We examined the functional properties of the Ca²⁺ uptake, the Ca²⁺ leakage and the Ca²⁺ release channel of the sarcoplasmic reticulum (SR) in skeletal muscle fibers from the suspended hindlimbs of rats. Adult male Wistar rats were obtained and randomly divided into a hindlimb suspension (HS) group and a control group. On the 14th day of HS, animals in both groups were anesthetized and the soleus muscle was immediately removed. In the SR of suspended soleus muscle fibers, the capacity of Ca²⁺ uptake was higher than that in the control muscles. The passive Ca²⁺ leakage from the SR in soleus was apparently increased following HS. Ryanodine treatment reduced the Ca²⁺ uptake capacity of the SR in the control muscle fibers. Following HS, the depression of Ca²⁺ uptake of the SR by the treatment of ryanodine was smaller than that in the control SR. The functional properties of the SR were qualitatively altered during atrophy. These observations suggest that the contractile properties of skeletal muscles may be related to muscular Ca²⁺ movements involved in the SR function.

DESCENTE SPORTS SCIENCE Vol.19/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE