[Reorganization of DNA replicating system induced by 5-fluorodeoxyuridine and caffeine as the basis for...

Treatment of diploid human fibroblasts with 5-fluorodeoryuridine (FUdR) and caffeine results in the increase in cellular radiosensitivity in terms of survival and chromosomal aberrations, on the one hand, and in radioresistant DNA synthesis (RDS), on the other hand, i.e. rather mimics those in mutant cells from patients with AT, XPII, Down syndrome, and others. A study was made of the autoradiographic length of simultaneously active adjacent replicon clusters. After incubation of diploid human cells with FUdR (10(-6) M, 6 h), this parameter was shown to reduce by two-fold, remaining unchanged upon 5 Gy irradiation. In contrast, after incubation of the cells with caffeine (2 mM, 30 min), this parameter was longer, compared to that in intact cells; upon 5 Gy irradiation the values remained almost the same as in the control. A possible relation of the data to the cellular radiosensitivity and RDS in the cells incubated with FUdR and caffeine is discussed.