The rejoining of DNA double-strand breaks following irradiation with 238Pu alpha-particles: evidence for a fast component of repair as measured by neutral filter elution.

The induction and repair of DNA double-strand breaks (DSB) following exposure to 238Pu alpha-particles was examined in V79-379A cells. The technique of neutral filter elution was used in these investigations at both pH 9.6 and pH 7.2. The initial dsb yield was found to be similar to that seen after 250 kVp X-ray or 2.3 MeV neutron exposure. However, the pattern of dsb rejoining after alpha-particle irradiation did not follow that seen after X-rays or neutrons. A very fast initial component, complete within 2 min of incubation following irradiation, removed 70 per cent of the dsb seen after 40 Gy alpha-particles; very little slow rejoining was seen. This contrasts sharply with the dsb rejoining seen after X-ray or neutron exposure, and presumably reflects the differences in the nature of the dsb induced and the way they are repaired.