An Autoradiogaphic and Biochemical Study of the Effects of Radiation on Deoxyribonucleic Acid Synthesis in the Intact Animal

Abstract

A study of the effect of localized irradiation on DNA synthesis in the intact animal was made by X-irradiating regenerating rat liver during the first cycle of DNA synthesis following partial hepatectomy with 750 to 40,000 r. There was a rapid depression of DNA synthesis in the lower dose range. Increasing amounts of irradiation resulted in smaller depression of DNA synthesis, suggesting that the eventual depression of DNA synthesis is the result from irradiation effects on different steps in the biosynthetic pathway. Interference with phosphorylation is implicated in the initial rapid depression of DNA synthesis following irradiation. Higher doses of irradiation cause either complete inhibition of DNA synthesis or immediate cell death in some cells. At present, it is not possible to directly relate the effects of irradiation on either synthesizing or non-synthesizing DNA in mammalian cells to eventual cell death. A substantial body of evidence is accumulating from studies on lower organism which suggest the direct effect of irradiation on DNA is related to the problem of cell death from irradiation.