AN IN-VITRO TOXICITY TESTING STRATEGY FOR THE CLASSIFICATION AND LABELING OF CHEMICALS ACCORDING TO THEIR POTENTIAL ACUTE LETHAL POTENCY

An in vitro test battery is described which consists of five systems u sing different types of cells: (1) bovine sperm cells, (2) Balb/c 3T3 cells, (3) primary cultures of rat hepatocytes, (4) primary cultures o f 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 cytoto xicity, selective cytotoxicity and interference with selected cell-spe cific functions (Seibert et al., 1992). During the current phase of ev aluation 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 appropr iate assays for inclusion in a hierarchical approach to testing. Based on the experience with this test battery, a preliminary stepwise appr oach is proposed for the classification of chemicals according to thei r acute lethal potency. The principle steps and candidate tests are: ( 1) determination of cytotoxic activity (cytolethal and cytostatic)-spe rm cells, 3T3 cell line; (2) determination of hepatocyte-specific cyto toxicity and of the role of bioactivation for cytotoxic activity-cultu res of hepatocytes and 3T3 cells; and (3) determination of the potenti al of chemicals to interfere with electrically excitable membranes-mus cle cell cultures.