The interactive toxicity of CHCL₃ and BRCCL₃ in precision-cut rat liver slices

The interactive toxicity of two nontoxic concentrations of chloroform (CHCl₃and bromotricchloromethane (BrCCl₃ was examined in precision-cut rat liver slices. Liver slices were prepared from male Sprague-Dawley rats (220-250 g) pretreated with phenobarbital for 4 days. Toxicants were administered 1 hr apart. Intracellular K⁺ levels were similar to untreated controls in slices treated with 0.2 mM CHCl₃ or 0.125 μ1 (0.25 mg, 1.26 μmol) BrCCl₃ alone, indicating that these concentrations were nontoxic. However, addition of both toxicants, irrespective of order, resulted in a time-dependent loss of intracellular K⁺ which was significant at 9 hr following administration. This was interpreted as evidence of synergistic toxicity. Cytochrome P450 loss was significant as early as 3 hr following exposure to BrCCl₃ alone or when added with CHCl₃ This loss may be attributed to BrCCl₃ suicide inactivation of cytochrome P450. Centrilobular hepatocytes may be more susceptible to the interactive toxicity of CHCl₃ and BrCCl₃ Activity of enzymes found predominantly in this area was significantly decreased in slices exposed to both toxicants relative to controls. Conversely, activity of enzymes found predominantly in the periportal region was similar to that of untreated and treated controls. Inter active toxicity of BrCCl₃ and CHCl₃ was not a consequence of increased lipid peroxidation or depletion of slice glutathione content. Further studies need to be conducted to elucidate the mechanisms mediating the interactive toxicity of BrCCl₃ and CHCl₃.