In order to study the mechanism of radiobiological effects
the inverse pulsed-field gel electrophoresis has been applied to separate DNA from hepatoma SMMC-7721 cells cultured for various hours after exposed to γ -ray. Results showed that
in the samples repaired for 0 and 24 hours
the percentages of DNA released from plug (PR) increased with dose. The fragments were mainly 1-2Mbp and the yields of DSB in the two kinds of samples were 0.38DSBs/100Mbp· Gy and 0.06DSBs/100Mbp·Gy
respectively. Thus 84% DSBs were rejoined. In the samples repaired for 48 hours
the remaining DSB fragments induced with different doses were similar to the control and seem to have nothing to do with dose. It is elucidated that DSBs induced by γ -ray are easy to be rejoined and the remaining DSBs are the cause of cell death.