Metabolism of N-nitroso-1,3-thiazolidine in the rat

[2-14C]N-nitroso-1,3-thiazolidine (125 mg/kg body weight) administered by gavage to rats was excreted mostly (81% of the dose) in the urine with a smaller amount (7%) in respired air. The major metabolite in the urine (77.2%) was 2-hydroxy-1,3-thiazolidine and minor quantities of the isomers 4- and 5-hydroxy-1,3-thiazolidine were also detected. The presence of hydroxy-1,3-thiazolidine, determined using mass spectrometry and high-performance liquid chromatography, indicated that alpha-hydroxylation and denitrosation are major metabolic pathways of N-nitroso-1,3-thiazolidine. Analysis of the non-acidic urine extract with gas chromatography-mass spectrometry (GC-MS) using untreated on-column injection and heated split injection gave differing results. Compounds detected using the latter technique may have been artefacts formed by pyrolysis in the heated injection port. Analysis of the metabolites by direct probe mass spectrometry (unheated) and Fourier transform infra-red spectroscopy supported the results seen with on-column GC-MS.