HeLa S3 cells were sensitized to the lethal action of 220-kV X rays by partially replacing the thymidine in their DNA with 5-bromodeoxyuridine (BrdU). To examine the expression of and recovery from potentially lethal radiation damage (PLD), both BrdU-grown and control cells were treated with 4 mM caffeine for increasing times up to 2 days, either immediately after irradiation or after increasing delays up to 28 h. When the same dose of X rays (3 Gy) was applied to BrdU-grown and control cells, the difference in survival that is found in the absence of caffeine disappeared after about 30 h of incubation in its presence; when isosurvival doses were applied (BrdU-grown cells, 2.5 Gy; control cells, 4 Gy), the control cells suffered more killing. When treatment with caffeine was delayed for progressively longer times after both groups of cells received 3 Gy, the control cells achieved a higher level of survival. These results indicate that the increased radiation sensitivity of cells containing BrdU derives from a decreased ability to repair PLD.
The Action of Caffeine on X-Irradiated HeLa Cells: X. Depressed Recovery from Potentially Lethal Damage in Cells Containing 5-Bromodeoxyuridine
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Jadwiga Labanowska, Karen L. Beetham, L. J. Tolmach; The Action of Caffeine on X-Irradiated HeLa Cells: X. Depressed Recovery from Potentially Lethal Damage in Cells Containing 5-Bromodeoxyuridine. Radiat Res 1 August 1990; 123 (2): 228–231. doi: https://doi.org/10.2307/3577550
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