SECTION VI. DESHYDROGÉNASES ET TRANSFERTS D'HYDROGENE 



ELECTRON TRANSPORT ENZYMES: 



BIOCHEMICAL ASSAYS 



AND TETRAZOLIUM STAINING STUDIES 



A. B. NOVIKOFF 



Albert Einstein Collège of Medicine, Yeshiva University, New York 



The difficulties in localizing the intracellular sites of dehydrogenase 

 activities by the tetrazolium technique will be indicated. Lactic dehydro- 

 genase (LDH) will be used to illustrate the spécial problems of soluble | 

 dehydro gênas es. The distribution of LDH activity among subcellular } 

 fractions isolated from rat liver and ascites tumor (Novikoff hepatoma) ; 

 will be compared with the distributions of lactate-tetrazolium reductase, 

 DPNH-tetrazolium reductase, DPNH-dichlorophenolindophenol reductase, 

 and DPNH-cytochrome c reductase activities. It will be suggested that 

 the term **diaphorase*' be abandoned in cytochemistry. 



The advantages will be outlined of using formal-calcium-fixed tissues 

 and reduced coenzymes (DPNH and TPNH) as substrates in the tetrazolium 

 procédure. The results obtained with this technique in a wide variety of 

 tissues will be presented to indicate: (1) that neither DPNH nor TPNH 

 can be used in the tetrazolium procédure to stain either mitochondria 

 or "microsomes" generally; and (2) that the tetrazolium technique may 

 be of great value in indicating cells in which TPN-linked metabolic 

 séquences may be of spécial significance, such as in a variety of endo- 

 crine tissues (adrenal, pancréas, pituitary, thyroid) and in the macula 

 densa, thin limbs of Henle's loops, and collecting ducts in the papilla 

 (rat kidney). 



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