NAD(P)H-dependent cellular oxidoreductase enzymes in viable cells can reduce the tetrazolium dye MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to its insoluble formazan, which has a purple color. The quantity of formazan is measured by recording changes in absorbance at 570nm using a spectrophotometer. Under defined conditions, it can reflect the number of viable cells present. MTT assays can be used to measure cytotoxicity (loss of viable cells) or cytostatic activity (shift from proliferation to quiescence) of potential medicinal agents and toxic materials.
