Comparison of testing acute toxicity on embryo of zebrafish, Brachydanio rerio and RTG-2 cytotoxicity as possible alternatives to the acute fish test

The present study compares two possible alternative methods to replace the acute fish test. Fertilized eggs of zebrafish, Brachydanio rerio were used to investigate the acute toxicity of chemicals. Different toxicological endpoints such as coagulation of the eggs, development of gastrulation, number of somites, development of organs, circulation, heartbeat, otolithanlage and pigmentation have been examined during the embryonic development of zebrafish within the first 48 h. Differences to the normal development were measured by these endpoints. Chemicals have been examined in a preliminary approach with respect to their cytotoxicity on the RTG-2 cells (Rainbow Trout Gonad). The vitality of cells was measured by Neutral Red-and MTT assay. Urea, sodium chloride, 2-nitroanisole, 3,4-dichloroaniline, 4-nitrophenol, phenol, 2,4-dinitrophenol, dinitro-ortho-cresole, carbaryl and malathion were used as compounds with different modes of actions. The results of the cytotoxicity tests with Neutral Red uptake (NR50) and MTT (MTT50) have been compared with data of zebrafish, Brachydanio rerio. We could show that the embryo test in most cases is more sensitive than the acute toxicity test with adult zebrafish and in all cases is more sensitive than the RTG-2 cell test. Therefore, considering the wide range of possibilities the embryo of zebrafish offers, we think that the embryo test is a very good candidate to replace the acute fish test. Whether the cytotoxicity test with RTG-2 cells is also an alternative requires further, more detailed studies.