EVIDENCE SUGGESTING THE 58-KDA ACETAMINOPHEN BINDING-PROTEIN IS A PREFERENTIAL TARGET FOR ACETAMINOPHEN ELECTROPHILE

Acetaminophen is an analgesic and antipyretic which causes liver toxic ity in humans and experimental animals with overdose. Acetaminophen (A PAP) 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 am ount of 58-ABP varied with individual male CD-1 mice, but in kidneys o f the same mice there was no such variability in 58-ABP content. All m ale A/J mice tested had comparatively little detectable 58-ABP in live r cytosol. Similarly, female CD-1 mice had low 58-ABP content compared to males; however, administration of testosterone propionate to femal es significantly increased 58-ABP content in liver cytosol. At 4 hr af ter 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 str ipped of antibody and blocking agents and reprobed with antibody prepa red 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 c ases 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, reflectin g 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 ta rget of APAP electrophile in cytosol. (C) 1996 Society of Toxicology