Molecular Adaptation of Tropomyosin from Rat Leg Muscle by Running-Training.

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Tropomyosin (Tm) are deeply involved in controls and functions in muscle contraction. Our present project is to know the properties of skeletal Tm isoforms, and to know the molecular adaptation of Tm with running as physical training, using rabbit and rat skeletal muscle. the results were followings. 1) Native forms of Tm consisted nearly of alphabeta-dimeric subunit in soleus and alphaalpha-and alphabeta-subunits, being predominant at alphaalpha-subunit in gastrocnemius. 2) Tension development of the muscle fiber was measured after gastrocnemius and soleus Tms were loaded to glycerinated rabbit psoas muscle fiber, respectively. In contrast to gastrocnemium Tm, soleus one made the fiber decrease the speed of tension development significantly. 3) alphaalpha- And alphabeta-Tms were fractionated by preparative electrophoretic apparatus. The effects of those Tms on acto-HMM ATPase activity were estimated. alphaalpha-Tm inhibited it much more than did alphabeta-Tm. Both Tm exhibited Ca^<2+> … More -sensitivity in actin-activated myosin ATPase activity together with toponin. alphaalpha-Tm gave Ca^<2+>-sensitivity in the ATPase activity than did alphabeta-Tm. 4) Gastrocnemius Tm from endurance-trained rat increased beta-Tm much more than that from control one The Tm from the trained rat made the glycerinated muscle fiber decrease the speed of tension development. 5) The amount of mRNA for beta-subunit of Tm increased in gastrocnemius from endurance training rats.Those results suggest that the properties of muscle contraction such as speed and endurance might be provided with the ratio of alphaalpha- to alphabeta-Tms, because fast twich and slow twich muscles predominate EphiEphi- and EphiEiota-Tms, respectively, in the untrained animals. The training of endurance running increased alphabeta-Tm in the fast twich muscle, which could supply endurance to the muscle. This fact indicates that the fast twich muscle will be able to adapt its properties to endurance running, and that the changes in the ratio of alphaalpha- to alphabeta-Tms are under the genetic control. Less