Molecular Radiobiology of Human Cell Lines: IV. Variation in Ultraviolet Light and X-Ray Sensitivity during the Division Cycle

Abstract

Cell division in a human cell culture was partially synchronized by temporarily inhibiting thymidylic acid synthesis. The X-ray and UV sensitivities of such synchronized cells vary during the replication cycle according to a specific pattern. The period of greatest radioresistance follows immediately the completion of DNA synthesis, preceding cell division. 5-Bromodeoxyuridine incorporated into DNA radiosensitizes the cells independent of the stage in the division cycle.