Long-term effects of a binary mixture of perfluorooctane sulfonate (PFOS) and bisphenol A (BPA) in zebrafish (Danio rerio)

• Previous in vitro studies have reported the potential of perfluorooctane sulfonate (PFOS) to increase the toxicity of other compounds. Given the complex nature of mixtures of environmental pollutants in aquatic systems together with the persistent and bioaccumulative properties of PFOS, this study aimed at evaluating the long-term effects and toxicity-increasing behavior of PFOS in vivo using the zebrafish (Danio rerio). Fish were maintained in flow-through conditions and exposed to single and binary mixtures of PFOS and the endocrine disruptor bisphenol A (BPA) at nominal concentrations of 0.6, 100 and 300 mu g/L and 10, 200 and 400 mu g/L, respectively. F1 and F2 generations were evaluated from 0 to 180 days post-fertilization (dpf) and F3 generation was evaluated from 0 to 14 dpf. Survival was documented in all generations, whereas growth, fecundity, fertilization rate, histological alterations (in liver, thyroid and gonads) and vitellogenin (Vtg) induction in males were evaluated for Fl and F2 generations. Data for growth were collected at 30, 90 and 180 dpf and data for histological evaluations and Vtg induction were analyzed at 90 and 180 dpf. No significant effects on survival were seen in the Fl generation in any treatment following 180 d exposure: however, in the F2 generation, 300 mu g/L PFOS both alone and in combination with BPA (10, 200 and 400 mu g/L) induced 100% mortality within 14 dpf. PFOS (0.6 and 300 mu g/L) did not increase the Vtg-inducing potential of BPA (10, 200 and 400 mu g/L) in a binary mixture. In contrast, binary mixtures with 300 mu g/L PFOS suppressed the Vtg levels in Fl males at 90 dpf when compared to single BPA exposures. Whereas the lowest tested PFOS concentration (0.6 mu g/L) showed an estrogenic potential in terms of significant Vtg induction, Vtg levels were generally found to decrease with increasing PFOS-exposure in both Fl and F2 generations. In Fl generation, BPA-exposure was found to increase Vtg levels in a concentration-dependent manner. Histological analyses of Fl and F2 fish revealed hepatocellular vacuolization, predominantly in males, following PFOS-exposure both alone and in combination with BPA. Hepatotoxicity by PFOS might explain the suppressed Vtg response seen in PFOS-exposed Fl and F2 males. PFOS-exposed fish also showed granulomas, mainly in the liver. Given previous reports of the immunosuppressive potential of PFOS, the granulomas could be a consequence of a PFOS-induced reduction of the immune response potential. In conclusion, the hypothesis that the presence of PFOS increases the endocrine potential of BPA could not be confirmed in zebrafish. Adverse effects on liver structure and survival were only seen at concentrations well above ecologically relevant concentrations; however, the decline in survival rates following PFOS-exposure seen over generations again documents the importance of long-term studies for the investigation of persistent environmental pollutants.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Perfluorooctane sulfonate

Bisphenol A

Long-term

Mixture

Vitellogenin

Zebrafish

Biology

Biologi

Publikations- och innehållstyp

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