The Response of Twenty-Seven Inbred Strains of Mice to Daily Doses of Whole-Body X-Irradiation

Abstract

At various times throughout a 12-month period, males and females from 27 inbred strains were subjected to daily doses of 100 r of x rays until death. The strains with longer survival times had survival distributions with the mode skewed in the upward direction. The deaths of the shortsurviving mice in the longer surviving strains occurred mainly in the months of May through October. The greater within-strain variance and lesser difference between means during the warmer months caused a significant seasonal shift in heritability. Heritability was +0.52 in the cooler months. Males survived 1.6 days longer than females under this dose schedule. Some of the strains studied were found to be considerably more resistant to irradiation than the strains previously studied; the upper limit of resistance of inbred strains was therefore extended. The rank order of survival times of the strains agreed well with published data on single- dose LD/sub 50/, on life span, and on litter size, suggesting that radiation resistance is a good indicator of general fitness. Conversely, it was concluded that the radiation resistance which could be manifested by a genotype could be estimated by the manifestations of that genotype in other fitness traits. (auth)