Mutagenicity of N-nitrosodiethanolamine in the Salmonella/microsome test

Mutagenicity of a commercially available N-nitrosodiethanolamine (NDELA) and purified NDELA was examined, using Salmonella typhimurium TA100 as a tester strain. Purified NDELA was positive in the presence of liver activation system from either rats or hamsters, but the mutagenicity was completely lost when dimethyl sulfoxide (DMSO) was used as a solvent. In contrast, the commercial NDELA which was chemically of 93.8% purity showed positive mutagenicity without metabolic activation, and the liver activation system and DMSO had no effect on the direct mutagenic activity. These results indicate that an apparent discrepancy among previous findings of several investigators with the mutagenic response of NDELA might be due to an impurity in NDELA samples and the solvent, DMSO.