The initiator tRNA acceptance assay as a short-term test for carcinogens. 3. Results with 69 N-nitroso compounds

The activity of 69 carcinogenic and non-carcinogenic N-nitroso compounds was tested by the recently developed initiator tRNA acceptance assay for carcinogens. Of 51 carcinogens tested, 50 were active in the assay. Only N-nitrosopropylpropanolamine showed a false negativity. Eleven out of 14 tested non-carcinogenic compounds were not active in the assay, nitrosoethyl-tert-butylamine and nitrosoprolineethylester were positive. As calculated from these data, the sensitivity of the assay was 98.0%, specificity 84.6%, accuracy 95.4% and predictive value 94.4%. Comparison of relative carcinogenicities in animal bioassays with quantitative results (% stimulation of initiator tRNA charging) of the short-term test showed a good correlation for non-carcinogenic compounds and strong carcinogens. However, carcinogens of low and median potency could not be easily distinguished. A good correlation was obtained for three isomer N-nitrosomethylaminopyridines between the TD50-value and activity in the tRNA acceptance assay. The initiator tRNA acceptance assay thus seems preferable for recognizing and classifying carcinogenic and non-carcinogenic N-nitroso compounds than any other individual short-term test for carcinogenicity.