MP7 Toxicogenomics in Environmental Studies
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(KIL-1117-733691) Screening of teleost cell lines for bystander effects of low–dose radiation – preliminary results of a 5-year study.

Kilemade, M.¹, O'Neill, A.¹, Mothersill, C.¹, Seymour, C.¹, ¹ McMaster University, Hamilton, Ontario, Canada

ABSTRACT- Bystander effects are detected in cells, which were not themselves exposed to radiation but were exposed to signals from exposed (irradiated) cells. They involve expression of many endpoints associated with genomic instability. Now that the existence of radiation–induced bystander effects is not in doubt, the problem for regulators is to assess their importance. Previous work by people in this group suggests that these effects dominate the low dose region of the dose–response curve, and saturate at low doses (less than 5mGy). These effects occur in many cell types and species following high–or low–linear energy transfer radiation exposures. The signals produced are capable of inducing death, genomic instability, mutations, or transformation in cells not directly hit by radiation themselves. The effect may be important in radiation protection of both human and non–human biota and may impact on low dose and low dose rate risk estimates. Bystander signals are now considered by many authors to drive genomic instability. In this study a range of teleost fish cell lines were exposed to a low radiation dose range (0.002–5 Gy). Clonogenic survival was measured in the exposed cells and in the distant progeny of exposed cells to assess early and delayed cell death. Clonogenic survival was also measured in cultured cells, which received culture medium from irradiated cells to determine bystander effects. Our preliminary data have shown that the dose response curves for the fish cells exposed to radiation demonstrated the bystander effect. These results demonstrate that damage due to low doses of radiation occurs both directly and indirectly and may have implications for radiation and environmental protection of biota.

Key words: fish cells, radiation, bystander effects, genomic instability