X-irradiation and the incorporation of precursors for salvage and de novo synthesis of DNA in hepatomas and liver.

The effect of X-irradiation 15 Gy (1500 rad) on precursor incorporation into DNA was studied in transplanted Morris hepatomas and liver of the tumor-bearing rats. Precursors were studied which are utilized by salvage mechanisms ([3H] thymidine and [3H]deoxyuridine) or in de novo synthesis of DNA ([14C]aspartate and [14C]formate). The data suggested that salvage mechanisms are more sensitive to inhibition by X-irradiation and that DNA repair activity is greater in liver than hepatomas.