Specificity of cytochemical procedures for localising peroxidase activity in the sarcoplasmic reticulum

Cytochemical evidence is reported for substantiating the view that when lightly-fixed skeletal muscle is incubated in a diaminobenzidine-H2O2 medium at pH 5, the resulting enhanced electron opacity of the sarcoplasmic reticulum is more likely to be due to a peroxidatic activity therein rather than to a non-enzymic binding reaction. The reticulum staining is absent in incubated sections of overfixed or boiled tissue; or if hydrogen peroxide is omitted from the incubation medium; or if aminotriazole is included in the medium.