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 ba tteries in aquatic toxicology which could be used as tools in evaluati ng 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 o n the EC(50) for Daphnia and EC(50) for the rubidium leakage in hepato cytes showed a correlation of 0.71 (p < 0.0001). The slope of the regr ession line (0.68) differed markedly from a 1:1 correlation. Daphnia w as more sensitive to the chemicals than hepatocytes and the discrepanc y between the two tests increased with increasing toxicity of the chem icals. A comparison of the data from the hepatocyte test with publishe d data on the toxicity of the reference chemicals to cultured mammalia n 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 refer ence chemicals to various mammalian cells, showed a similar discrepanc y between the Daphnia test and the cellular tests as in the case of th e comparison between the Daphnia test and the rainbow trout hepatocyte test; indicating that the Daphnia test in general is more sensitive t han conventional cellular cytotoxicity tests. It is concluded that fur ther studies, using more sensitive endpoints than rubidium leakage, ar e needed before it can be decided whether or not freshly isolated rain bow trout hepatocytes are suitable in routine toxicity testing.