An automated fluorometric method for determination of malate dehydrogenase activity in serum.

An automated system for the sensitive, reproducible determination of malate dehydrogenase activity in serum is described and evaluated. After incubation of serum at 25#{176}C and double dialysis, fluorometry is used to measure the disappearance of NADH during reaction. Certain precautions are necessary to maintain the stability of NADH and oxaloacetate and to assure washout of adsorbed serum components from the system. Control serum (Enza-trol) is used as an enzyme reference material. Results from the automated method agree well with those from an independent manual method. Replicability is excellent, and results from samples stored at 4#{176} or -20#{176}C are essentially the same as those from fresh samples. A mean value of 36.6± 8.5 U of malatedehydrogenase per literwas obtained on sera from 34 healthy adults, a value that agrees well with normal values obtained by others.