GENERATION OF HYDROPEROXIDES IN ISOLATED RAT HEPATOCYTES AND HEPATIC MITOCHONDRIA EXPOSED TO HYDROPHOBIC BILE-ACIDS

Background & Aims: The mechanisms causing liver injury in cholestatic diseases are unclear. The hypothesis that accumulation of hydrophobic bile acids in hepatocytes during cholestasis leads to generation of ox ygen free radicals and oxidative injury was tested. The aim of this st udy was to determine if hydrophobic bile acid toxicity is associated w ith increased hydroperoxide generation in isolated rat hepatocytes and mitochondria. Methods: Hepatocytes were exposed to taurochenodeoxycho lic acid (TCDC; 0-2000 mu mol/L) or taurocholic acid (TC; 1000 mu mol/ L), and cellular injury, intracellular hydroperoxide generation, and t hiobarbituric acid-reacting substances (TEARS) were measured. Isolated mitochondria were incubated with 400 mu mol/L chenodeoxycholic acid o r 400 mu mol/L cholic acid, and hydroperoxide generation was measured fluorometrically. Results: Hepatocyte injury, hydroperoxide generation , and TEARS increased over 4 hours on exposure to TCDC but not TC. Hyd roperoxide generation preceded hepatocyte injury and accumulation of T EARS. Preincubation of hepatocytes with the antioxidant, d-alpha-tocop heryl succinate, completely abrogated cellular injury, hydroperoxide, and TEARS generation. Hydroperoxide generation was increased in mitoch ondria exposed to chenodeoxycholic acid. Conclusions: Intracellular ge neration of hydroperoxides by mitochondria appears to be an early even t in hydrophobic bile acid-induced hepatocyte toxicity. Antioxidants m ay be of benefit in cholestasis.