Vitellogenin induction in juvenile rainbow trout (Oncorhynchus mykiss) after long term water exposure to 4-Nonylphenol and 17-estradiol

There is increasing concern about man-made chemicals in the aquatic environment that are able to mimic the action of the steroid hormone, 17-estradiol (E2) and to disturb normal physiology and endocrinology of living organisms. One of the most sensitive response to the xenobiotic estrogens in fish is the induction of the egg-yolk precursor vitellogenin (Vtg). Vtg synthesis is normally limited to reproductive female fish but in male or immature fish, who have the Vtg gene, expression of the protein can be induced by exposure to the xeno-estrogens. and may thus serve as a reliable biomarker for xenobiotic estrogen. Using Vtg induction, previous in vitro and in vivo experiments have shown the estrogenicity of the alkylphenolic compound 4-NonylPhenol (4-NP). However, few in vivo data are available with continuous water exposure. We exposed juvenile rainbow trout (Oncorhynchus mykiss) to 100, 50 and 10 µg/L of 4-NP (>99% purity) and to 250 ng/L of 17-estradiol (nominal concentration) using a flowthrough contamination system. Durations of exposure were three, six and eight weeks. Concentrations of 4-NP and E2 were measured by HPLC and ELISA respectively. Quantification of the plasma Vtg was made by a specific rainbow trout Vtg ELISA using anti-salmo antibody. After three weeks of exposure, we observed a significant vitellogenin induction with both oestradiol and the highest concentration of nonylphenol. / Nous avons exposé des truites juvéniles au 4nonylphenol (100 , 50 , 10 µg/L) et au 17 beta oestradiol (250 ng/L) en mode d'exposition continue. Au bout de 3 semaines nous observons une induction de vitellogenine pour les truites exposées à l'oestradiol ou à la plus forte concentration en nonylphenol.