Analytical methods for the study of urinary thioether metabolites in the rat and guinea pig

Methods are described for the isolation and identification of three classes of bivalent sulfur metabolites characterized as neutral methylthio ethers, ethyl acetate-soluble acidic thioethers and ethyl acetate-insoluble acidic thioethers from rat and guinea pig urine. After extraction of the metabolites by the ammonium carbonate-ethyl acetate procedure, the individual metabolites are separated by capillary gas chromatography and/or by high-performance liquid chromatography with both mu Bondapak C18 and Porasil columns. Identification of the metabolites is based on gas chromatography-mass spectrometry (electron impact) and on fast atom bombardment mass spectrometry. Interesting species differences in metabolism were observed. The major ethyl acetate-soluble acidic thioethers in rat urine are mercapturic acids. In contrast, in the guinea pig a new pathway involving mercaptopyruvic, mercaptolactic and mercaptoacetic acids is operative. The thioether metabolites of styrene oxide and phenanthrene are described, but the procedures have been applied in studies of several drugs and environmental chemicals in our laboratory.