1. Normal albino rats, rats fed diets containing the carcinogenic azo dye 3′-methyl-4-dimethyl-aminoazobenzene, and rats with liver tumors were given intraperitoneal injections of solutions containing adenine-8-C14. Animals were sacrificed from each group at 3 hours, 24 hours, and 7 days following the administration of the isotope, and the liver and tumors were fractionated into acid-soluble, total nucleic acid, DNA and nuclear RNA fractions. C14 activity and phosphorus were determined on all fractions.

  2. The incorporation of the isotope by DNA was greatest in the tumor tissue, intermediate in the liver from the dye-fed animals, and least in the normal liver. The concentration of isotope for each tissue increased at each time interval following the administration of the labeled adenine.

  3. The isotope was incorporated into the nuclear RNA at a greater rate than into the other nucleic acid fractions. This was especially true for the tumor tissue; however, there was also considerable activity in this fraction obtained from the livers of the normal and the dye-fed animals. At subsequent periods following the administration of the labeled adenine, the activity of this nuclear RNA decreased while the DNA and the cytoplasmic RNA were increasing.

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This study was aided by a grant from the American Cancer Society on recommendation of the Committee on Growth of the National Research Council.

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