Protective and Sensitizing Effects of D2O Treatment on Thermal Responses of Chinese Hamster Cells

Hyperthermia/Deuterated water (D2O)/Thermal protection and sensitization/chinese hamster cells Modification of thermal sensitivity by deuterated water (D2O) was examined in Chinese hamster V-79 cells. When cells were exposed to hyperthermia at 44°C in a medium containing 20 to 85% D2O, cell survival was remarkably increased. Thus, D2O applied during hyperthermia resulted in thermal protection. However, when cells were treated with D20 (50%) medium for 4 to 24 hours and then exposed to hyperthermia in normal medium, thermal sensitization was observed. Increasing interval time at 37°C between D2O and hyperthermic treatments, the thermal sensitization was rapidly reduced and reached to the normal level in about 4 hours of the interval. On the other hand, thermotolerance induced during step-up heating (42→ 44°C sequence) was reduced by pretreatment of cells with 50% D2O medium for 4 or 24 hours. In split hyperthermia (44 → 44°C sequence) experiments, when cells were incubated at 37°C for 24 hour-interval in 50% D2O medium, survival of cells was markedly reduced, and the shoulder of the survival curve almost disappeared.