Ultrastructural pathological study on skeletal muscle injury in rabbit after a high-dose radiation

Objective To establish a rabbit model of radiation-induced skeletal muscle injury in order to study the ultrastructural pathological changes and underlying mechanism.Methods 28 New Zealand rabbits were randomly divided into 2 groups with 16 rabbits in experimental group and 12 rabbits in control group.The experimental rabbits were irradiated on hip with a single dose of 80 Gy of 9 MeV electrons from a linear accelerator.1 month and 6 months after irradiation the pathological changes were respectively observed under light microscope and electron microscope.Results One month after irradiation,the morphologic changes including degeneration,necrosis of muscle cells,and hemorrhage between the muscle cells were observed under light microscope and the swelling of myofibrillae,blurring of light and shade band,vacuolar degeneration of mitochondria and amorphous areas of necrosis were observed under electron microscope.Six months after irradiation,the morphologic changes of nucleolus chips,fibrous connective tissue,thickening of vascular wall and vascular congestion between the muscle cells and the amorphous areas of necrosis in the experimental group were much more serious than those of 1 month after irradiation.In addition,the myofilaments were lost in degeneration areas and the sarcomere became shorten.Observation with electron microscope showed that the mitochondrial size and its morphological changes were varied and the amounts of collagen between myofibrillaes were increased 6 months after irradiation.Conclusions A rabbit model of high-dose irradiated skeleton muscle injury was successfully established with a single dose of 80 Gy of 9 MeV electrons from a linear accelerator.The degeneration and necrosis of muscle cells may be promoted by mitochondrial and vascular injury,degeneration of vessel and nerve fiber. Key words: Rabbits; Muscle skeletal; Radiation injury; Electron beam; Ultrastructure