DNA Repair of Radiation Damage

Abstract
The therapeutic effect of DNA from different sources, such as calf thymus, rat liver and spleen, herring and salmon sperm and Ehrlich ascites-carcinoma cells was studied on Wistar rats given lethal doses of gamma-irradiation. A single injection of DNA was administered intraperitoneally 24 hours after irradiation. All forms of DNA significantly increased the survival of the irradiated rats. The quantitative differences in the effects of DNA from different sources were directly related to their molecular weight. When native calf-thymus DNA was sheared or denatured, there was a reduction in its therapeutic efficiency proportional to the reduction in molecular size. Therefore heterologous as well as homologous DNA have a marked therapeutic effect which is quantitatively dependent on their molecular weight.