The effects of S9 mix from rat oesophagus, salivary gland, and liver on the mutagenicity of the rat oesophageal carcinogen N-nitroso-N-methylaniline in the Salmonella typhimurium assay.

The present study examines the feasibility of using the Salmonella typhimurium plate-incorporation assay of Ames for detecting target-organ specificity with N-nitroso-N-methylaniline (NMA), a compound for which the target site for tumour formation in the rat is the oesophagus. Thus it was anticipated that the oesophagus would bioactivate this compound. The compound has been investigated using S9 from Aroclor- and NMA-induced rat oesophagus, salivary gland and liver in the presence and absence of the co-mutagen, norharman. No response to NMA was seen with oesophageal S9 even though benzo[a]pyrene produced a dose-related increase in revertants in strain TA98 and TA100. No response to NMA was seen with salivary-gland S9. However, a response was produced with Aroclor-induced rat-liver S9 in the presence of norharman and with NMA-induced rat-liver S9 in the absence of norharman.