IMMUNOHISTOCHEMICAL LOCALIZATION OF ACETAMINOPHEN IN TARGET TISSUES OF THE CD-1 MOUSE - CORRESPONDENCE OF COVALENT BINDING WITH TOXICITY

Administration of hepatotoxic doses of acetaminophen (APAP) to mice re sults in necrosis, not only of liver cells but of renal proximal tubul es and bronchiolar and olfactory epithelium. In the liver, covalent bi nding is localized to the centrilobular hepatocytes which later underg o necrosis. This study was undertaken to compare the cellular distribu tion of bound APAP in all four major target tissues with that of cytoc hrome P4502E1 (a P450 isoenzyme commonly associated with APAP bioactiv ation), with emphasis on the cell types which later undergo necrosis, Tissues were collected from mice at selected times after APAP administ ration (600 mg/kg, po) and fixed by microwave irradiation for immunohi stochemistry, or in formalin for histopathological study, Immunohistoc hemical localization of bound APAP was performed on 5-mu m paraffin se ctions using an affinity-purified anti-APAP antibody. Similar tissues from naive mice were used for immunohistochemical localization of cyto chrome P4502E1 (using a polyclonal sheep anti-P4502E1 antibody), Posit ive staining with both the anti-APAP and the anti-P4502E1 antibodies w as similar in distribution, being present in the cell types which beco me damaged by APAP in all four target tissues, These results demonstra te that covalent binding and subsequent necrosis are localized in comm on with cytochrome P4502E1, suggesting that, as in the liver, toxicity in extrahepatic targets is also related to the ability of these tissu es to activate APAP in situ. (C) 1995 Society of Toxicology.