Early and late radiation reactions in mouse feet.

The relationship between early and late radiation damage has been analysed by comparing the early skin reaction (desquamation in the first month) with the late foot deformity seen at 6 months, for mice from a wide variety of different fractionation experiments. A close correlation was observed between the early and late reactions in each experiment and the relationship was the same for all the experiments except for 17-64 fractions given over a short time. The fractionation schemes included single doses and 2-64 fractions, and the overall times ranged from 1 day to 6 months. This close correlation for such a wide variety of treatments suggests that the two end points are not necessarily independent responses of different tissues and that late damage in the mouse foot can result secondarily from depletion of the basal layer of the epidermis. Late foot deformity is therefore not a reliable model for the response of a slowly proliferating tissue.