Protocols for the evaluation of toxicity of chemicals to fish are established for only a few fish species. They moreover focus mostly on effect parameters that are easily visible by eye. The analysis of gene expression, i.e. the abundance of mRNA, of certain biomarker genes is a promising approach to close this gap: Gene expression analysis can be customized for different species of fish and uncover broad spectrum of “hidden” reactions in an organism to chemical exposure.
We have established a palette of biomarker genes for brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) to assess the effects of diverse chemicals, such as pharmaceuticals or pesticides. The biomarker genes reflect different cellular stress responses, such as metal- or oxidative stress, endocrine disruption, biotransformation and immunoregulation. Biomarker genes can be analyzed in different tissues of the fish, depending on the aim of the analysis.
A gene expression analysis can be performed on fish, which were captured…
- … upstream and downstream from a waste water treatment plant (WWTP); the impact by the WWTP can be evaluated in this way
- … in different distances from a source; this allows to capture the impact of a gradient of contaminants
- … at a particular site in order to subsequently compare the data with fish from reference sites or from a laboratory in order to analyze the status of the fish.
Gene expression analysis can furthermore serve as an additional effect parameter for regular toxicity tests, such as the fish acute toxicity test (OECD 203), the fish embryo acute toxicity test (OECD 236), the Fish Early-life Stage Toxicity Test (OECD 210) and the Fish Short-term Toxicity Test on Embryo and Sac-fry Stages (OECD 212).
Gene expression analysis in fish cells
Together with researchers from Eawag we are working on the establishment of gene expression analyses in fish cell lines, which were previously exposed to water samples. The aim of these developments is to record sub-lethal effects in the cell lines instead of in fish, thereby eliminating the need to capture and sacrifice fish.