Locke M, Atkinson B G, Tanguay R M, Noble E G
Faculty of Kinesiology, University of Western Ontario, London, Canada.
Am J Physiol. 1994 May;266(5 Pt 1):C1240-6. doi: 10.1152/ajpcell.1994.266.5.C1240.
Heat-shock protein 72 (HSP72), the inducible isoform of the HSP70 family, is constitutively expressed in rat hindlimb muscles in proportion to the content of type I muscle fibers. To determine whether this relationship was maintained after fiber transformation, male Sprague-Dawley rats were treated with 3,5,3'-triiodo-DL-thyronine (T3) for 40 days or underwent surgical removal of the left gastrocnemius muscle, after which the left plantaris muscle was allowed to hypertrophy for 30 days. Hypertrophied plantaris muscles exhibited an increased number of type I fibers, type I myosin heavy-chain (MHC) protein, and HSP72 content compared with contralateral muscles. Soleus muscles from rats administered T3 exhibited an increased number of type II fibers, citrate synthase activity, and decreased HSP72 content compared with soleus muscles from controls. These results indicate that the relationship between HSP72 content and type I muscle fiber-MHC composition is maintained when muscles undergo fiber transformation and substantiate that HSP72 content in rat skeletal muscle is not directly linked to a muscle's oxidative capacity.
热休克蛋白72（HSP72）是HSP70家族的诱导型异构体，在大鼠后肢肌肉中组成性表达，其表达量与I型肌纤维的含量成正比。为了确定在纤维类型转变后这种关系是否依然存在，对雄性斯普拉格-道利大鼠用3,5,3'-三碘-DL-甲状腺原氨酸（T3）处理40天，或手术切除左侧腓肠肌，之后让左侧跖肌肥大30天。与对侧肌肉相比，肥大的跖肌I型纤维数量、I型肌球蛋白重链（MHC）蛋白和HSP72含量均增加。与对照组大鼠的比目鱼肌相比，给予T3的大鼠的比目鱼肌II型纤维数量增加、柠檬酸合酶活性增强且HSP72含量降低。这些结果表明，当肌肉发生纤维类型转变时，HSP72含量与I型肌纤维-MHC组成之间的关系依然存在，并且证实大鼠骨骼肌中HSP72含量与肌肉的氧化能力没有直接关联。
