The use of ferricyanide for the light and electron microscopic demonstration of succinic dehydrogenase activity.

Abstract

The conditions of the use of ferricyanide in the histochemical demonstration of succinic dehydrogenase activity (SDH) were investigated. The method is based on a simultaneous coupling reaction in which the ferrocyanide produced is captured by copper at the site of enzyme activity. The choice of an appropriate chelator to prevent the precipitation of copper by other components of the incubation medium was shown to be crucial. In the present study tartrate was found to give good results. The localization obtained is of high accuracy, no nonspecific attachment of the chemicals to tissue components could be detected. The highly electron dense final reaction product was found to cover the mitochondrial membranes as distinct granules of 40–80 A diameter separated by 30 A intervals. The side by side occurrence of mitochondria exhibiting normal, less, and no activity was confirmed in various tissues. The precipitate may be identified also in the light microscope owing to its dull brown colour, but for routine light microscopic purposes the precipitation of silver on its surface is recommended.