Bioluminescent flow sensors: L-lactate dehydrogenase activity determination in serum

The catalytic activity of serum L-lactate dehydrogenase (LDH), was determined by monitoring the NADH produced by LDH with bacterial bioluminescent enzymes immobilized on a nylon coil. The LDH reaction of L-lactate with NAD took place in a flow-through mixing coil that preceded the bioluminescent detector coil. The response was linear from 1 to 5000 U/l at 37 degrees C and from 3 to 2000 U/l at 25 degrees C. The intra- and inter-assay reproducibility (CV%) were less than 10% and recovery range was 92% to 110%. The results agreed well with those obtained with a spectrophotometric method.