Acetaminophen Nephrotoxicity in the CD-1 Mouse. II. Protection by Probenecid and AT-125 without Diminution of Renal Covalent Binding

Abstract

Acetaminophen (APAP) administration (600 mg/kg, ip) to 18-hr fasted, 3-month-old male CD-1 mice results in necrosis of the convoluted renal proximal tubules with a corresponding elevation of plasma urea nitrogen (BUN). Administration of the γ-glutamyl transpeptidase inhibitor,L-(αS,5S)-α-amino-3-chloro-4,5-dihydroxy-5-isoxazoleacetic acid (AT-125) (50 mg/kg, ip), to mice 30 min before APAP significantly diminished the APAP-induced histopathologic damage and BUN elevation. Administration of the organic-anion transport inhibitor, probenecid (150 mg/kg, ip), 30 min before APAP challenge also protected against the APAP-induced elevation of BUN and detectable histopathologic changes. By contrast, pretreatment of mice with the cysteine conjugate β-lyase inhibitor, (aminooxy)acetic acid (100 mg/kg, ip), 1 hr before APAP did not alter nephrotoxicity. None of the pretreatments altered the APAP-induced elevation of plasma sorbitol dehydrogenase activity, nor were there any detectable changes in liver histopathology after APAP challenge. Despite the protective effects of both probenecid and AT-125 against nephrotoxicity, they did not affect either the level of immunochemically detectable covalent binding to protein or the depletion of renal glutathione at 4 hr after APAP. Thus, the protection appears independent of effects on renal APAP uptake or activation and indirectly suggests that an APAP–glutathione conjugate may contribute to the observed nephrotoxicity.