R. Erikson, W. Szybalski
Oct 1, 1963
Citations
0
Influential Citations
121
Citations
Quality indicators
Journal
Radiation research
Abstract
It has been demonstrated repeatedly that incorporation of 5-halodeoxyuridines, structural analogs of thymidine, markedly augments the radiation sensitivity of transforming DNA (1, 2), bacteriophages (3-5), bacteria (6-9), and animal cells (10, 11). When the halogenated deoxycytidines became available (12, 13) and were shown also to be incorporated into DNA (14-18), a comparison of their radiosensitizing properties with those of the thymidine analogs was undertaken. Since the 5-halodeoxycytidines are incorporated into DNA presumably only after previous metabolic conversion to the corresponding 5-halodeoxyuridines (14-18), the degree of radiosensitization should reflect mainly the comparative metabolic stability of these analogs and the efficiency of their deamination prior to incorporation into DNA. On the other hand, this study constituted an independent check on the relationship between the degree of radiosensitization and the extent of thymidine replacement (9), as well as on the earlier indications of a discrepancy between the ultraviolet light and X-ray sensitization mechanisms; 5-bromodeoxyuridine was by far the most effective ultraviolet light sensitizer, and 5-iododeoxyuridine was the most effective X-ray sensitizer (11). Specifically, a comparison was made between the degrees of incorporation of 5-bromodeoxyuridine (BUdR), 5-bromodeoxycytidine (BCdR), 5-iododeoxyuridine (IUdR), and 5-iododeoxycytidine (ICdR) into the DNA of cultured human cells, as related to the sensitivity of the labeled cells toward ultraviolet light and X-rays of various energy levels.