Endocrine-active compound evaluation: qualitative and quantitative histomorphological assessment of zebrafish gonads after bisphenol-A exposure.

There is great social concern about the risk involved from exposure to BPA as an endocrine disrupter in humans, as well as the possible repercussion of this chemical on the environment. In this study, the short-term effects of BPA at a gonadal level were assessed by means of different biomarkers in a model animal organism in vogue, the zebrafish (Danio rerio). For this purpose, 60 female zebrafish aged 16 weeks were used. These were exposed for 14 days in aquariums (following OECD Directive no.204) to BPA concentrations of 1, 10, 100 and 1000 μg/L, in addition to a control batch. After the exposure period, the zebrafish were sacrificed and samples taken for a histopathological study by light and electron microscopy and morphometric analysis. During the fourteen days of exposure, water samples were taken from the aquariums to analyze the BPA levels. The BPA concentration in the fish and the water was determined by LC-MS/MS. The gonads of the zebrafish exposed to the BPA had a normal external appearance and there were no variations in their size or body weight. An accumulation of BPA was produced in the zebrafish tissues, and this increased as the BPA concentration to which the fish were exposed did. In the histopathological and morphometric studies, multiple alterations were observed in the zebrafish ovaries, particularly highlighting the vacuolization of the follicular cytoplasm, a great degeneration of all the cell components, and an important increase in the percentage of atretic follicles as from concentrations of 100 and 1000 μg/L of BPA, verified by morphometry. These data indicate that morphological endpoints are sufficiently sensitive to individuate early effects of environmental concentration of BPA on gonads after two weeks of exposure.