EVIDENCE FOR COMMON BINDING OF ACETAMINOPHEN AND BROMOBENZENE TO THE 58-KDA ACETAMINOPHEN-BINDING PROTEIN

Acetaminophen (APAP) toxicity has been closely associated with covalen t binding to a cytosolic protein of approximately 58 kDa (58-ABP). To determine if metabolites of other toxicants might also selectively tar get this protein, studies were conducted with bromobenzene (BrB). Mice were given phenobarbital (80 mg/kg/d x 4 d) and were killed 4 h after challenge with 800 mg BrB/kg. Liver cytosols from BrB-treated or naiv e mice were incubated with an APAP activating system. Cytosolic fracti ons were analyzed for APAP binding by Western blotting with anti-APAP antibody. Binding to 58-ABP was selectively decreased in liver cytosol from BrB-treated mice while binding to other targets was minimally af fected. Western blotting of the same samples with anti-58-ABP antisera showed that this decrease in binding did not result from diminished 5 8-ABP content. HPLC analysis of APAP-N-acetyl cysteine conjugate forma tion in vitro indicates that APAP activation was not altered in the in cubates with cytosol from BrB-treated mice. These results suggest that the 58-ABP may be a common target for electrophiles in reactive inter mediate toxicity.