Abstract
1. Histochemical procedures have been developed for the demonstration of reduced pyridine nucleotide dependent systems metabolizing 3, 4-benzypyrene, perylene, 9,10-dimethyl-1,2-benzanthracene and 1, 2-benzanthracene.
2. For these procedures, an in situ indicator technique has been employed in which alterations of the fluorescence of the substrates coated on tissue sections is used to demonstrate the sites of enzyme activity.
3. Positive reactions have been found in the hepatic cells of rat, mouse, hamster, monkey, and man. The cells of the central portion of the hepatic lobule are more active than those of the periphery in all species.
4. A survey of rat tissues has shown positive reactions also in the distal portion of the proximal convoluted tubules of the kidney, the zona fasciculata and zona reticularis of the adrenal, the interstitial cells of the testis, the follicular epithelium of the thyroid and the alveolar walls of the lung.
5. The activity is considerably higher in sections of liver, kidney, thyroid, testis, and lung from rats injected with methylcholanthrene than in control animals; in the adrenal, no such increase is found.