title: MHC isoform composition and Ca(2+)- or Sr(2+)-activation properties of rat skeletal muscle fibers.
abstract: Chemically skinned single fibers from adult rat skeletal muscles were used to test the hypothesis that, in mammalian muscle fibers, myosin heavy chain (MHC) isoform expression and Ca(2+)- or Sr(2+)-activation characteristics are only partly correlated. The fibers were first activated in Ca(2+)- or Sr(2+)-buffered solutions under near-physiological conditions, and then their MHC isoform composition was determined electrophoretically. Fibers expressing only the MHC I isoform could be appropriately identified on the basis of either the Ca(2+)- or Sr(2+)-activation characteristics or the MHC isoform composition. Fibers expressing one or a combination of fast MHC isoforms displayed no significant differences in their Ca(2+)- or Sr(2+)-activation properties; therefore, their MHC isoform composition could not be predicted from their Ca(2+)- or Sr(2+)-activation characteristics. A large proportion of fibers expressing both fast- and slow-twitch MHC isoforms displayed Ca(2+)- or Sr(2+)-activation properties that were not consistent with their MHC isoform composition; thus both fiber-typing methods were needed to fully characterize such fibers. These data show that, in rat skeletal muscles, the extent of correlation between MHC isoform expression and Ca(2+)- or Sr(2+)-activation characteristics is fiber-type dependent.
authors.affiliation: School of Life Sciences and Technology, Victoria University of Technology, Melbourne, Victoria 8001, Australia.
authors.forename: S K
authors.initials: SK
authors.lastname: Bortolotto
authors.forename: M
authors.initials: M
authors.lastname: Cellini
authors.forename: D G
authors.initials: DG
authors.lastname: Stephenson
authors.forename: G M
authors.initials: GM
authors.lastname: Stephenson
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003964:Diaphragm / Q000201:enzymology / Q000502:physiology; D006614:Hindlimb; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000201:enzymology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013324:Strontium / Q000494:pharmacology*
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains; D002118:Calcium; D013324:Strontium