An in vitro toxicity testing strategy for the classification and labelling of chemicals according to their potential...

An in vitro test battery is described which consists of five systems using different types of cells: (1) bovine sperm cells, (2) Balb/c 3T3 cells, (3) primary cultures of rat hepatocytes, (4) primary cultures of rat muscle cells, and (5) co-cultures of microcarrier-attached rate hepatocytes and Balb/c 3T3 cells. This combination of in vitro systems covers various aspects of cellular toxicity and permits determination of the intrinsic activity of chemicals with respect to general cytotoxicity, selective cytotoxicity and interference with selected cell-specific functions (Seibert et al., 1992). During the current phase of evaluation the different test systems are used in parallel, resulting in in vitro toxicity profiles which are the basis (a) for interpretation with respect to toxic potential, and (b) for the selection of appropriate assays for inclusion in a hierarchical approach to testing. Based on the experience with this test battery, a preliminary stepwise approach is proposed for the classification of chemicals according to their acute lethal potency. The principle steps and candidate tests are: (1) determination of cytotoxic activity (cytolethal and cytostatic)-sperm cells, 3T3 cell line; (2) determination of hepatocyte-specific cytotoxicity and of the role of bioactivation for cytotoxic activity-co-cultures of hepatocytes and 3T3 cells; and (3) determination of the potential of chemicals to interfere with electrically excitable membranes-muscle cell cultures.