Fraction from human and rat liver which is inhibitory for proliferation of liver cells.

A comparative study was undertaken with human and rat liver of a fraction reported to have growth inhibitory activity when prepared from rat liver. Fractions which were soluble in 70% ethanol and insoluble in 87% ethanol were prepared from liver cytosols. Electrophoretic analysis under denaturing conditions indicated that there were several quantitative or qualitative differences in the fractions from the two species. Fractions from both human and rat liver were found to be inhibitory for the incorporation of 3H-thymidine into DNA of foetal chick hepatocytes. Under conditions in which the rat fraction inhibited precursor incorporation into DNA of rat liver epithelial cells there was not a significant inhibitory effect with the fraction from human liver. DNA synthesis in a rat hepatoma cell line was not significantly inhibited by preparations from either species. The data suggested that corresponding fractions from both rat and human liver could have inhibitory effects on precursor incorporation into DNA but the magnitude of the effects and target cell specificity may differ.