Characterization of urinary metabolites from [1,2,methoxy-13C]-2-methoxyethanol in mice using 13C nuclear magnetic resonance spectroscopy.

2-Methoxyethanol (2-ME) is an industrial solvent that induces developmental and testicular toxicity in laboratory animals. Oxidation of 2-ME to 2-methoxyacetic acid (2-MAA) is required for the generation of these adverse effects. The urinary metabolites of 2-ME were investigated to characterize the fate of 2-ME and 2-MAA. 13C NMR spectroscopy was used to detect and assign metabolites in the urine of pregnant CD-1 mice following administration of 250 mg/kg of [1,2,methoxy-13C]-2-ME. Two-dimensional NMR methods were used to correlate signals from the labeled carbons in each 2-ME metabolite and to determine the number of hydrogens attached to each carbon. Structures were assigned from the NMR data together with calculated values of shift for biochemically feasible metabolites and by comparison to standards. Pathways involved in forming metabolites assigned in this study include transformation of 2-ME via ethylene glycol, conjugation with glucuronide or sulfate, and oxidation to 2-MAA. Additional metabolites were assigned that can be formed from further conversion of 2-MAA to glycine and glucuronide conjugates, as well as metabolites derived from the incorporation of 2-methoxyacetyl CoA derivatives into intermediary metabolism. Elucidation of the further metabolism of 2-MAA may be important for understanding the mechanisms by which 2-ME induces adverse effects.