A COMPARISON OF THE TOXICITY OF 50 REFERENCE CHEMICALS TO FRESHLY ISOLATED RAINBOW-TROUT HEPATOCYTES AND DAPHNIA-MAGNA

There is a need for rapid and cost-effective in vitro tests or test batteries in aquatic toxicology which could be used as tools in evaluating the toxicity of chemicals. In the present study the toxicity of 50 reference chemicals was evaluated by determining immobility in Daphnia magna (24 h incubation) and Rb-86-leakage in freshly isolated rainbow trout hepatocytes (3 h incubation). Regression analysis of the data on the EC(50) for Daphnia and EC(50) for the rubidium leakage in hepatocytes showed a correlation of 0.71 (p < 0.0001). The slope of the regression line (0.68) differed markedly from a 1:1 correlation. Daphnia was more sensitive to the chemicals than hepatocytes and the discrepancy between the two tests increased with increasing toxicity of the chemicals. A comparison of the data from the hepatocyte test with published data on the toxicity of the reference chemicals to cultured mammalian hepatocytes (24 h incubation), indicated that the lower sensitivity of the fish hepatocytes compared to Daphnia is not due to the shorter incubation time used in the hepatocyte test. A comparison of the data from the Daphnia test with published data on the toxicity of the reference chemicals to various mammalian cells, showed a similar discrepancy between the Daphnia test and the cellular tests as in the case of the comparison between the Daphnia test and the rainbow trout hepatocyte test; indicating that the Daphnia test in general is more sensitive than conventional cellular cytotoxicity tests. It is concluded that further studies, using more sensitive endpoints than rubidium leakage, are needed before it can be decided whether or not freshly isolated rainbow trout hepatocytes are suitable in routine toxicity testing.