Some Metabolites of S-Pentyl-L-cysteine in the Rabbit and Other Species

Abstract

1. The metabolism of S-pentyl-L-cysteine has been investigated in the guinea pig, hamster, mouse, rabbit and rat and in vitro by liver slices of these animals and of the pigeon and by kidney slices of mouse, rabbit and rat.

2. The amounts of pentylmercapturic acid, 3-(pentylthio)lactic acid and 3-(pentylthio)pyruvic acid excreted have been measured.

3. All the species examined excreted pentylmercapturic acid, the amount varying from 2% of the dose by the guinea pig to 73% by the hamster. 3-(Pentylthio)pyruvic and 3-(pentylthio)lactic acids were not detected in the urine of the hamster or rat but were excreted by the other species in amounts approximately the same as those of pentylmercapturic acid.

4. ‘Hydroxypentylmercapturic’ acids were excreted by mouse, rabbit and rat and were identified in the case of the rabbit and rat.

5. 4-Carboxybutylmercapturic acid was identified in the urine of dosed mice, rabbits and rats. A further metabolite in rat urine was tentatively identified as 3-(4-carboxybutylthio)lactic acid.

6. Pentylmercapturic acid sulphoxide was detected in the urine of dosed guinea pigs and mice.

7. All tissue preparations examined converted pentyl-L-cysteine to pentylmercapturic acid. 3-(Pentylthio)lactic acid and 3-(pentylthio)pyruvic acid were formed by all tissues examined although only in trace amounts by hamster liver and rat kidney slices. All tissues examined formed hydroxymercapturic acids' although only traces were detected in digests containing hamster liver slices. 4-Carboxybutylmercapturic acid was formed in rabbit liver digests. With rabbit kidney a metabolite thought to be 3-(4-carboxybutylthio)lactic acid was produced.