The Combined Effects of Ionizing Radiation and High Temperature on the Longevity of the Sprague-Dawley Rat

Abstract

Male Sprague-Dawley rats, individually caged, were exposed to low-level irradiation with chronic dosages from a Co/sup 60/ source for 16 hours a day. The animals were selected by weight and growth rate and divided into eight groups of 22 rats. Four groups were kept at 28 cores consistin 1 C and were exposed to 0.29, 0.64, 2.60, and 4.18 r/day during the irradiation period, which lasted from 4 months of age to 16 months of age. The other groups were kept at 35 cores consistin 1 C during the period of irradiation, which lasted from 4 months of age to 16 months of age, and were exposed to 0.28, 0.60, 2.57 and 3.96 r/day. At 35 C the ET/sub 50/ for 0.29 r/day was 310; for 0.64 r/day it was 490; for 2.60 r/day it was 540; and for 4.18 r/day it was 510. At 28 C the ET/ sub 50/ for 0.28 r/day was 493; for 0.60 r/day it was 510; for 2.57 r/day it was 650; and for 3.96 r/day it was 590. With the exception of the relation between 0.60 and 0.28 r/day, the data are statistically significant at the 5% level. From a previous experiment atmore » 26 C the ET/sub 50/ for 0 r/day was 445, and for 0.8 r/day it was 585. It is suggested that the effects of ionizing irradiation interact with the effects of environment in influencing longevity. (auth)« less