Low Oxygen Enhancement Ratios for Strand Breaks Induced by Decays of 125I in DNA of Human T1 Cells Stored at 0°C

After incorporation of 125I into DNA of T1 cells, these cells were transferred into serum free medium where decays of 125I were accumulated at 0 °C under aerobic or hypoxic conditions. The unwinding technique was used for strand break measurements with ethidium bromide as a marker for double stranded DNA. Exposure of the cells to 1,500–14,000 decays, over periods of 4–7 days, gave an OER close to 1. Ideas about the nature of this phenomenon are discussed.