Development of a flow-through system for the fish embryo toxicity test (FET) with the zebrafish (Danio rerio).

The acute fish test is still a mandatory component in chemical hazard and risk assessment. However, one of the objectives of the new European chemicals policy (REACH - Registration, Evaluation, Authorization and Restriction of Chemicals) is to promote non-animal testing. For whole effluent testing in Germany, the fish embryo toxicity test (FET) with the zebrafish (Danio rerio) has been an accepted and mandatory replacement of the fish test since January 2005. For chemical testing, however, further optimization of the FET is required to improve the correlation between the acute fish test and the alternative FET. Since adsorption of the test chemical to surfaces may reduce available exposure concentrations, a flow-through system for the FET using modified commercially available polystyrene 24-well microtiter plates was developed, thus combining the advantages of the standard FET with those of continuous delivery of test substances. The advantages of the design presented include: small test footprint, availability of adequate volumes of test solution for subsequent chemical analysis, and sufficient flow to compensate for effects of non-specific adsorption within 24h. The flow-through test system can also be utilized to conduct longer-term embryo larval fish tests, thus offering the possibility for teratogenicity testing.

Bioconcentration, metabolism and toxicity of substituted anilines in the zebrafish (Brachydanio rerio).

The LC50 (96 h) values and the bioconcentration factors (BCF) for nine anilines (aniline; 2-, 3-, 4-chloroaniline; 2-, 3-, 4-nitroaniline; 2,4- and 3,4-dichloroaniline) in the zebrafish (Brachydanio rerio) were determined. Biotransformation products of anilines in the zebrafish were analyzed by HPLC. The aim of the investigations was to find relationships between accumulation/elimination/metabolism and toxicity on the one hand and between chemical structure and biotransformation on the other. We found a good correlation of log BCF and of log Pow with log LC50. This concurs with the assumption that the internal dose determines the toxicological effect. All anilines investigated, with the exception of 2- and 4-nitroaniline, were transformed into the corresponding acetanilides. The toxicity of the compounds was not altered by biotransformation. A comparison of the extent of acetylation confirms the supposition that substituents in the ortho position sterically hinder acetylation.