Differences in survival of mouse colon crypts after whole- or partial-body irradiation.

The survival of mouse colon crypts after X-irradiation has been studied by the microcolony technique. The Do for crypt survival was 266 rad after whole-body irradiation in air, but when the colon alone was irradiated, the Do was 340 rad. In mice which were breathing 95 per cent oxygen, the Do values were 238 rad for whole-body and 302 rad for colon irradiation. The survival curves were all extrapolated to the same number, and the DQ was also increased with colon irradiation. There was, therefore an enhancement of colon crypt survival of about 27 per cent by local as opposed to whole-body irradiation. These results might be explained by a circulating repair promoter or by the production of a toxin after whole-body irradiation.