A method for determination of total glutathione and total cysteine as S-carboxymethyl derivatives by using an amino acid analyzer, and its application to samples from rat liver, kidney and blood after intraperitoneal administration of 2-(4-carboxy-D-gluco-tetrahydroxybutyl)thiazolidine-4-carboxylic acid.

The effects of intraperitoneal administration of 2-(4-carboxy-D-gluco-tetrahydroxybutyl)thiazolidine-4-carboxylic acid (CGUA), a cysteine derivative conjugated with glucuronic acid, on total glutathione and total cysteine contents in rat tissues were investigated. Total glutathione (GSH and GSSG) and total cysteine (cysteine and cystine) were determined by a new method consisting of preparation of S-carboxymethylglutathione (CMSG) and S-carboxymethylcysteine (CMC), respectively, and subsequent analyses with an amino acid analyzer. CGUA was determined by a coloration method employing an acidic ninhydrin reagent. Total cysteine contents in liver, kidney and plasma rapidly increased to 2.3, 2.7 and 6.5 times the levels of the controls, respectively, after CGUA administration at a dose of 5 mmol/kg of body weight. Total glutathione content did not change significantly in the liver or blood except for the kidney with a significant increase during the first 1-h period after administration. CGUA content increased markedly in these tissues, especially in the kidney, and 30% of administered CGUA was excreted in urine within 2h. These results indicate that CGUA is converted into cysteine in vivo, suggesting the usefulness of this compound for protection of the kidney and the liver.