Studies on the intracellular composition of liver and liver tumor from rats fed 4-dimethylaminoazobenzene.

In a previous study (8) the livers of rats fed the hepatic carcinogen, 4-dimethylaminoazobenzene, were separated by differential centrifugation into the nuclei, large granules (mitochondria), small granules (microsomes), and a supernatant fluid (particles nonsedimentable at 19,000 X g). Anal yses for protein, nucleic acids, riboflavin, and pro tein-bound aminoazo dye were made on each frac tion. The ingestion of the dye in a diet low in ribo flavin increased the protein and desoxypentosenucleic acid content of the nuclear fraction. In diets containing either low or high levels of riboflavin, 4-dimethylaminoazobenzene reduced the ribo flavin content of the large granules and superna tant fluid, lowered the level of protein in the large granules, and decreased the pentosenucleic acid content of the large and small granules. Proteinbound dye was found in all the fractions, with the highest concentrations occurring in the small gran ules and supernatant fluid. The protein-bound dyes appear to have causal significance in the carcinogenic process induced by 4-dimethylaminoazobenzene (6). Since the level of protein-bound dye in the liver reaches a maxi mum at 4 weeks and thereafter decreases (6), the above studies were made on rats fed the dye for this length of time. However, hepatic neoplasms do not occur until the dye has been fed for several months beyond this maximum. Therefore, it was of interest to compare the intracellular composi tion of the liver in rats fed the dye for 4 to 5 months and the tumors arising in such livers.