Biochemical and quantitative histochemical study of reduced pyridine nucleotide dehydrogenation by human colonic carcinomas.

This study shows a marked increase in the activity of the soluble enzyme DT-diaphorase and of the histochemical activity of the reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate nitroblue tetrazolium menadione-mediated reductases in human colonic carcinomas when compared with the enzymatic activities of portions of the colon uninvolved by the carcinomatous process. The activity of the reductases in histological sections was quantitated with a microphotometer. It is believed that the increase in histochemical nitroblue-tetrazolium reductase activity in the histochemical reactions in colonic carcinomas is a real reflection of the activity of the DT-diaphorase, because the increase in the dehydrogenation of reduced nicotinamide adenine dinucleotide equals the dehydrogenation of reduced nicotinamide adenine dinucleotide phosphate when measured biochemically in the soluble fraction, or histochemically, by microspectophotometry in tissue sections; meanwhile, the biochemical dehydrogenation of NAD(P)H by the particulate fractions shows that the enzymatic activities are not altered by the neoplastic process. The biological significance of these changes is discussed in the text.