Thiol radioprotectionin vivo: the critical role of tissue oxygen concentration

Lunec et al. (1981) have recently pointed out that when exogenous free thiols are added to cells they have a marked radioprotective effect on cells at an intermediate radiosensitivity, and have less effect on aerobic radiosensitive cells or on hypoxic radioresistant cells. The oxygen concentration at which the maximum protection occurs corresponds to the K value for these cells. They caution that a considerable radioprotection of tumours, as was reported by Rojas and Stewart (1981), at low radiation doses might be expected if tumour cells are at such an intermediate oxygen tension.