DNA-SYNTHESIS INHIBITION AND REPAIR DNA-SYNTHESIS IN CHO ADE(-) C-CELLS - AN ALTERNATIVE APPROACH TO GENOTOXICITY TESTING

We describe an alternative assay to determine genotoxicity. Its main f eature is that it combines two measures in a single experiment; the in hibition of replicative DNA synthesis together with the stimulation of DNA repair. We show that, in tests of four different genotoxic agents , the assay gives results that are entirely consistent with what is kn own about the mode of action of these agents. In addition, we have dem onstrated that chemical carcinogens requiring metabolic activation can be examined using a standard procedure of incubation with a microsoma l activating fraction. We consider the combined assay for DNA synthesi s inhibition and repair synthesis to be a useful way for the rapid pre screening of chemicals suspected of genotoxic activity on the level of mammalian cells.