Differential radiation response amongst proliferating epithelial cells.

Tissue irradiation results in both reproductive and histologically evident cell death. The correlation between these is poor. Irrespective of dose and fraction sterilized, many cells behave as if unirradiated (cell cycle and maturation activity). The fraction of histologically observable dead cells is usually less than 0.1, with most in the intestine being positioned in the presumptive stem cell region. The data strongly suggest different epithelial sub-populations with differing radioresponses. These may be the stem and differentiated proliferative cells.