RESUMO
The Non-genotoxic Carcinogen Study Group of the Environmental Mutagen Society of Japan organised the first step of an interlaboratory validation study on an improved cell transformation assay employing Balb/c 3T3 A31-1-1 cells. Nineteen laboratories participated in this study. The modified transformation assay was evaluated for its responsiveness, its interlaboratory reproducibility and its transferability. In this study, a mixture of Dulbecco's modified Eagle's medium and nutrient mixture F12, supplemented with insulin-transferrin-ethanolamine-sodium selenite and 2% fetal bovine serum (FBS) was used during the period of expression of transformed foci, intead of the usual minimum essential medium with 10% FBS. 20-Methylcholanthrene (MCA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) were selected as a prototype initiator and a tumour promoter, respectively. Two series of experiments were conducted. In the first series, the transformation activity of MCA was examined at various concentrations. In the absence of the promoting treatment with TPA, exposure to MCA only weakly induced transformed foci. In the presence of 0.1µg/ml TPA, all laboratories observed significant dose-dependent increases in the number of transformed foci with increasing MCA concentrations. In the second series of experiments, various concentrations of TPA were tested. In the absence of initiating treatment with MCA, exposure to TPA weakly induced transformed foci in about half of the laboratories. In the presence of 0.2µg/ml MCA, all the laboratories observed significant dose-dependent increases in the number of transformed foci with increasing TPA concentrations. The results from this study support the usefulness of this modified two-stage transformation assay with Balb/c 3T3 cells.
RESUMO
Environmental pollution by pentachloronitrobenzene (PCNB) was investigated at Tsumagoi, an intensive farming area, where a great amount of PCNB has been applied. High concentrations of PCNB were detected in river water near an area of cabbage cultivation. Further, pentachloroaniline (PCA) and pentachlorothioanisole (PCTA), which are the principal biodegradation products of PCNB, were also detected, and their ratios to PCNB were higher in autumn than in summer. PCNB concentrations in soil were similar to those of river sediment, in which PCNB was concentrated 5000-10,000 times over levels in river water. The biodegradation rate of PCNB in river water was higher than in river sediment and soil. The formation rates of PCA from PCNB were higher in river sediment and soil than in river water. It is considered that PCA remains for a long time in the environment and accumulates in river sediment and soil.
