Pathology of experimental disuse muscular atrophy in rats.

The relationship between structural changes and hyaluronic acid (HA) content in muscular atrophy is unknown. The objective of our study was to conduct multifaceted evaluations of the change in muscle extensibility in muscular atrophy, in terms of morphological aspects as well as from a biochemical viewpoint, including changes in intercellular substances. Using a muscular atrophy model of the soleus muscle in the cast-fixed limbs of Wistar rats, we examined changes in HA accompanying muscular atrophy. Compared with controls, the cast-fixed limbs showed histological evidence of muscular atrophy and electron microscopy indicated destruction of the fasciae. Measurement of the HA level in muscle tissue from cast-fixed rats indicated a reduction in concentration per unit of weight. In contrast, serum HA concentrations increased in the cast-fixed group compared with the control group, suggesting that HA present in the fasciae was released into the blood stream during muscular atrophy.