Vitellogenin Gene Expression and Sex Steroid Levels as Biomarkers in Yellowfin Seabream (Acanthopagrus latus) Exposed to Bisphenol-A

The egg yolk precursor protein vitellogenin (VTG) has proven to be a useful biomarker, used to identify organisms exposed to estrogenic compounds. We investigated variations in the VTG gene expression pattern and plasma sex steroid hormones concentrations in the yellowfin Seabream, Acanthopagrus latus, (A. latus) by various doses of bisphenol-A (BPA) exposure for 7 and 14 days. We developed a quantitative real time polymerase chain reaction (RT-PCR) assay for the expression of VTG gene in A. latus. The dose-response pattern of VTG gene expression in A. latus exposed to various doses of BPA was characterized. In order to design RT-PCR primers specific to A. latus VTG, a partial sequence of the VTG gene was obtained. The RT-PCR assay was effective in detecting increased VTG gene expression in A. latus exposed to BPA. It also demonstrated that the VTG expression was affected by BPA in a dose and time-dependent manner. Plasma testosterone (T) levels were decreased in the treated fish in comparison with those found in the control group, when they were exposed to 100 µg/g of BPA and 2 µg/g of E2. In contrast, the plasma levels of 17β-estradiol (E2) were significantly increased in a dose-dependent manner. The results suggest that VTG mRNA quantification can provide a sensitive and early signal in the detection of estrogens in marine wildlife. It also indicated that BPA could lead to an imbalance of sex steroid hormones with potentially harmful consequences on sexually immature male A. latus.