately 1/150 and 1/300 to that of estradiol, respectively. Juvenile salmon ( Salmo salar) were exposed to a single intraperitoneal injection of ZEA, α-zearalenol and β-zearalenol (each at 1 and 10 mg/kg) and compared to fish injected with estradiol-17β (E 2; 5 mg/kg) and controls. Using indirect enzyme-linked immunosorbent assay (ELISA) with homologous antibodies, a dose-dependent induction of vitellogenin (Vtg) and eggshell zona radiata proteins ( Zr-proteins) were observed 7 days after exposure to ZEA and α-zearalenol. β-Zearalenol did not elevate plasma Vtg levels, but a non-significant elevation of plasma Zr-proteins levels was observed at the highest dose (10 mg/kg). Generally, α-zearalenol and ZEA possess estrogenic potencies that are approximately 50% compared to that of E 2, and their order of estrogenic potency (in both in vitro receptor competitive binding and in vivo induction of Vtg and Zr-proteins levels) is: α-zearalenol>ZEA>β-zearalenol. 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.