Acute cytotoxicity testing with cultured human lung and dermal cells.
An extensive in vitro study with cultured cells was conducted to test the basal cytotoxicity theory. This theory suggests that most chemical injury, at least in vitro, is a manifestation of one or more insults to the basic cellular structures and functions common to mammalian cells. This accounts for the similarity of results in multilaboratory studies. Human fetal lung fibroblasts (HFL1), and human skin fibroblasts (WS1, Detroit551) were studied in culture to evaluate their potential to screen for cytotoxicity. Confluent monolayers were incubated in the absence or presence of increasing concentrations of test chemicals for 24 h, and the MTT assay was used to assess toxicity. Inhibitory concentrations were extrapolated from concentration-effect curves after linear regression analysis. Twenty-nine chemicals were tested with each cell line and the cytotoxicity data compared to rodent and human lethal concentrations. The data suggest that the experimental IC50 values are as accurate predictors of human toxicity as equivalent toxic blood concentrations derived from rodent LD50s. In addition, lung and skin fibroblasts revealed no significant differences among the three cell lines. The results support the conclusion that finite cell lines of human origin have the potential for screening chemicals for human toxicity. In combination with previously published reports, the data suggest that a basal cytotoxic phenomenon may explain the similarity of results among different human cell lines.