In vitro assessment of cytotoxicity and carcinogenic potential of chemicals: Evaluation of the cytotoxicity induced by 58 metal compounds in the Balb/3T3 cell line

A new, mechanistically based, in vitro strategy involving Balb/c 3T3 clone A31-1-1 mouse embryo fibroblasts has been proposed for the determination of the carcinogenic potential of inorganic chemicals, in order to establish p riority of metal compounds to be tested and, whenever possible, to compare the in vitro results with the corresponding in vivo data. As a first step i n this research this study reports on the cytotoxic effects of 58 metal com pounds in the Balb/3T3 cell line. After harmonisation and standardisation o f the Balb/3T3 protocol, cells were exposed for 72 hours to a fixed dose (1 00 muM) of 58 individual compounds. The cytotoxicity induced by some metal compounds was found to be related to their chemical form (for example, Cr(N O3)(3) and Na2CrO4), suggesting that the Balb/3T3 cell line is a valuable c ellular model in relation to this aspect of metal speciation. The results o f the systematic study on the metal-induced cytotoxic effects in the Balb/3 T3 cell line could be arbitrarily classified into three groups according to the degree of cytotoxicity. Group I includes 26 species that induced no ob servable effect or only a slight cytotoxic effect Group II includes 13 meta l compounds that exhibited an obvious degree of cytotoxicity; and Group III includes 19 metal species that displayed a strong cytotoxic response. Meta l compounds of Groups II and III are considered to be of the highest priori ty for setting of dose-effect relationships for a subsequent in vitro study on metal-induced concurrent cytotoxicity and morphological transformation in the Balb/3T3 cell line.