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  • Title: Increased DNA synthesis in INIT/10T1/2 cells after exposure to a 60 Hz magnetic field: a magnetic-field or a thermal effect?
    Author: Zhao YL, Johnson PG, Jahreis GP, Hui SW.
    Journal: Radiat Res; 1999 Feb; 151(2):201-8. PubMed ID: 9952305.
    Abstract:
    This study was designed to test the hypothesis that a 0.1-0.8-mT 60 Hz magnetic field may act as a promoter of carcinogenesis. C3H 10T1/2 mouse fibroblasts initiated with the carcinogen methylcholanthrene (INIT/10T1/2 cells) were used; in these cells, expression of the carcinogenic phenotype is suppressed indefinitely by the presence of retinyl acetate in the culture medium. After withdrawal of retinyl acetate, expression of the carcinogenic phenotype may be observed as the loss of contact inhibition. Cells grown without retinyl acetate were exposed to 0.1-0.8-mT (rms) 60 Hz magnetic fields or to sham fields. Eight days after exposure, magnetic-field and sham-exposed cells showed the same levels of incorporation of [3H]thymidine, and both had counts significantly higher than those of unexposed cells. The rate of incorporation of [3H]thymidine was very sensitive to small (0.1-0.8 degrees C) and transient (60 min) increases in incubation temperature during the first few days of withdrawal of retinyl acetate. Exposure of Jurkat (human acute T-cell lymphoma) and GH3 (rat pituitary tumor) cells to magnetic fields and sham conditions yielded similar results. INIT/10T1/2 cells cultured in the presence of retinyl acetate showed no effect of exposure conditions. Both magnetic-field and sham exposures caused a slight increase in temperature within the exposure zone in the incubator. Thus the differences between rates of incorporation of [3H]thymidine in magnetic field-exposed, sham-exposed and unexposed cells seem to be attributable at least in part to a slight elevation in temperature during exposure. Since some cells appear to be extremely sensitive to small increases in temperature, measurements of magnetic-field effects must be made and interpreted with caution.
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