RELATIONSHIP BETWEEN OXIDATION OF MYOFIBRILLAR PROTEINS AND CONTRACTILE PROPERTIES IN SOLEUS MUSCLES FROM HYPERTHYROID RAT
reactive oxygen species
specific force reduction
We tested the hypothesis that a force reduction in soleus muscles from hyperthyroid rats would be associated with oxidative modification of myofibrillar proteins. Daily injection of thyroid hormone [3,5,3'-triiodo-L-thyronine (T_3)] for 21 days depressed isometric forces in whole soleus muscle across a range of stimulus frequencies (1, 10, 20, 40, 75 and 100Hz) (P<0.05). In fiber bundles, hyperthyroidism also led to pronounced reductions (P<0.05) in both K^+- and 4-chloro-m-cresol-induced contracture forces. The degrees of the reductions were similar between these two contractures. These reductions in force production were accompanied by a remarkable increment (103% ; P<0.05) in carbonyl groups comprised in myofibrillar proteins. In additional experiments, we have also tested the efficacy of carvedilol, a non-selective β_1-β_2-blocker that possesses anti-oxidative properties. Treatment with carvedilol prevented T_3-induced oxidation of myofibrillar proteins. However, carvedilol did not improve the hyperthyroid-induced reductions in force production. These data suggest that oxidative modification of myofibrillar proteins may not account for the reductions in force production of hyperthyroid rat soleus muscle.
体力科学 : Japanese Journal of Physical Fitness and Sports Medicine
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Graduate School of Integrated Arts and Sciences