[Benzidine and its derivatives in the immunohistochemical analysis of peroxidase]

Authors have studied the application of benzidine and its derivatives for the demonstration of the marker enzyme horseradish peroxidase. Benzidine compounds are known to be in a blueish dimeric form under oxidative circumstances, while after polymerization they yield a dark brown end product. If the dimeric state is stabilized, the 3,3'-dimethoxy benzidine (o-dianisidin) appears to be the most suitable to demonstrate peroxidase. The o-dianisidin reaction has the advantage of high sensitivity and that the end product shows a birefringence in polarized light. Upon mounting with organic media the end product is stable.