Stabilization of glutathione in urine and plasma: Relevance to urinary metal excretion studies

The present studies demonstrate the instability of glutathione (GS) in urine and plasma and illustrate the importance of developing procedures to stabilize GS in biological fluids. The rapid loss of urinary GSH was not prevented by inhibition of γ-glutamyltranspeptidas (γ-GTP) with L-(αS,5S)-α-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125), by EDTA, or by sodium citrate. GS in urine could be stabilized for extended periods of time by acidification of samples immediately after collection. In order to accurately measure urine and plasma GS concentrations, samples were analyzed by a known additions technique. The relevance of these analytical procedures to metal excretion studies is discussed.