Temporal Change in Radiosensitivity of Miniature Swine as Evaluated by the Split-Dose Technique

Abstract : Using the split-dose technique, recovery was measured in minature swine exposed to whole-body 60Co gamma radiation delivered at 34-35 rads/minute. The initial conditioning dose (150 rads) was approximately two-thirds of the normal LD50/30 (237 rads). The redetermined or challenge LD50/30 measured 28 days after the conditioning dose was 477 rads, indicating 260 percent recovery from the initial sublethal dose. Histopathological examinations of three animals euthanatized 28 days after 150 rads revealed no histologic evidence that could account for the radioresistant state at that time.