Recovery from Radiation Injury in Swine as Evaluated by the Split-Dose Technique

摘要

With 1 Mvp X rays, the acute LD50/30 (midline air dose) of 8-9 month old Duroc gilts was determined to be 399 R (95% confidence interval: 371-424 R). The pattern of recovery from the effects of 240 or 265 R of X rays was studied by means of the split-dose technique, which consists of conditioning the animals with a sublethal exposure and redetermining the LD50 at various times thereafter. By this criterion, the swine had recovered from 51% of the initial injury by three days. By seven days, they appeared to have recovered from about 65% of the initial injury, but the data suggest that part of the population had recovered completely while part was still about as sensitive as at three days. By twenty days, the entire population appeared to be radioresistant: the redetermined LD50 was 164% of the LD50 of unconditioned animals. Radioresistance was also evident at 61 and 107 days: at 61 days, 734 R killed eight out of 15 animals conditioned with 265 R whereas, the same exposure killed 15 of 15 unconditioned animals; at 107 days, none of nine conditioned animals died after 399 R. The pattern of systemic recovery and the period of radioresistance are not clearly reflected in the pattern of hematological changes that follow a conditioning exposure. (Author)