Abstract
Metabolism of N-(2-mercapto-2-methylpropanoyl)-L-cysteine (SA96), a dithiol compound developed as an anti-rheumatic, was studied in rats and dogs by quantitative determination of SA96 and some metabolites in the blood and urine, by using gas chromatographic and high performance liquid chromatographic techniques. 1) In both dogs and rats, when administering SA96 orally, SA96 and its metabolites appeared in the blood within 30 min, indicating rapid absorption of SA96 through the digestive tract. N-[2-Methyl-2-(methylthio) propanoyl]-L-cysteine (SA679), S-methyl-N-[2-methyl-2-(methylthio) propanoyl]-L-cysteine (SA672) and (4R)-7, 7-dimethyl-6-oxo-tetrahydro-3H-1, 2, 5-dithiazepine-4-carboxylic acid (SA981) were found in both species as metabolites in the blood and urine. 2) In both species, approximately 40% of the dose was recovered in the urine as unchanged SA96, SA679, SA672, SA981 and unknown disulfides within 24 h after oral administration. 3) There was found a species difference in the ratio of these metabolites. In rats, SA679 was the principal metabolite in both the blood and urine, while, in dogs, SA981 was the principal metabolite in the blood and unknown disulfides of SA96 in the urine.
