SUMMARYComposition of slow, fast and hybrid fibres of pharyngeal muscles,
associated with pharyngeal movements and regulation, has been rarely
studied. The present study aimed to identify expression of
sarcoplasmic reticulum Ca2+ ATPase (SERCA) and myosin heavy
chain (MHC) and hybrid isoforms in different pharyngeal muscles of
young and aged rats as well as humans. Isoform expression profiles of
SERCA, MHC and hybrid isoforms among six components of pharyngeal
muscle were immunohistochemically evaluated in rat and human. The
result showed that pharyngeal muscles predominantly expressed fast
fibres (SERCA1 and MHCII), whereas expression of slow fibres (SERCA2
and MHCI) was low, but different depending on muscle components. Inner
layer of pharyngeal muscles expressed more SERCA2 and hybrid fibres
than the outer layer. Pharyngeal muscles in aged rats showed increased
hybrid fibers and SERCA2. Human thyropharyngeus also showed a higher
portion of fast fibres compared to cricopharyngeus. Thus, in contrast
to abundance of fast fibres, slow and hybrid fibres are differentially
expressed depending on muscle components and layers as well as aging.
These results lead to further understanding of coordinated regulation
for speech and swallowing. The unique data presented in this study on
SERCA isoform expressions in both rats and human suggest an ability to
handle calcium changes according functional demands.
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