Glutathione is an intracellular, nonprotein thiol that appears to play an important role in protection of the cell against cytotoxic drugs (1 ) and has been implicated in the control of cell cycling (2 ,3 ) and apoptosis (4 ,5 ). It can exist in an oxidized (disulfide, [GSSG]) and a reduced (sulphydryl, [GSH]) form. In general, GSSG comprises less than 1% of the total intracellular glutathione. In circumstances of oxidative stress, GSH dimerizes to form glutathione disulfide (GSSG), making protons available to neutralize reactive oxygen species (Reaction 1). In vivo, reduction of GSSG is catalysed by glutathione reductase, efficiently regenerating high intracellular GSH levels (Reaction 2)
