Macroscopic enzyme histochemistry in myocardial infarction: artefactual nature of the creatine phosphokinase reaction.

The histochemical creatine phosphokinase (CPK) tetrazolium test has been evaluated to detect recent human myocardial infarction in gross slices of the heart at necropsy. The demonstration of the lesion with this method has been assumed to result from local loss of CPK from the damaged myocardium. However, the present study indicates that the mechanism involved depends on localising NADPH tetrazolium reductase and not CPK. Phenazine methosulphate (PMS), when added to the incubating medium as an electron-acceptor to circumvent the tetrazolium-reductase (diaphorase) system, resulted in generalised false staining of the heart slice.