Acute X-Ray Lethality Studies with the Hamster. The LD 50 , Death Rate, and Recovery Rate

Abstract

Adult Golden Syrian hamsters, 105 to 240 days old, were irradiated with 250-kvcp X-rays, 414 to 828 r whole-body exposure. No significant sex difference was noted. Of the 6 week mortality 96% occurred prior to day 28. The estimated values of the LD50/40 and the slope function, S, of the probit-transformed dose-effect (killing) curve were 611 r and 1.13, respectively. The relation between log killing time and tissue dose was linear for doses of 85 to 135% of the LD50. For the LD15-LD99 range, the death-rate curves had 2 peaks, a major one occurring at 8 to 11 days and a minor one at 16 to 19 days after irradiation, suggesting the existence of 2 different modes of death. Recovery from an average tissue dose of 322 r was 18% 3 days after exposure and 65% 7 days after exposure, as determined with a 2-exposure technique. The rate of recovery was not an exponential function of time during this period. The best estimate of the time for 50% recovery was approximately 6 days.