NITRITE-INDUCED MUTATIONS IN A FORWARD MUTATION ASSAY - INFLUENCE OF NITRITE CONCENTRATION AND PH

The mutagenicity of sodium nitrite at three pHs (7.4, 6.4 and 5.4) has been investigated by treating a shuttle vector plasmid in vitro and a ssaying for mutations within the supF target gene following replicatio n of the damaged plasmid in human Ad293 cells. Mutation frequency incr eased with increasing nitrite concentration and decreasing pH. Among t reatments from which a significant number of mutants could be collecte d, the most commonly induced mutations were GC --> AT transitions (44- 56% of total mutations), followed by GC --> TA transversions (24-30%). The types of mutations induced at different nitrite concentrations an d different pH's were similar, though some differences in their distri bution throughout the supF gene were noted. These results provide info rmation on the types of mutations that may be produced following the p rocessing of nitrite-induced DNA damage in human cells.