New methods for the histochemical and cytochemical demonstrtion of cytochrome c oxidase and of cytochrome c- cytochrome oxidase system

New histochemical and cytochemical methods for the demonstration of cytochrome c oxidase and of cytochrome c-cytochrome oxidase system are described, using neotetrazolium chloride in the presence of p phenylenediamine with or without additional cytochrome c. These enable the cytochemical visualization of the sites of enzyme activity at the intracellular level in fresh cell suspensions and in fresh tissue blocks under aerobic conditions, and permit the histochemical visualization of the distribution of the enzyme activity in various tissues in frozen tissue sections. The colorimetric estimation of the enzyme activity is also possible in the combination of the methods previously described.