The effect of postirradiation holding at 22°C on cell growth, progression of cells through the cell cycle, and the repair of sublethal, potentially lethal and potentially neoplastic transforming damage in γ-irradiated HeLa x skin fibroblast human hybrid cells has been examined. Cell growth and cell cycle progression were essentially stopped at this reduced temperature. Cell survival was dramatically reduced by holding confluent cultures for 6 h at 22°C, as opposed to 37°C, after 7.5 Gy γ radiation delivered at a rate of 2 Gy/min. Return of the cells to 37°C for 6 h after holding at 22°C did not result in increased survival. A similar effect was obtained when the cells were held at 22°C between split-dose irradiation of log-phase cultures where no increase in survival was observed over a split-dose interval of 4 h. In this case a partial increase in survival was observed upon returning the cells to 37°C for 3 h after holding at 22°C for the first 3 h of the split- dose interval. Neoplastic transformation frequency was not enhanced by holding confluent cultures for 6 h at 22°C after 7.5 Gy γ radiation. This is consistent with previous observations that misrepair of potentially neoplastic transforming damage already occurs at 37°C. The overall results are interpreted in terms of the reduced temperature favoring misrepair, rather than inhibition of repair, of sublethal, potentially lethal and potentially transforming radiation damage.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging