Protection of cultured Chinese hamster ovary cells by the aminothiol WR-255591 from the lethal and DNA-damaging effects of fast neutrons.

We examined the radioprotective effect of the aminothiol WR-255591 on cultured aerated Chinese hamster ovary cells irradiated with cyclotron-generated fast neutrons. The effects of a 30 min pretreatment with 6 mM WR-255591 on the induction of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) were measured using alkaline (pH 12.1) and neutral (pH 7.0) filter elution, respectively. Molecular protection factors (PFs) calculated from these data were compared with the PF measured using the biological endpoint of cell survival. WR-255591 afforded significant protection against cell killing by neutrons (PF = 1.36) although protection was less efficient than against cell killing by gamma-rays (PF = 2.30). Whereas for gamma-rays, the PFs were in the order survival greater than or equal to DSB induction much greater than SSB induction, the magnitude of the modification of the induction of both SSBs (PF = 1.38) and DSBs (PF = 1.38) after neutron irradiation was the same as that of cell killing.