Dependence of AP site, N7POBG and O2POBdT formation on NNKOAc concentration. Liver or lung homogenates (~100 mg) were incubated with 0 (control), 2 12, 49, and 243 μM NNKOAc for 1.5 h. Esterase was added to catalyze the release of NNK-OH from NNKOAc. Each concentration level was performed in triplicate. Relative to controls, significant increases in AP sites were observed in liver and lung incubated with 49 μM and 243 μM of NNKOAc (p<0.05).