OPTIMIZING ANIMAL MODELS AND EXPERIMENTAL DESIGNS FOR ENDOCRINE DISRUPTOR RESEARCH AND TESTING

Growing evidence suggests that environmental chemicals can disrupt normal endocrine functions, causing developmental and reproductive abnormalities in fish and wildlife. This has raised concerns about potential human health risks. Consequently, US legislation now mandates the Environmental Protection Agency (EPA) to create and validate a screening program to identify chemicals in food and water that may act as endocrine disruptors. In response, the EPA proposed the Endocrine Disruptor Screening Program, which employs both in vitro and in vivo test systems to identify harmful chemicals for humans and ecologically significant species. However, the endocrine system is highly sensitive to various experimental factors, such as diet and the genetic background of the test animals. To ensure accurate results in endocrine disruptor research, it is crucial to minimize or eliminate factors that contribute to experimental variation. Standard laboratory animal diets, for instance, contain varying levels of phytoestrogens that can mimic the effects of both endogenous and exogenous estrogens. Additionally, studies have shown that some commonly used outbred mice and rats exhibit lower sensitivity to estrogenic substances compared to certain inbred strains. Thus, selecting appropriate biological models and diets that offer optimal sensitivity and specificity is essential for endocrine disruptor studies. This issue introduces 11 papers that delve into critical experimental design considerations and review current laboratory animal and in vitro models used in endocrine disruptor research. Careful selection of animal models and experimental design parameters will minimize confounding variables, enhance the reproducibility of results, and lead to more reliable and relevant test systems.