[A novel fluorophotometric method for assaying free glutathione of both reduced and oxidized in plasma]

To investigate the measurement of free glutathione of both reduced or oxidized (i.e. GSH and GSSG) in plasma, and to evaluate the redox state of GGSH/GSSG in human plasma, both GSH and GSSG in plasma were measured by fluorophotometry based on the facts that one molar GSSG can be reduced to two molar GSH by dithiothreitol(DTT) under the condition of the pH being about 6.0, and GSH can provide both primary amine and thiol groups to react with the two carbonyl groups of O-phthaldehyde (OPA) to form a fluorescent ternary isoindole complex at pH 8.0. This method can at least measure 16 picomole GSH and 8 picomole GSSG respectively in the tube. The variation coefficient (CV) for intra-ssay and intera-ssay is about 4. 6% and 3.9% for GSH and 3.5% and 4.1% for GSSG respectively. The recovery of GSH and GSSG added to the plasma is (99.77% +/- 5.70)% and (99.28% +/- 4.73)% respectively. The concentration of GSH and GSSG in the plasma of young healthy volunteer is (16.5 +/- 2.4) nmol x mL(-1) and (1.7 +/- 0.35)nmol x mL(-1) respectively, without significant difference between male and female. This measurement method is simple with great sensitivity and selectivity for rapid measuring GSH and GSSG in human plasma simultaneously.