Adenosinetriphosphatase (ATPase) activity of myofibrils prepared from pre-rigor and from rigor rat skeletal muscle

1991 ◽  
Vol 19 (1) ◽  
pp. 38S-38S
Author(s):  
WILLIAM J. REVILLE ◽  
GERARDENE A. MEADE
Keyword(s):  
Skeletal Muscle ◽  
Atpase Activity ◽  
Rat Skeletal Muscle

Fiber-specific regulation of Ca(2+)-ATPase isoform expression by thyroid hormone in rat skeletal muscle

1996 ◽  
Vol 271 (6) ◽  
pp. C1908-C1919 ◽  
Author(s):  
C. G. van der Linden ◽  
W. S. Simonides ◽  
A. Muller ◽  
W. J. van der Laarse ◽  
J. L. Vermeulen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Thyroid Hormone ◽  
Atpase Activity ◽  
Cross Sections ◽  
Time Course ◽  
Myosin Heavy Chain Isoforms ◽  
Rat Skeletal Muscle ◽  
Mhc I ◽  
Isoform Expression ◽  
Specific Regulation

We studied the effect of thyroid hormone (3,5,3'-triiodo-L-thyronine, T3) on the expression of sarcoplasmic reticulum (SR) fast- and slow-type Ca(2+)-ATPase isoforms, SERCA1 and SERCA2a, respectively, and total SR Ca(2+)-ATPase activity in rat skeletal muscle. Cross sections and homogenates of soleus and extensor digitorum longus muscles from hypo-, eu-, and hyperthyroid rats were examined, and expression of Ca(2+)-ATPase isoforms in individual fibers was compared with expression of fast (MHC II) and slow (MHC I) myosin heavy chain isoforms. In both muscles, T3 induced a coordinated and full conversion to a fast-twitch phenotype in one-half of the fibers that were slow twitch in the absence of T3. The conversion was partial in the other one-half of the fibers, giving rise to a mixed phenotype. The stimulation by T3 of total SERCA expression in all fibers was reflected by increased SR Ca(2+)-ATPase activity. The time course of the T3-induced changes of SERCA isoform expression was examined 1-14 days after the start of daily T3 treatment of euthyroid rats. SERCA1 expression was stimulated by T3 at a pretranslational level in all fibers. SERCA2a mRNA expression was transiently stimulated and disappeared in a subset of fibers. In these fibers SR Ca(2+)-ATPase activity was high because of high SERCA1 protein levels. These data suggest that the ultimate downregulation of SERCA2a expression, which is always associated with high SR Ca(2+)-ATPase activities, occurs at a pretranslational level.

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