The influence of polycyclic hydrocarbons on the activity of NAD(P)H-dehydrogenating enzymes in rat thymus. A biochemical and histochemical study.

The action of benzo(a)pyrene, 3-methylcholanthrene and 7,12-dimethylbenzo(a)anthracene in the activity of the rat thymus D-T diaphorase (EC 1.6.99.2) and the NAD(P)H cytochrome C (EC 1.6.99.3) reductases of particulate fractions were studied in intact and adrenalectomized animals. These polycyclic hydrocarbons increased severalfold the activity of the D-T diaphorase in intact and adrenalectomized animals. The activities of the particulate enzymes were not affected by the carcinogens. Dicumarol suppresses the inducing effects of benzo(a)pyrene and adrenalectomy does not influence the inducing effects of benzo(a)pyrene and 3-methylcholanthrene. The histological distribution of the enzyme NAD(P)H-nitroblue tetrazolium reductase was studied and a marked increase in its activity in lymphocytes, macrophages and epithelial cells was found after the administration of the carcinogens.