The MTS reagent is a tetrazolium compound that is reduced by dehydrogenase enzymes found in metabolically active cells. This reduction process occurs in the mitochondria, producing a soluble formazan dye. The amount of formazan produced is directly proportional to the number of living cells. The absorbance of the formazan dye can be measured using a spectrophotometer at 490 nm, providing a quantitative measure of cell viability.
