[Kinetics of (C14) thymidine metabolism in hepatomas and tissues from normal and tumor-bearing animals].

The incorporation of 14C-thymidine into DNA and the acid-soluble fraction of mouse hepatomas 22A and 48 and into DNA of rat Zajdela hepatoma as well as into corresponding fractions of liver, spleen and thymus of normal organisms and tumor-bearing animals, was studied. Ion exchange chromatography on DEAE-cellulose disks was used to study distribution of the 14C-thymidine label between nucleosides, nucleotides, and nucleoside di- and triphosphates of the cell pool. The distribution of the label as early as 5 to 10 minutes after administration of 14C-thymidine was found to be specific for each tissue studied and remains unchanged for at least 1 hour. Specific radioactivity (per mg DNA) of the acid-soluble fraction in 22A hepatoma is declined from the original high level very rapidly from the first minutes following administration of labelled thymidine with a corresponding increase in the specific radioactivity of DNA. The character of the both curves depends on the growth rate of hepatomas studied. Systemic effect of the highly malignant hepatomas manifests itself in their successful competition with the host's tissues for the vital precursor--thymidine. This phenomenon entails a drastic suppression of the incorporation of thymidine into the immunocompetent host's organs--spleen of mice and thymus of rats.