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 (CH O) cell lines) each comprising a cell line with a normal radiation res ponse and a radiation-sensitive mutant, were evaluated for recovery of potentially lethal damage (PLDR) and recovery of sublethal damage (SL DR). 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 l ines. Postirradiation exposure to hypotonic NaCl solutions resulted in fixation of radiation damage in all the cell lines. This form of dama ge is repaired if left unperturbed after irradiation. This shows that cells have a large capacity for repair of this form of damage which ac counts for much greater changes in survival than those observed in con ventional 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, i nitial (i.e. preirradiation) DNA polymerase activities were measured i n the four CHO cell lines; they were not correlated to radiation sensi tivity.