Glutathione and gamma-glutamylcysteine in whole blood, plasma and erythrocytes.

A method for the simultaneous determination of glutathione and gamma-glutamylcysteine in capillary blood samples is described. The whole blood levels of glutathione and gamma-glutamylcysteine are t.09 +/- 0.20 mmol/l and 25 +/- 8 mumol/l (M +/- S.D.), respectively. The plasma concentration is approximately 4 mumol/l for both compounds. It is important to treat the blood samples with a reducing agent before protein precipitation to release glutathione and gamma-glutamylcysteine from disulfide linkages since, otherwise, 30--40% of the glutathione and 80% of the gamma-glutamylcysteine is lost with the protein precipitate. Whole blood is preferable to washed erythrocytes for the analysis since the washing procedure involves losses of, especially, gamma-glutamylcysteine.