Cytotoxicity, cellular transformation and DNA adducts in normal human diploid fibroblasts exposed to 1-nitrosopyrene, a reduced derivative of the environmental contaminant, 1-nitropyrene

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Abstract
Treatment of normal human diploid fibroblasts with 0.3 — 22 μM 1-nitrosopyrene resulted in a dose-dependent decrease in relative cloning efficiency and an increase in anchorage-independent growth in soft agar. When compared to previous experiments, 1-nitrosopyrene was 10- to 20-fold more cytotoxic and 5- to 10-fold more potent at inducing morphological transformation than 1-nitropyrene. Incubation of the fibroblasts with 8 μM 1-nitropyrene in the presence of xanthine oxidase, a mammalian nitroreductase, resulted in the formation of one major DNA adduct, N-(deoxyguanosin-8-yI)-1-aminopyrene, at a level of 1.1 adducts per 10 6 nucleo-tides. Fibroblasts treated with 1-nitrosopyrene formed the same DNA adduct; however, only a 0.3 μM concentration was required to give 0.7 adducts per 10 6 nucleotides in the fibro-blast DNA. These data indicate that a limiting step in the cellular toxicity and transformation of normal human diploid fibroblasts by 1-nitropyrene is the initial reduction to 1-nitrosopyrene.

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