Gas chromatographic-mass spectrometric analysis of stable isotopes of cysteine and glutathione in biological samples

A gas chromatographic-mass spectrometric (GC-MS) procedure for the determin ation of stable isotope labelled glutathione has been applied to animal and human samples. The method, based on preparation of the N,S-ethoxycarbonyl methyl eater derivative of the intact peptide, is rapid and requires little or minor tissue treatment. The same method was applied to cysteine. The me thod was found to be reliable in terms of within-day and between-day precis ion, accuracy and linearity. The procedure was applied in humans and animal s to determine in vivo the glutathione fractional synthesis rate using labe lled cysteine infusion, The glutathione fractional synthesis rate was found to be 22.5%/day in blood from a healthy volunteer and 337+/-29%/day in rat liver. (C) 1999 Elsevier Science BN. All rights reserved.