OECD Test No. 249: Fish Cell Line Acute Toxicity ‑ The RTgill‑W1 cell line assay
The ecotoxicology team at Staphyt is committed to upholding the core principles of the 3Rs (Replacement, Reduction, and Refinement) in all aspects of animal testing and actively practices this commitment in our daily laboratory operations. Consequently, we maintain a consistent and proactive engagement in the identification, evaluation, and implementation of new methods to traditional animal testing.
We are pleased to announce that a significant step has been taken in this commitment: the successful implementation of OECD Guideline 249, officially titled ‘Fish Cell Line Acute Toxicity – The RTgill-W1 Cell Line Assay’ in our portfolio.
The assay is a short-term cell viability test, typically conducted over a 24- to 72-hour exposure period. It allows for the evaluation of adverse effects on the gill cells by monitoring three key cellular endpoints or markers, which collectively indicate the overall cell health and integrity:
- Integrity of Lysosomal Membrane: Neutral red assay stain allows the assessment of viable cells by their ability to incorporate and retain the vital dye in their lysosomes. Damage to the lysosomal membrane is an early indicator of cellular stress.
- Metabolic Activity (Mitochondrial Function): Measured using the Alamar Blue (AB) assay (or a similar resazurin-based assay). This marker assesses the metabolic reduction of the dye by intracellular enzymes, providing a proxy for the energy status and overall viability of the cells.
- Integrity of Cell Membrane: Determined using the CFDA-AM assay. This endpoint measures the loss of intracellular fluorescein from the cytoplasm, which only occurs if the cell membrane is compromised (a sign of necrosis or severe damage).
By evaluating these three distinct cellular endpoints, the RTgill-W1 assay provides a comprehensive profile of acute cellular toxicity. This streamlined in vitro approach is designed to:
- Predict fish acute toxicity in product testing;
- Range-finding and pre-screening before conducting a full fish acute or other fish-based toxicity test;
- Generation of toxicity information to be used for hazard assessment in combination with other lines of evidences (e.g., Quantitative Structure Activity Relationships (QSAR), weight of evidence (WoE)), within Integrated Testing Strategy (ITS)/Integrated Approach to Testing and Assessment (IATA)
If the aim is to predict, from the cell viability data, the lethal concentration of acute chemical exposure to fish, first, all EC50 values should be reported and of these, the lowest is used as most conservative estimate. This EC50 value is then taken as the predicted 96 h LC50 value in fish.
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