Validation of enhanced Ames assay using N-nitrosamine positive controls

UKEMS 2024 -- Enhanced testing conditions for the Bacterial Reverse Mutation (Ames) assay, using 30% rat or hamster liver S-9 mix, are recommended due to the reported reduced assay sensitivity under standard assay conditions for some N-nitrosamines. The current guidance requires the inclusion of two concurrent N-nitrosamine positive controls to confirm the suitability of the enhanced Ames test for N-nitrosamines. The objective of this study was to assess the mutagenicity of two N-nitrosamines, N-nitrosodiethylamine (NDEA) and Methyl(nitroso)(2-phenylethyl)amine (MNPA) using 5 bacterial strains (Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and E.coli strain WP2 uvrA pKM101) following pre-incubation methodology (30 minutes).