The saturated repair kinetics of Chinese hamster V79 cells suggests a damage accumulation--interaction model of cell killing.
The aim of this study is to determine whether the repair process in log-phase Chinese hamster V79 cells exposed to X rays is unsaturated, saturable, or saturated. The kinetics of recovery from damage induced by 2 to 14 Gy of 250 kVp X rays was studied by treating cells with 0.5 M hypertonic saline for 20 min at different postirradiation repair intervals. From the kinetic data, the repair half-time (t1/2), the repair time (time needed to attain maximal survival), and the recovery ratio were calculated. The results show that the t1/2 (1.42 min/Gy) and the repair time (6.04 min/Gy) increase linearly with dose, the logarithm of the recovery ratio increases linear-quadratically with dose, and the D0 increases linearly with repair interval at a rate of 2.4 cGy/min. From these results we suggest a model: the repair of damage (undefined lesions) necessary for cell survival is effected by a repair process (t 1/2 of 1.42 min/Gy) which is saturated at doses as low as 2.4 cGy; repair saturation leads to a dose-dependent accumulation of repairable lesions; and interaction among accumulated repairable lesions results in the induction of irreparable (lethal) lesions. We call this the accumulation-interaction model of cell killing by low-LET radiation.
Reddy
N M
NM
Department of Radiation Oncology, SUNY Health Science Center, Brooklyn 11203.
Mayer
P J
PJ
Lange
C S
CS
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D007700:Kinetics; D011829:Radiation Dosage; D013997:Time Factors