Water-Soluble Metabolites of Carbaryl (I-Naphthyl N-Methylcarbamate) in Mouse Liver Preparations and in the Rat

Abstract

The biliary and urinary metabolites of carbaryl, I-naphthyl N-methylcarbamate, were examined in the rat using 1-[1-14C]naphthyl N-methylcarbamate and I-naphthyl N-methyl-[14C]carbamate. Metabolites formed by incubation of 1-[14C]naphthyl N-methylcarbamate with supernatant from the centrifugation at 10,000 g of mouse liver homogenate were also examined. In each case substantial amounts of water�soluble materials present were identified as thioether amino acid conjugates. After acid treatment these conjugates had chromatographic properties consistent with their identification as S-(4-hydroxy-l-naphthyl)cysteine and S-(5-hydroxy-l-naphthyl)cysteine. Quantitative determination allowed assignment of up to 55, 15, and 24% of the metabolites in bile, urine, and liver preparations respectively as compounds affording the cysteines on acid treatment. Some acid-labile conjugates of urine and bile were estimated indirectly by reverse isotope-dilution analyses.