title: Myosin heavy chains in fibers of TTX-paralyzed rat soleus and medial gastrocnemius muscles.
abstract: 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.
authors.affiliation: Département de Kinésiologie, Université de Montréal, Succursale Centre-ville, Montréal, Québec, Canada H3C 3J7.
authors.forename: B
authors.initials: B
authors.lastname: Cormery
authors.forename: F
authors.initials: F
authors.lastname: Pons
authors.forename: J F
authors.initials: JF
authors.lastname: Marini
authors.forename: P F
authors.initials: PF
authors.lastname: Gardiner
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D005260:Female; D007150:Immunohistochemistry; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation / Q000378:metabolism* / Q000473:pathology; D009133:Muscular Atrophy / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D018995:Myosin Heavy Chains / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D010243:Paralysis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D020033:Protein Isoforms; D013779:Tetrodotoxin; D018995:Myosin Heavy Chains