CHEMICAL QUANTIFICATION OF UNSCHEDULED DNA-SYNTHESIS IN CULTURED-HEPATOCYTES AS AN ASSAY FOR THE RAPID SCREENING OF POTENTIAL CHEMICAL CARCINOGENS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (8) , 3010-3015
Abstract
Technical modifications of the quantitative determination of unscheduled DNA synthesis in cultured [rat] hepatocytes are described which allow for the rapid identification of potentially carcinogenic chemicals on a large-scale screening basis. The test is based on the biochemical quantification of [methyl-3H]thymidine incorporation into DNA in the presence of hydroxyurea following isolation of nuclei from hepatocytes treated with the agent under study. This procedure (nuclei procedure) eliminates most of the background radioactivity which otherwise obscures the stimulation of DNA repair synthesis by agents that induce a relatively weak response. By combining the nuclei procedure with a double-labeling technique, test results can be obtained within a few hours after exposure of hepatocytes to the test agents. A test series involving 41 agents confirmed the reliability of the nuclei procedure for the assay of DNA repair synthesis. Chemicals which had yielded conflicting results previously in the autoradiographic hepatocyte DNA repair test, such as 4-acetylaminofluorene, or which had passed unrecognized in previous in vitro tests, such as the potent liver carcinogen methapyrilene hydrochloride, scored clearly positive in this test protocol.