Calcineurin-NFAT signaling and neurotrophins control transformation of myosin heavy chain isoforms in rat soleus muscle in response to aerobic treadmill training

This study elucidated the role of can-nfat signaling and neurotrophins on the transformation of myosin heavy chain isoforms in the rat soleus muscle fiber following aerobic exer-cise training. to do so,we examined the content and distribution of myosin heavy chain (myhc) isoforms in the rat soleus mus-cle fiber,the activity of can and expression of nfatc1 in these fibers,and changes in the expression of nerve growth factor (ngf),brain-derived neurotrophic factor (bdnf) and neutro-phin-3 (nt-3) in the soleus and striatum following high-and medium-intensity aerobic treadmill training. specific pathogen-free 2 month old male sprague-dawley (sd) rats were randomly divided into three groups: control group (con,n = 8),moderate-intensity aerobic exercise group (m-ex,n = 8) and high-intensity aerobic exercise group (h-ex,n = 8). we used atpase staining to identify the muscle fiber type i and ii,sds-page to separate and analyze the isoforms myhci,myhciia,myhciib and myhciix,and performed western blots to deter-mine the expression of nfatc1,ngf,bdnf and nt-3. can activity was measured using a colorimetric assay. in the soleus muscle,8 weeks of moderate-intensity exercise can induce transformation of myhc iia and myhc iib to myhc iix and myhc i (p < 0.01),while high-intensity treadmill exercise can induce transform myhc iix to myhc iib,myhc iia and myhc i (p < 0.01). in comparison to the control group,can activity and nfatcl protein level were significantly increased in both the m-ex and h-ex groups (p < 0.05,p < 0.01),with a more pronounced upregulation in the m-ex group (p < 0.05). eight weeks of moderate- and high-intensity aerobic exercise induced the expression of ngf,bdnf and nt-3 in the soleus muscle and the striatum (p < 0.01),with the most significant increase in the h-ex group (p < 0.01). in the rat soleus muscle,(1) can–nfatcl signaling contributes to the conversion of myhc i isoform in response to moderate-intensity exercise; (2) neurotrophins ngf,bdnf and nt-3 might play a role in the conversion of myhc ii isoform in response to high-intensity treadmill exercise. ©journal of sports science and medicine.