title: Zebrafish (Danio rerio) as a model to study developmental effects of endocrine disruption: molecular mechanisms, as well as persistence and reversibility of effects
creator: Baumann, Lisa Annie
subject: 570
subject: 570 Life sciences
description: The present study aimed to investigate the reversibility of endocrine disruption in zebrafish  (Danio rerio) at different effect levels. For this purpose, three different endocrine disrupting  chemicals (EDCs) were chosen according to their different modes of action. 17!-  Ethinylestradiol (EE2), a semi-synthetic estrogen is the most popular substance in oral  contraceptives and is regularly measured in surface waters. 17ß-trenbolone is an anabolic  steroid, which binds with high affinity to the androgen receptor. The substance is used in  industrial animal farming and sports as muscle growth promoter. Prochloraz is a popular  fungicide with multiple modes of action. Its main effect on the endocrine system is that it  inhibits the enzyme aromatase, which is essential for the conversion of androgens into  estrogens. The effects of those three EDCs were assessed by performance of exposure  experiments with developing zebrafish. After exposure of 60 days (from fertilized egg to  sexual differentiation), half of the fish were continuously exposed until 100 days post hatch  and the other half was held in clean water. In addition, this project focuses on assessing the  correlation between different levels of biological organization. For this purpose, five effect  levels with different ecological relevance were investigated: (1) population level: sex ratio;  (2) individual level: growth; (3) organ/cell level: histology of gonads; (4) protein level:  vitellogenin (VTG) induction and (5) mRNA level: aromatase (cyp19b) expression in brain.  The three different EDCs investigated in this study showed strong impact on the sexual  development of zebrafish at all effect levels at environmentally relevant concentrations. For  trenbolone and prochloraz we could only find tendencies of reversibility, most effects  remained unchanged after 40 days of depuration in clean water. Despite different underlying  mechanisms, these substances produce an irreversible and considerable drift of the sex ratio  towards males, as well as permanent effects on growth, VTG and aromatase levels. A clear  reversibility of those effects could only be shown for EE2. Even at population level the  impact of the semi-synthetic estrogen was reversible.  These results show that the sexual development of zebrafish is a fragile process that can easily  be disrupted permanently by substances that are found in the environment. Moreover, the  results indicate that even a periodic exposure to those EDCs can cause severe impairment for  wildlife and humans.
date: 2013
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/14512/1/Baumann%20Dissertation.pdf
identifier: DOI:10.11588/heidok.00014512
identifier: urn:nbn:de:bsz:16-heidok-145124
identifier:   Baumann, Lisa Annie  (2013) Zebrafish (Danio rerio) as a model to study developmental effects of endocrine disruption: molecular mechanisms, as well as persistence and reversibility of effects.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/14512/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng