TREATMENT      MUTANT FREQUENCY (x 10-6) 2-nitrofluorene (µg/mL) NAT2(S)/GSTM1(+) NAT2(R)/GSTM1(-) 0 3.48 6.39 100 n.d. 12.6 200 3.95 26.8 400 4.95 30.5 500 1.98 n.d. NAT2(S)/GSTM1(+):N-acetyltransferase 2 slow and glutathione S-transferase M1 positive NAT2(R)/GSTM1(-):N-acetyltransferase 2 rapid and glutathione S-transferase M1 negative n.d. = not determined due to low or excess cytotoxicity

Table 1: HPRT mutant frequency induced by various concentrations of 2-nitrofluorene in human peripheral lymphocytes with two different genotype combinations.