Results of an interlaboratory trial of 32P-postlabelling

An interlaboratory 32P-postlabelling trial involving 15 independent investigators was conducted. Each participant was provided with four DNA samples: 1, control DNA; 2, benzo[a]pyrene-modified DNA from mouse skin; 3, DNA from the lung of a tobacco smoker; 4, 2-acetylaminofluorene-modified DNA from mouse liver. The participants analysed the DNA samples by 32P-postlabelling using the standard procedure and using two procedures, nuclease P1 digestion and butanol extraction, to enhance the sensitivity of the assay. The qualitative and quantitative reproducibility of the results obtained by the different investigators are presented. A workshop discussion on postlabelling procedures is summarized.