In vitro cell transformation induced by the pesticide fenarimol

The pesticide fenarimol is capable of transforming BALB/c 3T3 cells in an in vitro model system, and its action resembles a carcinogenic process in vivo. In the absence of metabolic activation, transformed foci are already visible in the standard experimental procedure. The addition of the S9 fraction as an exogenous metabolic system leads to a decrement of cytotoxic effects and the reduction of the transformation rate. The transformed phenotype, however, becomes visible when confluent cells are replated and allowed further cell replication. Transformation effects by fenarimol may be due to both a weak genotoxic activity and/or stronger promoting activity.