Rapid repair of potentially lethal damage in normal and ataxia telangiectasia cell lines.

Potentially lethal damage repair (PLDR) was investigated in two normal and three ataxia telangiectasia (AT) human-skin fibroblast cell lines cultured in vitro. Using plateau-phase cells, both the time kinetics and the amount of repair were measured after irradiation. PLDR depended on both dose and survival level, as previously seen in rodent cells. Human cells differed from rodent cells in PLDR speed and the ability to discern two components within the repair response. Fast repair had a t1/2 of approximately 5-7 min while the slow response occurred over hours. AT cells had demonstrable PLDR in contrast to previous studies. Quantitatively, the proportion of fast and slow repair was similar for each dose in either normal or AT cells. However, AT cells had lower levels of both types of repair. When analyzing PLDR in human cells, differences in the rate of repair between human and rodent cells must be taken into account.