| Research Abstract |
There are many reports that the adaptation of skeletal muscle suitable for the gravity environment shows under a weightless environment. But the report of the effect on the skeletal muscle under a specific environment of estrogen that is the female hormone is few. Then, the purpose of this project was to examine the influence that estrogen exerted on rat's skeletal muscles under a gravity and microgravity environment. First, the adaptation of the skeletal muscle in the microgravity of hindlimb environment was examined. A week of tail suspension resulted in a significant reduction in antigravity slow-twitch soleus muscle weight and total and myofibril protein concentrations, whereas, it did not in fast-twitch extensor digitorum longus (EDL) muscle. Then, the adaptation of the soleus and EDL muscle decided to be examined by using the experiment model that rat's ovary was removed and the circulation of estrogen was decreased. The second experiment gave the endurance run training of seven weeks after ovariectomy under the gravity environment. The increased blood level of the creatine kinase (CK) that was the index of muscle damage after ovariectomy was controlled by endurance training. In soleus muscle, muscle weight per body weight decreased after ovariectomy, and intermediate (INT) fiber composition rate increased after endurance training. On the other hand, a new finding was obtained that FG fiber in EDL muscle increased after ovariectomy, and muscle weight and FOG fiber increased by training. The third experiment gave a tail suspension after ovariectomy. The weight that increased after ovariectomy decreases after tail suspension. In soleus muscle, SO fiber composition rate decreased after the tail suspension. In EDL muscle, another new finding, remarkable decrease of SO fiber after the ovariectomy and an increase of FOG fiber after the ovariectomy and after the tail suspension, were observed.
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