An automated colorimetric method for the estimation of lactate dehydrogenase activity in serum.

An automated method for estimating lactate dehydrogenase (LDH) in serum is presented. Fe3+ is reduced to Fez+ by NADH formed when lactate is oxidized to pyruvate. Fe2+ complexed with 2,2-bipyridyl is measured colorimetrically. Solutions of Fe2+ salt are used as standards. Nicotinamide is used to stabilize NAD+ in solution and is shown to enhance enzyme activity. The method is less expensive than most automated methods published and reagents are stable for at least 4 weeks. Results correlate well with a kinetic spectrophotometric method.