© 1996 Oxford University Press
research-article |
Evidence Suggesting the 58-kDa Acetaminophen Binding Protein Is a Preferential Target for Acetaminophen Electrophile1
*Toxicology Program, Departments of Pharmaceutical Sciences Storrs, Connecticut 06269-2092
Toxicology Program, Departments of Molecular and Cell Biology, University of Connecticut Storrs, Connecticut 06269-2092
Received December 15, 1995; accepted March 6, 1996
Acetaminophen is an analgesic and antipyretic which causes liver toxicity in humans and experimental animals with overdose. Acetaminophen (APAP) covalent binding to a cytosolic protein of approximately 58 kDa (58–ABP) has been associated with target organ toxicity. Since hepatic content of 58–ABP varies, studies were conducted to determine if this influences APAP binding to other target proteins. In the liver, the amount of 58–ABP varied with individual male CD-1 mice, but in kidneys of the same mice there was no such variability in 58–ABP content. All male A/J mice tested had comparatively little detectable 58–ABP in liver cytosol. Similarly, female CD–1 mice had low 58–ABP content compared to males; however, administration of testosterone propionate to females significantly increased 58-ABP content in liver cytosol. At 4 hr after challenge of mice from the above-described groups with 600 mg APAP/kg, cytosolic covalent binding to proteins was determined by Western blot analysis with anti–APAP antibody. The Western blots were then stripped of antibody and blocking agents and reprobed with antibody prepared against purified 58–ABP (anti–58–ABP). In the liver, the level of APAP bound to the 58-ABP target corresponded with 58–ABP content. In cases where 58–ABP was poorly expressed, APAP adducts to other protein targets were more prominently detected. In the kidneys of the male CD–1 mice 58–ABP arylation by APAP varied little among animals, reflecting the relatively consistent levels of renal 58–ABP. These data suggest that binding to the 58–ABP may spare other potential targets of APAP electrophile attack and support a role of the 58–ABP as a preferred target of APAP electrophile in cytosol.