NOHARA Ryuji KYOTOUNIV., GRAD. SCH. MED. AS. PROF., 大学院・医学研究科, 講師 (80180769)
MORITANI Toshio KYOTOUNIV., GRAD. SCH. HUM. ENV. ST. A. PROF., 大学院・人間・環境学研究科, 助教授 (90175638)
TSUDA Kinsuke KYOTOUNIV., DEPT. INTEG. HUM. PROF., 総合人間学部, 教授 (10180001)
The present study was designed to determine whether heavy-ion beam irradiation is associated with histochemicalproperties in the skeletal muscle and bone metabolismin young and old SHRSP (stroke prone spontaneously hypertensive rat) rats. For this objective, we carried out following four experiments, 1998〜1999; 1) Effect of heavy-ion irradiation on histochemicalproperty of muscle fibers in young SHRSP rats, 2) Comparative study of histochemicalproperties in skeletal muscle fibers between young and old Wistar rats, 3) Effect of calcium-supplementaionon the myosin heavy chain expression of skeletal muscles in SHR rats following spaceflight, 4) Effects of X-ray irradiation during unweighting on histochemicalproperties of skeletal muscles in rats.
Generally, the highly heavy-ion irradiated group morphometrically displayed a significant alteration in fiber type distribution with an increase of intermediate fibers, and atrophy of SO fibers while those exhibiting little or no change were in ox
idative potential. Irradiated groups, especially three-month-old groups had a tendency to decrease in alpha-gycerophosphate dehydrogenase activity in individual fibers. And, the fermur strength was not changed after heavu-ion irradiation. In third exp., in the soleus muscle, both groups of spaceflightrats regardless of Ca intake increased FOG type fibers (24%) as compared to ground-control. Electrophoretic analysis exhibited higher composition in the type IIx MHC (24〜28%) of the soleus muscles in both spaceflight groups of rats while the ground control rats had 0% type IIx fibers. There was a decrease in type I MHC in both spaceflight groups of rats. The changes in MHC isoforms suggest that microgravity produced the transitionof slow to fast twitch fibers in antigravitymuscles regardless of differences in dietary calcium. Fourth exp. examined that SC and SX groups, after 2 weeks of suspension, an increase in the percentage of intermediatefibers was counterbalancedby a simultaneous significantdecrease in the SO fibers. The SDH activity in the SO fibers in SC and SX rats was significantly increased compared to both of ground groups as well as seen in the α-GPD activity. These findings indicate that the microgravity was more morphometrically and metabolicallyeffective in the muscles than X-ray irradiation. Less