The estrogen receptor in fish and effects of synthetic estrogens in the environment - Ecological and evolutionary perspectives and societal awareness
Abstract: Synthetic hormones are a group of pharmaceuticals used for various human and animal treatments. However, consumption and disposal of these substances have also given rise to negative effects and environmental problems for organisms in the wild which is why these substances have been classified as estrogenic endocrine-disrupting chemicals (EDCs). Studies on the estrogen receptors (ers) and their genes are of particular interest when investigating emerging negative effects from estrogenic EDC contaminants. In vertebrates, the ers are well conserved between organisms and regulate activation and deactivation involved for example in growth, reproduction and development in both males and females. The initial aims of my research presented in this thesis were to show how the duplicated er genes in vertebrates, by studying fish and salmonid species in particular, are distributed, activated or disrupted by both ecological and pharmaceutical challenges. I have worked with three different fish species: Atlantic salmon (Salmo salar); brown trout (Salmo trutta); and roach (Rutilus rutilus) sampled from natural populations in the wild. I show that there is a complex interaction between estrogens and its receptors, depending on which tissues and life stages are investigated. I have also identified multiple ers in salmonids, which could affect their sensitivity to EDC exposure. In the framework of how 17α-ethinylestradiol (EE2) affects fish and the environment we linked exposure of EE2 to changes in behavior and gene expression and as such the consequences it might have for the structure and function of an ecosystem. Because of the recent focus on technical solutions for the removal of pharmaceutical EDCs in the environment a complementary aim was to investigate whether increased knowledge regarding the disposal and usage of EDCs, so called upstream work, could lower use of and prescriptions for the human female contraception EE2. For this I assessed the societal awareness among the main prescribers and decision makers in Sweden on the negative effects release of EE2 has on the environment. I show that providing nurse midwives with more knowledge and information about the negative consequences synthetic hormones have on ecosystems could lead to changes in their consultations practices and their prescriptions of EE2. This, in combination with updated recommendations regarding norms and practice for safe contraceptive care from authorities, could in the future help lower EE2 residues in the environment in the future. To conclude, this thesis identifies key factors for understanding how EDCs affect organisms. I show that ers vary in expression between both life stages and between tissues and that this should be considered when estimating risks for organisms after EDC exposure. This thesis also opens up a new and hitherto unappreciated field in the work surrounding the upstream knowledge and EDCs.
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