Levels of Myosin Heavy Chain
mRNA Transcripts and Content of Protein Isoforms in the Slow
Soleus Muscle of 7 month-old Rats with Altered Thyroid Status
A. VADÁSZOVÁ, S. HUDECOVÁ1, O.
KRIŽANOVÁ1, T. SOUKUP
Institute of Physiology, Czech Academy of Sciences, Prague,
Czech Republic and 1Institute
of Molecular Physiology and Genetics, Slovak Academy of
Sciences, Bratislava, Slovak Republic
Received September 15, 2005
Accepted December 22, 2005
Summary
Skeletal muscles of small rodents contain four main fiber types,
namely type 1, 2A, 2X/D and 2B fibers containing myosin heavy
chain (MyHC) 1, 2a, 2x/d and 2b isoforms. Each of these MyHC
isoforms is the product of a distinct gene and their expression
is believed to be primarily transcriptionally controlled. In
most rat muscles, messenger RNA (mRNA) transcripts for MyHC1,
2a, 2x/d and 2b and their corresponding protein products were
found with the exception of the soleus muscle, where typically
only MyHC1 and 2a transcripts and protein isoforms were
demonstrated under normal conditions. Here we show the
expression of all four MyHC1, 2a, 2x/d and 2b mRNA transcripts
in the soleus muscle under normal conditions in euthyroid, as
well as in experimental hypothyroid and hyperthyroid (with the
exception of 2b MyHC transcript) 7-month-old female inbred Lewis
rats. This is not matched, however, by the appearance of
corresponding four isoforms, as we have found that 2x/d and 2b
protein isoforms are not present at levels detectable by
SDS-PAGE. We also show that the chronic hypothyroid and
hyperthyroid status affects the expression of MyHC isoforms both
at the mRNA and protein levels.
Key words
Rat soleus muscle • Myosin heavy chains • mRNA transcripts •
Thyroid hormones • SDS-PAGE and RT-PCR
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