Evidence for Similarities between Radiation Damage Expressed by β-araA and Damage Involved in the Interaction Effect Observed after Exposure of V79 Cells to Mixed Neutrons and γ Radiation

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Abstract
Plateau-phase V79 cells were exposed sequentially to fast neutrons and .gamma. rays. A dose-dependent reduction in the shoulder width of the .gamma.-ray survival curve was observed after preexposure of cells to neutrons. A similar effect was demonstrated on the neutron survival curve when cells were preirradiated with .gamma. rays. Treatment of cells with 150 .mu.M .beta.-araA after either .gamma. or neutron irradiation reduced primarily the shoulder of the survival curve. When .beta.-araA was given to the cells after exposure to mixed radiation modalities, survival curves similar to those observed after exposure to a single radiation modality and treatment with .beta.-araA were obtained. The kinetics of loss of the interaction observed after exposure of cells to .gamma. rays following neutron irradiation was similar to the kinetics of loss of sensitivity to .beta.-araA (T1/2 = 1 h) measured by delaying drug administration after exposure to .gamma. rays. The results suggest that the PLD expressed by .beta.-araA is at least partly involved in the interactive effect observed after combined exposure of plateau-phase V79 cells to neutrons and .gamma. rays.