Difficulties involved in diaminobenzidine histochemistry of endogenous peroxidase

Basically peroxidase (PO) histochemistry is used in different areas: haematologic physiopathology, estrogen-dependent genito-mammary physiopathology and immunoperoxidase histochemistry, both in electron microscopic cytochemistry and at the light microscopic level. In immunochemistry, endogenous peroxidatic activity is inhibited by means of various procedures. On the contrary, in haematology and in reproduction biology stainability of endogenous PO is mandatory; controls are achieved using different inhibitors. Literature data on the most appropriated technical conditions concerning fixation, processing and incubation, for PO staining are reviewed.