Hepatotoxicity of ketoconazole in Sprague-Dawley rats: glutathione depletion, flavin-containing monooxygenases-mediated bioactivation and hepatic covalent binding

Abstract

1. This study has examined ketoconazole (KT)-induced hepatotoxicity in vivo and in vitro, using male Sprague-Dawley rats with [3 H]KT (1.5 µCi mg − 1) at 40 and 90 mg KT kg − 1 doses. Blood and liver samples were collected from 0 to 24 h for alanine aminotransaminase (ALT), glutathione (GSH) and covalent binding analyses. 2. Covalent binding occurred as early as 0.5 h, peaked at 2 h (0.026 ± 0.01 nmol KT mg − 1 protein) and 8 h (0.088 ± 0.04 nmol KT mg − 1 protein) for 40 and 90 mg KT kg − 1 doses, respectively. ALT levels increased at 0.5 h for the 40 and 90 mg KT kg − 1 doses (44.3 and 56.4 U ml − 1, respectively) relative to control, 22.7 U ml − 1. At 24 h, the 90 mg KT kg − 1 dose reduced hepatic GSH levels from 9.92 ± 1.1 to 4.76 ± 0.3 nmol GSH mg − 1 protein. 3. The role of the flavin-containing monooxygenases (FMO) utilized Sprague-Dawley microsomes with 1, 10 and 100 µM [3 H]KT. Maximum covalent binding occurring at 100 µM KT. Heat inactivation of microsomal FMO significantly decreased covalent binding by 75%, whereas 1 mM GSH significantly reduced covalent binding by 65%. 4. Thus, KT-induced hepatotoxicity is dose- and time-dependent and appears to be FMO mediated, in part, to metabolites that may react with protein and, possibly, GSH.