Late Effects in Mouse Heart after⁶⁰Co γ-irradiation of the Brain: An Ultrastructural Study

Abstract

A single dose of 8 or 20 Gy 60Co gamma-rays was given to C3H male mice at 4 months of age. Degenerative changes in the cardiac muscle due to brain irradiation were observed first at 6 months after irradiation, and became progressively more severe at 12-24 months. The changes seen at the ultrastructural level included myofibrillolysis, the presence of lysosomal-like bodies and interstitial fibrosis. Ultrastructural changes in the control cardiac muscle throughout the experimental period were monitored and only minor aging changes were noted. The coronary arteries of control mice began to show a slight amount of smooth muscle degeneration and fibrosis 1 year into the experiment. At 18 months the lesions became more severe, and at 24 months there was relatively less distinction between the control and the 20 Gy treated group. Degenerative changes in the coronary arteries were noticed at 6 months after irradiation, and became progressively more severe at later times (12-24 months). The major changes included smooth muscle degeneration with fibrosis and the accumulation of debris and extracellular matrix. At 18 months the medial smooth muscle showed severe damage, with accumulations of matrix material and debris. There was additional fibrosis in the adventitial layer. There were few additional changes at 24 months after 20 Gy irradiation. Quantitative analyses indicated that the average fractional volumes of degenerated smooth muscle cells were 13, 27 and 39% in the unirradiated group at 12, 18 and 24 months, respectively, and 13 and 29% in the sham-irradiated group at 12 and 18 months into the experiment, respectively. These percentages were 12, 32 and 49% (P less than 0.05) after 8 Gy irradiation, and 19% (P less than 0.05), 46% (P less than 0.01), and 42% after 20 Gy irradiation, respectively.

Irradiation of the kidneys causes pathologic remodeling in the nontargeted heart: A role for the immune system

“…49 Irradiation of the brain with 20 Gy of gamma rays resulted in degenerative changes in the coronary arteries after 180-720 months. 50 In another study with densely ionizing 56 Fe ions, irradiation of mouse orbital regions with 0.1 or 0.2 Gy of 56 Fe ions resulted in degenerative changes in coronary arteries. 51 Taken together, these studies suggest that both sparsely ionizing radiation (X-or gamma rays) and densely ionizing radiation (e.g., Ti or Fe ions) of individual organs exerts an effect on multiple nontargeted organs, including the heart.…”

“…Irradiation of the rat head with densely ionizing 1100 MeV titanium ions elicited altered protein expression in the nontargeted liver many months postirradiation 49 . Irradiation of the brain with 20 Gy of gamma rays resulted in degenerative changes in the coronary arteries after 180‐720 months 50 . In another study with densely ionizing 56 Fe ions, irradiation of mouse orbital regions with 0.1 or 0.2 Gy of 56 Fe ions resulted in degenerative changes in coronary arteries 51 .…”