Nothing dehydrogenase reaction as an artefact in serum isoenzyme analyses.

A nonspecific staining occurs in serum in isoenzyme methods based on tetrazolium staining reactions. The artefact is pronounced when a large application volume, a prolonged incubation time, distinctly alkaline conditions, or excess of phenazine methosulphate is used. Only phenazine methosulphate and a tetrazolium stain are required for the appearance. Inhibition studies and histochemical staining reactions give evidence that protein-bound sulphydryl groups are responsible for the artefact in serum.