Dependence of Rate of Recovery from Acute Gamma-Ray Exposure on Size of the Conditioning Dose

Abstract

A homogeneous population of 4658 RF female mice was used to study rate of recovery from acute Co60 gamma-ray exposure and its dependence on the magnitude of the first or conditioning dose. The time required for mice given a conditioning dose of 205 r to repair 50% of the effect was 181 [plus or minus] 18 hours, and the recovery rate was fit best by a linear expression. The recovery half-time (RT50) for mice conditioned with 600 r of gamma-rays was 161 [plus or minus] 20 hours, and the recovery rate was fit best by an exponential expression. The 50% recovery times were not significantly different. Mice given gamma-ray exposures ranging from 205 to 692 r showed an average residual damage of 48% of their initial exposure after 144 hours of repair. There were no significant variances in the per cent residual damage regardless of the size of the conditioning dose. It was concluded that the time required for RF female mice to repair one-half of the radiation damage from acute Co60 gamma-ray exposure was 7.0 days and that the RT50 was not influenced by the magnitude of the conditioning dose between the dose levels of 205 and 692 r.