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Gas chromatography-mass spectrometry (GC-MS) has great advantages for analyzing organic/amino acids, which are often targets in efficacy and/or toxicity studies. Although GC-MS has been used for the detection of many metabolic disorders, applications of GC-MS-based metabolomics in pharmacology/toxicology are relatively underdeveloped. We intended to investigate applicability of a GC-MS-based metabolomics approach for toxicological evaluation, and tried to elucidate the mechanism of hydrazine-induced hepatotoxicity. Rats were administered hydrazine chloride orally (120 and 240 mg kg⁻¹), and urine, plasma and liver samples were collected at 24 or 48 h post-dosing. Conventional clinical chemistry and liver histopathology were performed, urine and plasma were analyzed by GC-MS, and metabolic profiles were assessed using chemometric techniques. Principal component analysis score plots showed clear separation of the groups, indicating dose-dependent toxicity and recovery. The mechanism of toxicity was investigated based on semi-quantification data of identified metabolites. Amino acid precursors of glutathione (cystein, glutamate and glycine) and a product of glutathione metabolism (5-oxoproline) were elevated dose-dependently, accompanied with elevation of ascorbate levels. In addition, intermediates of the TCA cycle were decreased, whereas participants of the urea cycle and other amino acids were increased. These alterations were associated with histopathological changes such as fatty degeneration and glycogen accumulation. Application of GC-MS-based metabolomics revealed that oxidative stress and GSH consumption play important roles in the etiology of hydrazine-induced hepatotoxicity, demonstrating that this approach is a useful tool in pharmacology and toxicology for screening, elucidating mode of action and biomarker discovery.

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