Abstract
The incorporation of labeled precursors into the DNA is often believed to be the indicator of the DNA synthetic rate. However, the detailed kinetic changes in incorporation immediately following irradiation has been not observed.
In this experiments, the radiation-induced changes of DNA precursor incorporation (3H-TdR) was pursued concerning the labeled index and the grain count in labeled tumor cells (Yoshida ascites tumor) .
As the result,
1) Incorporation immediately after irradiation (500-1000R) was a dose-independent phenomenon, namely irradiation has no influence upon the thymidine incorporation into DNA injected immediately following irradiation.
2) In irradiated early S-phase cell (or late G1-phase cell), it was likely that TMP de novo synthesis was inhibited, and salvage was increased.
