Key result
TTX-induced paralysis increases hybrid muscle fibers co-expressing developmental myosin heavy chain isoforms.
Why the study?
The effects of TTX-induced paralysis on the expression of multiple myosin heavy chain isoforms in rat soleus and medial gastrocnemius muscles were analyzed to understand muscle fiber changes.
TTX-induced muscle paralysis leads to an increase in hybrid muscle fibers co-expressing multiple myosin heavy chain isoforms, notably the developmental isoform.
The expression of five myosin heavy chain (MHC) isoforms was analyzed in the rat soleus (Sol) and the deep and superficial medial gastrocnemius (dGM, sGM) muscle after 2 and 4 wk of TTX paralysis by using immunohistochemical techniques. In Sol, after 4 wk of paralysis, fibers containing type I MHC were either pure type I (14%) or also contained developmental (D; 76%), IIa (26%), or IIx (18%) MHC. Values for corresponding fibers in dGM were 8.5, 65, 38, and 22%. Also, by 4 wk an increase was seen in the proportions of fibers expressing IIa MHC in Sol (from 16 to 38%) and dGM (from 24 to 74%). In a region of sGM in control muscles containing pure IIb fibers, a major proportion (86%) remained pure after 4 wk of paralysis, with the remainder coexpressing IIb and IIx. The results indicate that TTX-induced muscle paralysis results in an increase in fibers containing multiple MHC isoforms and that the D isoform appears in a major proportion of these hybrid fibers.
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Cormery et al. (2000) studied TTX paralysis (animal model). TTX paralysis vs. Control muscles was evaluated on Expression of five myosin heavy chain (MHC) isoforms. TTX-induced muscle paralysis in rats resulted in an increase in fibers containing multiple MHC isoforms, with the developmental isoform appearing in a major proportion of these hybrid fibers.
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