Lack of specific inhibition of DNA repair in WI-38 human diploid fibroblasts by sodium saccharin.

The ability of sodium saccharin (NaS) to inhibit the repair of DNA damaged by UV irradiation was examined in cultured WI-38 human diploid fibroblasts. Cesium chloride density gradient ultracentrifugation was used to measure DNA repair and DNA replication. NaS (10-10,000 micrograms/ml) did not specifically inhibit UV light-induced DNA repair. At doses of NaS (1785 and 10,000 micrograms/ml) that caused a 62-67% inhibition of semiconservative DNA replication, there was little or no inhibition of DNA repair synthesis. In cell cultures not exposed to UV irradiation, NaS failed to induce DNA repair. RNA synthesis and protein synthesis were unaffected by NaS at all doses tested. The inhibition of semiconservative DNA replication at higher doses of NaS may be a manifestation of cytotoxicity. In contrast to results with NaS, WI-38 cells were very sensitive to DNA repair inhibition by the well-studied inhibitor quinacrine-HCl. These results do not support mechanisms of saccharin-induced tumorigenesis involving either direct induction of DNA damage or inhibition of the repair of DNA damage caused by other agents.