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Studies on the Intracellular Composition of Livers from Rats Fed Various Aminoazo Dyes

II. 3'-Methyl-, 2'-Methyl-, and 2-Methyl-4-dimethylaminoazobenzene, 3-Methyl-4-monomethylaminoazobenzene, and 4'-Fluoro-4-dimethylaminoazobenzene

J. M. Price, Ph.D., E. C. Miller, Ph.D., J. A. Miller, Ph.D. and G. M. Weber, B.S.

(From the McArdle Memorial Laboratory, Medical School, University of Wisconsin, Madison 6, Wisconsin)

1. The livers of rats fed either no azo dye or equimolar levels of 2'-, 3'-, or 2-methyl-4-dimethylaminoazobenzene, 3-methyl-4-monomethylaminoazobenzene, or 4'-fluoro-4-dimethylaminoazobenzene for 4 weeks were perfused, homogenized, and separated by differential centrifugation into nuclear, large granule, small granule, and supernatant fluid fractions. The original homogenate and the fractions were analyzed for protein, nucleic acids, riboflavin, and protein-bound aminoazo dye. The results obtained were compared with previous data on the livers of rats fed other aminoazo dyes and on the tumors induced by 4-dimethylaminoazobenzene.

2. From these data it appears that the ingestion of 4-dimethylaminoazobenzene and its C-monomethyl derivatives caused increases in the amounts of protein and desoxypentosenucleic acid in the nuclear fraction; decreases in the amounts of protein, pentosenucleic acid, and riboflavin in the large granule fraction; and increases in the pentosenucleic acid content of the supernatant fluid fraction, which were roughly proportional to the carcinogenicities of the dyes fed. The weak carcinogen 3-methyl-4-monomethylaminoazobenzene was an exception in that it caused a significant reduction in the riboflavin content of the large granules. The changes caused by the strong carcinogen 3'-methyl-4-dimethylaminoazobenzene were not altered by raising the level of dietary casein from 12 to 24 per cent. 4'-Fluoro-4-dimethylaminoazobenzene did not fit into this series, since it failed to cause as great changes as would be expected from its high activity.

3. 2-Methyl-4-dimethylaminoazobenzene differed from the other dyes in that it caused an increase above normal in the number and total mass of the large granules; this fraction contained considerably more protein and riboflavin and less pentosenucleic acid than normal.

4. Ingestion of any of these dyes gave rise to protein-bound aminoazo dye in each fraction of the liver cell; the highest concentration and greatest fraction of the total were always found in the supernatant fluid.

5. Histological studies suggested that the alterations in the composition of the large granule fractions after ingestion of the dyes were due chiefly to changes in the numbers of large granules in the parenchymal liver cells, while proliferation of the bile duct-like cells may have been responsible for the alterations in the composition of the nuclear fraction. The increase in the amount of nuclear desoxypentosenucleic acid which occurred when highly carcinogenic dyes were fed was largely the result of an increase in the number of nuclei per unit weight of tissue.

Predoctoral Research Fellow, U.S. Public Health Service, 1948–49.

Received 8/ 9/49.

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