Quantitative determination of urinary lipid metabolites by high pressure liquid chromatography as indicators of menadione-induced in vivo lipid peroxidation

The one- and two-electron-reduction reactions of menadione result in the generation of reactive oxygen species which are believed to mediate the cytotoxicity of this xenobiotic. The induction of lipid peroxidation in liver and isolated hepatocytes occurs in response to the menadione-mediated formation of reactive oxygen species. However, studies on the effects of menadione on the urinary excretion of lipid metabolites have not been conducted. The effect of a single oral dose of 60 mg menadione/kg to rats on the urinary excretion of the lipid metabolites malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) has been examined over 48 h post-treatment. The urinary metabolites were identified by gas chromatography-mass spectrometry and quantitated by high pressure liquid chromatography. Time-dependent increases in the urinary excretion of the four metabolites were observed after menadione administration. Over the 48 h of the study, the menadione-induced urinary excretion of MDA, FA, ACT, and ACON increased by approximately 1.5-, 2.0-, 1.7-, and 3.2-fold, respectively, relative to control animals. The data were expressed in nmoles/kg body weight/4.5 h. The results clearly demonstrate that menadione increases the urinary excretion of four lipid metabolites. These metabolites may have widespread applicability as biomarkers of altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics which induce enhanced lipid peroxidation. The non-invasive methods offer advantages over most other methods for assessing oxidative stress in vivo.