The second method of detecting LDH is based on the ability of LDH to catalyze the reverse reaction, i.e., oxidation of lactate to pyruvate using NAD+, which in turn is reduced to NADH. This reaction is coupled to another enzymatic reaction wherein NADH reduces INT ((2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride)) to a red formazan product that can be detected and spectrometrically quantitated between 450 to 490 nm. 34