FULLY AUTOMATED-ASSAY FOR TOTAL HOMOCYSTEINE, CYSTEINE, CYSTEINYLGLYCINE, GLUTATHIONE, CYSTEAMINE, AND 2-MERCAPTOPROPIONYLGLYCINE IN PLASMAAND URINE

We describe a 6-min HPLC method to measure the total concentrations of the most important thiols in plasma and urine-cysteine, homocysteine, cysteinylglycine, and glutathione-as well as the concentrations in pl asma and urine, respectively, of cysteamine and 2-mercaptopropionylgly cine, two compounds used to treat disorders of cysteine metabolism. Pr ecolumn derivatization with bromobimane and reversed-phase HPLC were p erformed automatically by a sample processor. Throughput was up to 100 samples in 24 h. The within-run CV ranged from 0.9% to 3.4% and the b etween-run CV ranged from 1.5% to 6.1%. Analytical recovery was 97-107 %, with little difference between plasma and urine samples. The detect ion limit was similar to 50 nmol/L for all the analytes studied. Thiol concentrations were determined in the plasma of 206 healthy donors an d in the urine of 318 healthy donors distributed for age and sex. Mean values of plasma cysteine and homocysteine were significantly lower i n infants (ages, <1 y) compared with other age groups (P <0.005). In a dults, mean plasma homocysteine values were higher in males than in fe males (9.2 vs 6.7 mu mol/L, P <0.0001) and in the 6- to 10-year-old gr oup (P <0.05). Mean values for glutathione and cysteinylglycine were n ot sex-and age-dependent. In urine, both cysteine and homocysteine sho wed a wide range of variation.