NATURE OF INHIBITORS OF DNA SYNTHESIS IN RAT-LIVER HEPATOMA CELLS

1. 1. Inhibition of DNA synthesis by the cell sap from ascites hepatoma cells of rat liver has been shown to be due to two factors acting synergistically. One factor (Fraction I) which was rather thermostable seemed to be arginase. Another, thermolabile, factor (Fraction II) has been separated by CM-cellulose chromatography, but its nature has not yet been clarified. 2. 2. The above two factors were found to be present in adult rat-liver cell sap. In regenerating liver cell sap, Fraction II seemed to be relatively increased and in the liver cell sap from fetal or newly born rats Fraction II became a primary inhibitor. 3. 3. In hepatomas, both factors tended to be decreased depending on the malignancy. 4. 4. Rat-liver cell sap could inhibit DNA synthesis in 3′-methyl-4-dimethylaminoazobenzene-induced primary hepatoma slices, but the DNA synthesis in 24-h regenerating liver slices seemed to be resistant to inhibition by liver cell sap. © 1969.