CYTOCHEMICAL DEMONSTRATION OF SUCCINIC DEHYDROGENASE BY THE USE OF A NEW p-NITROPHENYL SUBSTITUTED DITETRAZOLE

1. A new p-nitrophenyl substituted ditetrazole, 2,2'-di-p-nitrophenyl-5,5'-diphenyl-3,3'-(3,3'-dimethoxy-4,4'-biphenylene) ditetrazolium chloride (Nitro-BT), is introduced, which possesses most of the properties of an ideal reagent for histochemical purposes. It permits the cytochemical visualization of the sites of enzymic activity in tissue sections from 2-8 µ thick, under aerobic conditions, after a relatively short incubation period. 2. A comparison was made of the various tetrazoles in common use with several new p-nitro substituted analogues of these agents. 3. A survey was presented of the enzyme distribution in the major tissues of the rat and dog. Evidence for the reliability of cytochemical localization is provided by illustrative material in selected tissues. 4. The new tetrazole can be employed for the diphosphopyridine nucleotide and triphosphopyridine nucleotide diaphorase systems as well as for the succinic dehydrogenase system by substituting Nitro-BT for blue tetrazolium (BT) in the incubation media.