Exploring gene expression dynamics in zebrafish embryos exposed to trenbolone: A 96-Hour RNA-seq Study

Endocrine active substances present significant risks to both human health and the environment, particularly by disrupting essential endocrine-regulated functions like organism development and reproductive capacity. Regulatory frameworks mandate animal testing for chemical risk assessment, placing specific emphasis on suspected endocrine disruptors. For example, aquatic vertebrate chronic toxicity testing is mandatory at a chemical tonnage of 100 t/y using the Fish Early Life Stage (FELS, OECD TG 210) test. However, suspected endocrine disruptors are subjected to testing from a lower tonnage threshold of 10 t/y. Currently, the assessment of endocrine effects adheres to an OECD Conceptual Framework (CF) that employs a tiered approach. This entails evaluating existing data for potential endocrine effects (Level 1), conducting mechanism of action-specific in vitro studies (Level 2), and undertaking in vivo mechanistic screening studies (Level 3). If screening studies indicate potential endocrine disruption, further investigation is conducted using a Fish Sexual Development Test (FSDT, OECD TG 234) to clarify (anti)estrogenic, (anti)androgenic, and steroidal effects (EAS effects) in fish. Nevertheless, this testing process is resource-intensive, time-consuming, and involves extensive animal use. Therefore, this study aims to identify the androgenic activity of trenbolone using the zebrafish embryo model. Trenbolone, a synthetic anabolic steroid, primarily exerts its effects by binding to androgen receptors. The data collected will be compared with those obtained from androstenedione exposure to zebrafish embryos.