DNA Damage and Repair Following Irradiation: The Effect of 5-Bromodeoxyuridine in Cultured Chinese Hamster Cells

Abstract

Cell cultures, in exponential growth, were pretreated with noncytotoxic concentrations of the thymidine analogue 5-bromodeoxyuridine ( $1.0-3.0\times 10^{-7} M$ ) for ∼12 generations. Two forms of DNA damage and repair following radiation were evaluated by analysis of the sedimentation patterns of the DNA released during lysis on preformed alkaline sucrose density gradients. DNA released from cells grown in the presence of 5-bromodeoxyuridine was more susceptible to degradation by alkali (no irradiation). In irradiated cells, the production and repair of single-strand breaks in DNA were not significantly affected by 5-bromodeoxyuridine pretreatment. The low-dose radiation effect on DNA-i.e., the acceleration of the release in alkali of denatured DNA from a complex of associated cellular material by doses less than ∼700 rad-also may not have been affected by the incorporation of 5-bromodeoxyuridine. However, the repair of this low-dose radiation effect on the DNA complex was reduced in ...