A B S T R A C T Background: Propylthiouracil (PTU) administration is associated with several cases of hepatotoxicity, especially in children. The mechanism(s) of PTUinduced hepatotoxicity is obscure. In the current study, we aimed to assess the effect of PTU on hepatocytes mitochondria in different experimental models. Methods: Mice were treated with PTU (10, 20, 40, 80, and 100 mg/kg, i.p) then, the liver mitochondria were isolated and evaluated. Moreover, liver mitochondria were isolated from

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... normal mice and incubated with increasing concentrations of PTU (10 µM-1 mM). Mitochondrial dehydrogenases activity, mitochondrial membrane potential, mitochondrial swelling, and mitochondrial adenosine triphosphate (ATP) content were monitored. Results: PTU hepatotoxicity was biochemically evident in mice by increased serum biomarkers of liver injury. PTU also caused a decrease in mitochondrial dehydrogenases activity, increased mitochondrial swelling, depleted mitochondrial ATP, and caused mitochondrial depolarization both in vitro and in vivo. Conclusion: Our data suggest mitochondrial dysfunction as a mechanism for PTU-induced hepatotoxicity.