Response of previously irradiated mouse skin to a second course of irradiation: early skin reaction and skin shrinkage

Abstract

The responses of previously irradiated hind legs of mice to second courses of gamma ray irradiation were studied using early skin reaction and skin shrinkage as end points. The hind legs of mice were treated with various doses in single and multifractionated irradiation at one-day intervals, 12 months after a variety of doses in various treatment schedules and in a single exposure, respectively. The re-irradiated skin was relatively radioresistant compared to the previously non-irradiated skin, depending on the skin site used and the end point used to evaluate the skin's radiation sensitivity. Early skin reactions that occurred after test doses administered to pre-irradiated skin developed sooner, and remained longer, than skin reactions that developed in the previously non-irradiated controls, regardless of treatment regimens. The degree of early skin reaction to the test dose was greater in the pre-irradiated skin, when the test dose was relatively small, and lower, when the test dose was relatively large, regardless of treatment regimens with one exception: the ventral aspect of the mouse's hind leg responded more to multifractionated test doses in the pre-irradiated skin. The degree of skin shrinkage, assessed 50–60 days after the test dose, was less in the pre-irradiated skin than in the previously non-treated controls, for each dose in each test treatment schedule. The amount of skin shrinkage, resulting from a given test dose (25 or 40 Gy), decreased with increasing dose during the first course of each treatment schedule. The degree of skin shrinkage caused by the first and second exposure, however, increased when the total dose of the first course and the test exposure was increased.