Reversible injury after mild hyperthermia.

Skin contraction and leg contracture resulted from immersion of mice legs in a water bath at temperatures of 42.5 degrees to 43.7 degrees C for 45 to 90 minutes. The maximum contracture was observed between 5 and 15 days after treatment, but little damage remained after about 30 days. After healing of the early tissue damage, there was no progression of residual damage in skin up to 490 days after treatment. In contrast, radiation-induced contracture develops rapidly after 14 days, and may continue to progress for 100 days or more. In the present studies, leg contracture could be attributed primarily to injury in the skin, because skinning the legs before measuring eliminated most of the contracture. Temperature differences between subcutaneous tissue and deep muscle were not consistently observed or statistically significant, and probably made little or no contribution to the difference in thermal response of these tissues.