| Abstract
| - We report data in this paper suggesting that fish irradiatedto 0.5 Gy total body dose can release factors into thewater that signal other unexposed fish and cause inductionof bystander effects expressed as increased cell deathin a reporter system. Radiation-induced bystander effects,resulting in the appearance of radiation damage orinduction of typical radiation responses in unirradiatedcells and tissues are now an established consequence ofexposure to low doses of ionizing radiation, howeverlittle work has been done in vivo or in species other thanhumans or mice. In these experiments rainbow troutwere irradiated and then paired with unirradiated fish fortwo hours. Additionally, unirradiated fish were placed inwater which had previously been used to hold irradiated fishfor 2 h. Sham-irradiated fish and absolute control fishwere also examined all using blind protocols. Following atwo h incubation period, at these various exposureregimes, the fish were killed by a blow to the head anddissected. Five organs were removed from each fish andtissue explants were cultured using an established technique.After 2 days, the culture medium was harvested andused in a reporter assay to determine whether a bystandereffect had been induced. The explants were cultured onin Clonetics growth medium for a further 14 days then fixedfor assay of radiation response proteins. The responsesvaried according to the cell type in the original explants, withthe gill and fin showing the most pronounced response.The results suggest that communication signals leading toa typical radiation response can be passed between fishand seem to involve secretion of a chemical messenger intothe water.
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