Postirradiation exposure to hypotonic saline shows normal damage processing in radiation-sensitive cell lines.

Three pairs of cell lines (one human and two Chinese hamster ovary (CHO) cell lines) each comprising a cell line with a normal radiation response and a radiation-sensitive mutant, were evaluated for recovery of potentially lethal damage (PLDR) and recovery of sublethal damage (SLDR). In all cases, the normal cell lines (GM1522, human; AA8-4 and K1, CHO) exhibited capacity for PLDR and SLDR was also normal in the two CHO lines. For the mutants (GM3395, human AT; V3 and 5-11, CHO) there was no ability for PLDR and SLDR was also absent in the two CHO cell lines. Postirradiation exposure to hypotonic NaCl solutions resulted in fixation of radiation damage in all the cell lines. This form of damage is repaired if left unperturbed after irradiation. This shows that cells have a large capacity for repair of this form of damage which accounts for much greater changes in survival than those observed in conventional PLDR experiments. These data show that the mutant cell lines retained their capacity to repair the damage which was susceptible to postirradiation fixation by anisotonic salt solutions. In addition, initial (i.e. preirradiation) DNA polymerase activities were measured in the four CHO cell lines; they were not correlated to radiation sensitivity.