Deuterium Oxide Enhancement of Chinese Hamster Cell Response to γ Radiation

Abstract

Exposure of Chinese hamster cells to growth medium containing D2O following .gamma. irradiation has a dramatic effect on the response to radiation. Increasing the D2O concentration and the time of exposure enhances the radiation response in a dose-modifying manner. The dose-modifying factor (DMF) is about 4.5 for 3 h at 90% D2O. Preirradiation incubation under the same conditions has only a small effect on radiation response. The potentiating effect of D2O depends on cellular metabolism. It is smaller when incubation is in buffer instead of growth medium, is reduced at temperatures below 37.degree. C and is virtually absent at 4.degree. C. The radiation damage interacting synergistically with D2O is repaired by the cells in about 3 h at 37.degree. C in growth medium. The rate of repair is slower at 20.degree. C in buffer and no repair exists at 4.degree. C. Split-dose experiments suggest the cells have a reduced capacity to repair radiation-induced sublethal damage in the presence of 90% D2O. Heat sensitivity (42.degree. C) is not affected by D2O and enhancement of radiation response by heat is independent of enhancement by D2O.