Structural changes in the mouse heart one year after brain exposure to 60Co gamma ray

This study was conducted to investigate the sequential structural changes in the hearts of C3H male mice 1 to 12 months after brain irradiation. A single brain dose of 8 or 20 60Co gamma Gy was given to the animals at 4 months of age. Degenerative changes in the heart occurred, firstly at 6 months after irradiation, and became progressively more severe at 12 months. The cardiac muscle showed areas of focal myofibrillolysis, myofibrillar degeneration with loss of entire myofibrils, the presence of lysosomal-like bodies, and interstitial fibrosis. Coronary artery degeneration was also found at 12 months after irradiation; the major changes included smooth muscle degeneration with fibrosis, and the accumulation of debris and extracellular matrix. Quantitative analysis indicated that the degeneration of the arterial smooth muscle after 20 Gy irradiation (18.9%) was significantly higher than that of the unirradiated control (13.2%), and shammed control (13.3%) groups, p less than 0.05.