Bureau of Standards.

The pyruvate-to-lactate assay for determining lactate dehydrogenase (EC 1.1.1.27) can now yield linearity equal to or better than that obtained by the lactate-to-pyruvate assay. In addition, there are significant advantages to the pyruvate-to-lactate reaction: (a) a greater change in ab-sorbance per unit time, which allows more accurate spectrophotometric readout; (b) lower reactant concen-trations are required, which substantially reduces the cost per assay; (c) solid reagents are used to prepare the assay solution; and ( reagent solutions are more stable. How-ever, impurities present in commercial NADH preparations may substantially affect measured lactate dehydrogenas