DNA strand breaks in resistant and sensitive murine lymphoma cells detected by the hydroxyapatite chromatographic technique.

Strand breaks were determined in L5178YS and L5178YR cell lines with DOS of 0.75 and 1.75 Gy, respectively, for 7 MeV electrons. The hydroxyapatite chromatographic technique was used to measure the breaks produced by 7 MeV electrons or 7 MeV neutrons immediately after irradiation or after maximal repair. Oxygen enhancement values for survival as well as strand breaks were determined for both cell lines and both qualities of radiation. The results indicate that despite a differential response to the lethal effects of radiation the levels of DNA strand breaks induced in these two lines were identical. Furthermore the values obtained for oxygen enhancement ratios (o.e.r.) and relative biological effectiveness (r.b.e.) for DNA strand breaks were different from those for cell survival. These results show that the difference in radiation sensitivity for cell killing is not reflected by the extent of DNA strand breaks measured by this method.