Effect of DMTU Pretreatment on Ultrastructural Changes in Tibialis Anterior Muscles and Soleus Muscles of Rats after Irradiation

Paik, Doo Jin; Chung, Ho Sam; Lee, Koon Ja; So, Byung Jo

Abstract

Free radicals, formed by ionization of water molecules, cause significant increase of morbidity and mortality in irradiated humans. The skeletal muscle is relatively radio-resistant because of its few content of proliferating cells. But the incidence and severity of muscular damage depends on the dose of radiation and time lapse. This study is aimed to investigate the ultrastructural changes and the effect of radiation and DMTU on two muscles, the tibialis anterior and the soleus muscle; the former is dominantly composed of white muscles while the latter is mainly composed of red muscles. Each muscle also show differences in energy production and distribution of capillaries. The male Sprague-Dawley rats weighing from 200 g to 250 g were used as experimental animals. Under urethane(1.15 g/kg, i.p.) anesthesia, 30Gy irradiation to lower extremities with PICKER-C9 cobalt 60 teletherapy unit was done. DMTU(500 mg/kg, i.p.) was administered 1 hour prior to irradiation. The animals were sacrificed 1 day, 3 days, 7 days, 2 weeks, and 4 weeks after irradiation. The muscular tissues in midbelly of tibialis anterior and the soleus muscles were obtained and sliced into 2 mm in length, 1 mm in width and thickness. The specimens were prepared by routine method for electron microscopy. The results obtained were as follows: 1. Widening of interfibrillar space, mitochondrial changes of eletron-lucent matrix and dilated cristae, and cisternal dilatation of sarcoplasmic reticulum were observed in both muscles after irradiation. More severe ultrastructural changes with time course were observed by 2 weeks. But those were recovered to normal at 4 weeks after irradiation. 2. More severe ultrastructural changes in soleus were observed 1 and 3 days after irradiation, and in tibialis anterior at 7 days and 2 weeks. Those findings were associated with reduction of glycogen contents in the myofibers of both muscles. 3. Widening of intermyofibrillar space, mitochondrial changes of electron-lucent matrix and indistinct cristae, and cisternal dilatation of sarcoplasmic reticulum were observed in both muscles after DMTU treatment. 4. Pretreatment of DMTU attenuated the ultrastructural changes induced by irradiation. Those were recoved normally by 2 weeks. Consequently, DMTU attenuates the ultrastructural changes in tibialis anterior and soleus muscle after irradiation. The more severe morphological changes in soleus muscle at 1 day and 3 days, and in tibialis anterior at 7 days and 2 weeks after irradiation are associated with the reduction of glycogen contents.