Cytochemical discrimination between catalases and peroxidases using diaminobenzidine

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Abstract
The influence on diaminobenzidine staining of four variables: prefixation in aldehyde, temperature and pH of incubation, and H2O2 concentration, was investigated in catalase-, as well as in peroxydase-containing material. Catalase from five different sources and five types of peroxidase were examine. It is conclude: (a) when cells are incubated without prior fixation, in a DAB medium at room temperature and pH 7.3 with 0.003% H2O2, peroxidases produce a visible cytochemical stain, while catalases do not; (b) the cytochemical reaction elicited by catalases is stimulated by prior aldehyde fixation in specified conditions, and incubation at 45° C and pH 9.7 with 0.06% H2O2; (c) under the latter circumstances several peroxidases also stain. Ultrastructural preservation is satisfactory in tissues incubated prior toxation.