Key result
Hindlimb immobilization for 1 week significantly shifted the MHC mRNA profile toward faster isoforms, including a 24-fold upregulation of type IIx in the soleus (P<0.005).
Effect estimate: 24-fold increase (type IIx in soleus)
p-value: p=<0.005
Immobilization of skeletal muscle in rats shifts the myosin heavy chain mRNA profile toward faster isoforms.
Short immobilization may promote faster muscle isoforms; leaves open human translation and cardiovascular relevance.
Jänkälä, Heidi, Veli-Pekka Harjola, Niels Erik Petersen, and Matti Härkönen. Myosin heavy chain mRNA transform to faster isoforms in immobilized skeletal muscle: a quantitative PCR study. J. Appl. Physiol. 82(3): 977–982, 1997.—A quantitative polymerase chain reaction (PCR) method was used to measure the quantities of type I, IIa, IIx, and IIb myosin heavy chain (MHC) mRNA in total RNA preparations of the soleus, gastrocnemius, and plantaris muscles of normal and hindlimb-immobilized rats. Type IIx and even type IIb MHC mRNA were demonstrated at extremely low levels in normal soleus, 2.1 ± 0.4 × 10 5 and 5.0 ± 0.2 × 10 5 molecules of mRNA per microgram total RNA, respectively. Immobilization for 1 wk significantly altered the gene expression of MHC isoforms. In soleus, both type IIx and IIb MHC genes became significantly upregulated, 24-fold ( P < 0.005) and 2.6-fold ( P < 0.05), respectively. In gastrocnemius, the level of type IIa MHC mRNA decreased by 51% ( P < 0.01) and the level of type IIx MHC mRNA increased by 140% ( P < 0.05). In plantaris, the level of type IIa MHC mRNA decreased by 58% ( P < 0.005). In conclusion, immobilization changed the MHC mRNA profile in three different types of skeletal muscle toward faster isoforms. The quantitative results permit reliable evaluation of changes in mRNA levels.
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Jänkälä et al. (1997) studied Hindlimb immobilization in rats. Hindlimb immobilization vs. Normal rats was evaluated on Quantities of type I, IIa, IIx, and IIb myosin heavy chain (MHC) mRNA (24-fold increase (type IIx in soleus), p=<0.005). Hindlimb immobilization for 1 week significantly shifted the MHC mRNA profile toward faster isoforms, including a 24-fold upregulation of type IIx in the soleus (P<0.005).
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