Non-linear Dose—effect Curve for DNA Double-strand Breaks by Low LET Radiation: The Effect of Eluting Buffer Composition on the Measurement of Breaks by the Filter Elution Technique

Summary

Chinese hamster V79 cells were irradiated with 250 kVp X-rays and analysed for the presence of DNA double-strand breaks using filter elution. Changing the pH of the elution and lysis buffers from pH 9·6 to 7·2 leads to a decreased rate of elution of the DNA from the filters and a small difference in the Dose—effect relationship obtained. In both cases the dose–effect curves were non-linear. When cells are irradiated with ²³⁸Pu α-particles a difference in the rate of elution of the DNA is also observed between the two pH values, although the dose–effect curves are linear. These findings suggest that there may be qualitative differences in the types of lesions being induced by low-LET radiation and being scored as dsb in the filter elution assay at pH 9·6. However, carrying out elution at pH 7·2 does not eliminate the nonlinear response measured after X-irradiation.