Fibroblasts from ataxia telangiectasia (AT) and AT heterozygotes show an enhanced level of residual DNA double-strand breaks after low dose-rate gamma-irradiation as assayed by pulsed field gel electrophoresis

Int J Radiat Biol. 1991 Nov;60(5):791-802. doi: 10.1080/09553009114552601.


Skin fibroblasts from ataxia telangiectasia (AT) patients, obligate AT heterozygotes (ATH) and normal individuals were studied for colony-forming ability and repair of DNA double-strand breaks (dsb) after gamma-irradiation. AT cells were three to four times more radiosensitive than normal cells at high and low dose-rate exposures; ATH cells, however, showed a marginally increased radiosensitivity after high dose-rate gamma-irradiation and an intermediate response after low dose-rate exposure. The repair of DNA dsb was studied by pulsed field gel electrophoresis. After high dose-rate gamma-irradiation the repair time constant (t1/2) was around 1 h for normal, ATH and AT cells. After low dose-rate gamma-irradiation the fraction of residual dsb was 1.4% for normal, 2.1% for ATH and 5.2% for AT cells, demonstrating a deficiency in the repair of a small fraction of dsb in AT. Thus the fraction of residual dsb after low dose-rate exposure was not only four times higher in AT than in normal cells, but was also significantly increased in ATH compared to normal cells.

MeSH terms

  • Ataxia Telangiectasia / genetics
  • Ataxia Telangiectasia / pathology*
  • Cell Survival / radiation effects
  • Cobalt Radioisotopes
  • DNA / radiation effects*
  • DNA Damage*
  • DNA Repair
  • Dose-Response Relationship, Radiation
  • Electrophoresis, Gel, Pulsed-Field
  • Fibroblasts / radiation effects
  • Gamma Rays
  • Heterozygote*
  • Humans


  • Cobalt Radioisotopes
  • DNA