Because the Mongolian gerbil (Meriones unguiculatus) survives more than twice as long as the mouse after doses of ionizing radiation sufficient to cause GI death, a correlation between survival time and the rate of development of the fatal lesion has been postulated. Autoradiographic methods were used to follow labeled epithelial cells as they migrated from the base of the crypts to the tips of the villi in the terminal ileum and to compare renewal rates for both normal and sublethally irradiated gerbils and mice. This renewal time was found to be in excess of 120 hours for the normal Mongolian gerbil in contrast to about 48 hours for the Swiss mouse. In addition, the migration rate was effectively attenuated by sublethal irradiation in both species. This effect was most striking in the case of the gerbil where extrapolation of renewal time data indicates an increase in renewal time of at least 20% over unirradiated controls; this was more than twice the increase demonstrated by the mouse. The observed difference in survival times is consistent with this difference in epthelial renewal rates, and may be a major factor contributing to the long survival time of supralethally irradiated gerbils, particularly when radiation attenuation of migration is considered.

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