DOSE-RESPONSE IN NEUTRAL FILTER ELUTION

In neutral filter elution a nonlinear relationship between fraction of eluted DNA and dose is usually observed, which is often interpreted as a nonlinear induction of DNA double-strand breaks (DSBs) with dose. The conclusiveness of this hypothesis is questioned here on the basis of theoretical considerations regarding the size distribution of DNA fragments. A simple hydrodynamic model is proposed which generates the typical features of the dose response of neutral filter elution: (1) the shoulder at low doses, (2) a quasilinear correlation in an intermediate dose range, (3) a saturation at high doses, and (4) a linearization of the curve in the intermediate and higher dose range in a semilogarithmic plot. These features were derived even with the assumption of a linear induction of DSBs with dose. Thus it is demonstrated that the fraction of eluted DNA could conceivably be a nonlinear function of dose even if the induction of DSBs is directly proportional to the radiation dose.