Comparison of sarcomere alterations after muscle contraction and tension loading in the rat soleus muscle |
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Authors: | Matsuura Natsue Kawamata Seiichi Ozawa Junya Kai Satoru Sakakima Harutoshi Abiko Sachiko |
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Institution: | Institute of Health Sciences, Faculty of Medicine, Hiroshima University, Hiroshima, Japan |
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Abstract: | Muscle contraction induced by 30 min of continuous nerve stimulation at 50 Hz resulted in sarcomere changes of the soleus
muscle in the rat in our previous study. To further investigate the cause of sarcomere alterations, the sciatic nerve was
electrically stimulated intermittently for 30 min. Nerve stimulation was also conducted after cutting the tendons of the soleus,
gastrocnemius and plantaris muscles in order to prevent imposing tension on these muscles as a result to their own contractions.
In addition, the muscles were pulled by weights via their tendons to load high tension for 30 min without nerve stimulation.
Sarcomere alterations immediately after treatments were quantified by electron microscopy. The percentages of aberrant sarcomere
areas of the soleus muscle were 25.7 ± 16.4% (mean ± SD) in the group of intermittent nerve stimulation with intact tendons
and 21.1 ± 35.4% in the group of tenotomy and continuous nerve stimulation, which were roughly equal to or more severe than
the group of continuous nerve stimulation with intact tendons (18.8 ± 15.8%) in our previous study. Sarcomere alterations
consisted mainly of hypercontraction in these groups. Almost all sarcomere changes in the tension-loaded (pulled) soleus muscles
were scarce myofilaments (1.7 ± 1.0% by 600 g; 4.5 ± 2.9% by 1200 g), and hypercontraction was not observed. These findings
indicate that neither high tension nor a decrease of muscle blood flow during continuous contraction seems to be the primary
cause of sarcomere alterations in the present study. There are probably other causes that produce aberrant sarcomeres. |
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Keywords: | electron microscopy lesion nerve stimulation skeletal muscle tension |
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