The Influence of Environmental Estrogens on Early-life Stage Zebrafish Development
Zielinska, Katarzyna Anna
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Endocrine disrupting compounds (EDCs) including bisphenol A (BPA) and genistein may induce estrogenic effects in organisms. Genistein is a naturally occurring plant compound found mainly in soy products while BPA is used in the production of plastics and resins. Given their widespread environmental presence, simultaneous exposure to both compounds is conceivable. This study investigated the effects of BPA or/and genistein on early development of zebrafish. Zebrafish is a widely used model for developmental biology and toxicology as it has many conserved developmental programs also found in mammals. Concentration dependent toxicity of both BPA and genistein was observed based on increased mortality, reduced heart rate, reduced hatching and presence of morphological malformations in the treated embryos/larvae up to 120 hpf. Most of the BPA and genistein mixtures indicated additive effects. Some observations revealed that synergistic and antagonistic interactions may also occur. This study was the first to investigate the effects of EDCs mixtures on the liver ultrastructure of a developing organism. Stereological methods allowed for objective, quantitative description of the organ phenotypes and statistical analysis of the data. Cytological alterations observed following treatments included changes in the volume of the hepatocytes, mitochondrial, RER and glycogen. Particularly affected were size and shape of mitochondria. Considerably fewer morphological changes in mixtures treated larvae may indicate antagonistic interactions between BPA and genistein. Based on the alterations in the RER volume synergistic interactions could also be inferred. Estrogenic potential of BPA or/and genistein was investigated based on their ability to increase vitellogenin 1 mRNA (vtg1) expression level. Vitellogenin is a yolk precursor protein produced in the liver of oviparous vertebrates in response to the activation of ERs. Genistein showed higher potential to induce vtg1 expression than BPA. The estrogenicity of the mixtures was enhanced, although not significantly, when compared to the treatments with individual EDCs.