Fluorinated analogues as mechanistic probes in valproic acid hepatotoxicity: hepatic microvesicular steatosis and glutathione status

Chem Res Toxicol. 1995 Jul-Aug;8(5):671-82. doi: 10.1021/tx00047a006.


It is postulated that the hepatotoxicity of valproic acid (VPA) results from the mitochondrial beta-oxidation of its cytochrome P450 metabolite, 2-propyl-4-pentenoic acid (4-ene VPA), to 2-propyl-(E)-2,4-pentadienoic acid ((E)-2,4-diene VPA) which, in the CoA thioester form, either depletes GSH or produces a putative inhibitor of beta-oxidation enzymes. In order to test this hypothesis, 2-fluoro-2-propyl-4-pentenoic acid (alpha-fluoro-4-ene VPA) which was expected to be inert to beta-oxidative metabolism was synthesized and its effect on rat liver studied in comparison with that of 4-ene VPA. Similarly, the known hepatotoxicant 4-pentenoic acid (4-PA) and 2,2-difluoro-4-pentenoic acid (F2-4-PA) were compared. Male Sprague-Dawley rats (150-180 g, 4 rats per group) were dosed ip with 4-ene VPA (0.7 mmol/kg per day), 4-PA (1.0 mmol/kg per day), or equivalent amounts of their alpha-fluorinated analogues for 5 days. Both 4-ene VPA and 4-PA induced severe hepatic microvesicular steatosis ( > 85% affected hepatocytes), and 4-ene VPA produced mitochondrial alterations. By contrast, alpha-fluoro-4-ene VPA and F2-4-PA were not observed to cause morphological changes in the liver. The major metabolite of 4-ene VPA in the rat urine and serum was the beta-oxidation product (E)-2,4-diene VPA. The N-acetylcysteine (NAC) conjugate of (E)-2,4-diene VPA was also found in the urine. Neither (E)-2,4-diene VPA nor the NAC conjugate could be detected in the rats administered alpha-fluoro-4-ene VPA. In a second set of rats (3 rats per group), total liver GSH levels were determined to be depleted to 56% and 72% of control following doses of 4-ene VPA (1.4 mmol/kg) and equivalent alpha-fluoro-4-ene VPA, respectively. Mitochondrial GSH remained unchanged in the alpha-fluoro-4-ene VPA treated group but was reduced to 68% of control in the rats administered 4-ene VPA. These results strongly support the theory that hepatotoxicity of 4-ene VPA, and possibly VPA itself, is mediated largely through beta-oxidation of 4-ene VPA to reactive intermediates that are capable of depleting mitochondrial GSH.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anticonvulsants / toxicity*
  • Fatty Acids, Monounsaturated / metabolism
  • Fatty Acids, Monounsaturated / toxicity*
  • Fatty Liver / chemically induced*
  • Fatty Liver / pathology
  • Gas Chromatography-Mass Spectrometry
  • Glutathione / metabolism*
  • Liver / chemistry
  • Liver / drug effects*
  • Liver / metabolism
  • Liver / pathology
  • Male
  • Mitochondria, Liver / metabolism
  • Pentanoic Acids / metabolism
  • Pentanoic Acids / toxicity*
  • Rats
  • Rats, Sprague-Dawley
  • Valproic Acid / analogs & derivatives
  • Valproic Acid / metabolism
  • Valproic Acid / toxicity*


  • 2,2-difluoro-4-pentenoic acid
  • 2-fluoro-2-propyl-4-pentenoic acid
  • Anticonvulsants
  • Fatty Acids, Monounsaturated
  • Pentanoic Acids
  • 2-propyl-4-pentenoic acid
  • Valproic Acid
  • 4-pentenoic acid
  • Glutathione