A quantitative study of chronic radiation injury on striated muscle of mice

Chronic radiation injury on striated muscle of mice was quantitatively studied by radiotracers, sup(99m)Tc-red blood cell (sup(99m)Tc-RBC), sup(99m)Tc-human serum albumin (sup(99m)Tc-HSA) and 201Tl-chloride. Left lower extremity of each mouse was locally irradiated with 3,000 R. Microscopic examinations revealed histological changes indicating chronic radiation injury on the 112th day after irradiation. Vascular volume measured by sup(99m)Tc-RBC was increased even on the 1st day and reached a peak on the 14th day. The mean vascular volume reached a second peak on the 112th day. Vascular permeability to HSA increased even on the 1st day and showed also a biphasic response to reach the highest second peak on the 112th day. 201Tc-extraction ratio was low on the 3rd and 7th days. This result in combination with increased vascular volume may indicate the presence of direct muscular injury on early days after irradiation. 201Tc-extraction ratio became lower again on the 56th and 112th days accompanying with an increased vascular volume. Thus, these hemodynamic indicators could be useful means for detection of chronic radiation injury on irradiated muscle. (author)