A CCl₄/CHCl₃ interaction study in isolated hepatocytes: Non‐induced and phenobarbitalpretreated cells

The purpose of this study was to evaluate an isolated hepatocyte model for predicting the in vivo hepatotoxicity of carbon tetrachloride (CCl₄) and chloroform (CHCl₃), alone and in combination. Response surface methodology (RSM) was used to analyze and describe the data. The interaction was evaluated for % initial K⁺ (cell injury) and % LDH leakage (cell death) in non‐induced (untreated) and phenobarbital‐pretreated suspended hepatocytes. CCl₄ and CHCl₃ were delivered alone and in combination in dimethyl sulfoxide (DMSO) to suspended hepatocytes. The maximum observed no‐effect level (MONEL) for CCl₄ in non‐induced cells was 1.0 mM (LDH and K⁺). In induced cells, the MONEL was 0.25 mM (K⁺) and 0.5 mM (LDH). The MONEL for CHCl₃ in non‐induced cells was 5.0 mM (LDH and K⁺) and in induced cells was 0.5 mM (K⁺) and 1.0 mM (LDH). Phenobarbital pretreatment enhanced the toxicity of both CCl₄ and CHCl₃, alone and in combination. RSM analysis of the % initial K⁺ and % LDH for CCl₄ and CHCl₃ in combination in non‐induced and induced cells showed a greater than additive interaction. The isolated hepatocyte model appears to be a promising system for evaluating the toxicity of chemical mixtures and predicting their in vivo effects.