Propachlor detoxication in the small intestine: cysteine conjugation.

14C-labeled 2-(S-cysteinyl)-N-isopropylacetanilide was recovered from the media of everted sacs of rat small intestine incubated in media that contained [14C] propachlor (2-chloro-N-isopropyl-[1(-14) C]acetanilide). The metabolite was identified on the basis of chromatographic characteristics and mass spectra of the butyl ester-trifluoro-acetamide derivative. This evidence shows that the cysteinyl conjugate was formed during incubations of the small intestine. Although the glutathione conjugate has not been isolated from the intestine, it is a likely precursor of the cysteinyl metabolite. Data from experiments conducted with 10(-5) and 10(-4) M propachlor in the media showed that the capacity to metabolize propachlor to polar metabolites was approximately the same throughout the length of the small intestine.