Endocrine disruption in thicklip grey mullet (Chelon labrosus) from the Urdaibai Biosphere Reserve (Bay of Biscay, Southwestern Europe).

Endocrine disruptors (EDs) interfere with the development and functioning of the endocrine system, causing reproductive disturbance in aquatic wildlife. The aim of the present work was to determine the presence of EDs in sediments and to investigate possible exposure and effects of EDs in the estuary of the Urdaibai Biosphere Reserve (Gernika) in comparison with the Arriluze marina. For this, gonad histology, plasma vitellogenin (VTG) protein levels and mRNA levels of vitellogenin (vtg), cyp19 aromatases, estrogen receptor (er) and retinoid X receptor (rxr) were studied in Chelon labrosus. The presence of alkylphenols (APs) in fish bile was also assessed. In sediments, estrogenic hormones were below the detection limit and levels of bisphenol A were very low. In Gernika organotin compounds were low but in Arriluze levels of up to 12 µg/g were found. Moderate levels of APs and phthalate levels of up to 8 µg/g were found in sediments. In fish, a high prevalence up to 33% of intersex gonads was found in Gernika, whereas only one intersex was found in Arriluze. Accordingly, mullets from Gernika showed higher concentrations of APs in bile. VTG protein levels were detected not only in females but also in some undifferentiated, male and intersex fish. mRNA of vtg was detected in one male from Gernika. mRNA of er and rxr showed significant differences between seasons. In conclusion, the present study demonstrated that C. labrosus from the Urdaibai estuary were exposed to EDs and showed clear signs of endocrine disruption.

Sandwich immunoassay for determination of vitellogenin in golden grey mullet (Liza aurata) serum as a field exposure biomarker.

Vitellogenin (VTG) is a protein produced in the liver of oviparous animals in response to oestrogens. Abnormal production of VTG by males, therefore, is used as a biological indicator of exposure to xeno-oestrogens. In this study, a sandwich-ELISA for measuring VTG in Liza aurata (golden grey mullet) was developed and validated. Plasma VTG was purified from 17beta-oestradiol-injected immature individuals of mullet, by size-exclusion and ion-exchange chromatography. Polyclonal antibodies against VTG were raised in rabbits. A sensitive immunoassay was developed for measurement of vitellogenin in L. aurata serum, reaching a quantification limit of 0.01 microg mL(-1) and a dynamic range from 0.02 to 2 microg mL(-1). The assay is specific, because high levels (>100 microg mL(-1)) of carp (Cyprinus carpio), goldfish (Carassius auratus), tilapia (Oreochromis niloticus), tench (Tinca tinca), rainbow trout (Oncorhynchus mykiss), European eel (Anguilla anguilla) and frog (Rana perezi) purified VTG, give negligible responses. The assay was used to analyse plasma samples from wild mullet.