Co-carcinogenicity of sodium saccharin and N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide for the urinary bladder

The co-carcinogenic activity of sodium saccharin and N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide(FANFT) was evaluated in male Fischer rats by co-administeringthem as 5% and 0.005% of the diet, respectively, for 2 years.The effect of simultaneous administration of two urinary bladderpromoting substances, sodium saccharin and L-tryptophan as 5%and 2% of the diet, respectively, was also evaluated. Five of16 rats administered sodium saccharin plus FANFT developed bladdertumors whereas none of the rats administered FANFT, sodium saccharin,or L-tryptophan alone, sodium saccharin plus L-tryptophan, orthe control diet developed bladder tumors. Possible mechanismsfor the co-carcinogenic activity of sodium saccharin and FANFTare discussed.