An Automated Colorimetric Method for the Estimation of Lactate Dehydrogenase Activity in Serum

Abstract

An automated method for estimating lactate dehydrogenase (LDH) in serum is presented. Fe³⁺ is reduced to Fe²⁺ 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 spectro-photometric method.