Significance of Measurement: Oxidized glutathione (GSSG) reflects the oxidative status of cells. The ratio of GSH to GSSG is a sensitive indicator of cellular redox balance and oxidative stress. Principle of Measurement: After masking reduced glutathione, GSSG is reduced to GSH by glutathione reductase and subsequently reacts with chromogenic reagents to generate a colored product. Absorbance at 412 nm is used to determine GSSG content.