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.