Glutathione is the principal intracellular low-molecular-weight thiol that plays a critical role in the cellular defense against oxidative and nitrosative stress in mammalian cells. Diminished glutathione levels have been observed in the early stages of apoptosis. BioVision’s ApoGSH™ Glutathione Detection Kit provides a simple in vitro assay for detection of total glutathione changes in apoptosis and other samples. The assay utilizes monochlorobimane (MCB), a dye that appears to form an adduct exclusively with glutathione. The unbound MCB is almost nonfluorescent, whereas the dye fluoresces blue (Ex./Em. = 380nm/461nm) when bound to glutathione of reduced or oxidized form. The reaction is catalyzed by glutathione S-transferase. Thus, the amount of total glutathione can be easily detected using a fluorometer or a 96-well fluorometric plate reader.