1. Sprague-Dawley rats were fed diets containing 0.06 per cent 3′-methyl-4-dimethylaminoazobenzine for 7 and 14 days. Different chemical constituents in the livers of these rats were studied by histochemical means.

  2. In the 7-day experimental animals, an increase of ribonucleic acid and a diminution of mitochondria and esterase began to appear in the periportal zone of the lobules, while a beginning depletion of glycogen was observed in the central vein area.

  3. In the livers of the 14-day experimental animals these changes became more evident and more consistent. An increase of alkaline phosphatase and a decrease of ribonucleic acid in the central vein area also became more obvious. The manifestations induced by ribonucleic acid were most consistent, and those induced by glycogen, esterase, mitochondria, and alkaline phosphatase were decreasingly so.

  4. The histochemically demonstrable succinic dehydrogenase, acid phosphatase, and neutral fat seemed only slightly affected.

  5. All the changes were strikingly lobular in pattern and were observed before bile duct proliferation and significant morphological changes could be detected.

*

This investigation was supported by grants C-1913, from the National Cancer Institute, U.S. Public Health Service; P-26, from the American Cancer Society; and by funds from the Robert Welch Foundation.

A preliminary report of this work was presented before the Annual Meeting of the American Association for Cancer Research, Chicago, 1957 (Proc. Am. Assoc. Cancer Research, 2:192, 1957).

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