Cross-bridge cycling kinetics in human muscle fibers expressing different MHC isoforms

P. C. Geiger, M. J. Cody, D. N. Proctor, Gary C Sieck

Research output: Contribution to journalArticle

Abstract

A correlation exists between maximum unloaded shortening velocity (Vo) and myosin heavy chain (MHC) isoform expression in muscle fibers. The present study examined the association between MHC isoform expression and estimates of cross-bridge cycling kinetics in single human vastus lateralis muscle fibers. MHC isoform expression was determined by SDS PAGE. 80% of all fibers singularly expressed MHC isoforms (MHCSlow 35%; MHC2A 38%; MHC2X 7%), while 18% co-expressed MHC2A and MHC2X isoforms, and 2% co-expressed MHC2A and MHCSlow isoforms. Mechanical measurements in single triton-X permeabilized fibers during maximum Ca2+ activation (pCa 4.0) at 15°C included: Vo measured using the "slack" test; rate of force redevelopment (k) after a rapid release (15% Lo) and restretch; and ratio of stiffness (0.2%Lo length oscillations at 1kHz) during maximal activation to rigor (αfs). From these measures, apparent forward (fapp) and reverse (gapp) rate constants for cross-bridge cycling were estimated (k=fapp+gapp and αfs=fapp/fapp+gapp). Both Vo and k were slower in fibers expressing the MHCSlow isoform compared to fibers expressing fast MHC isoforms, while αfs was comparable across fiber types. These results indicate that both fapp and gapp are slower in human fibers expressing the MHCSlow isoform compared to fibers expressing fast MHC isoforms. The impact of MHC isoform co-expression could only be evaluated in fibers co-expressing MHC2A and MHC2X isoforms where no effect on cross-bridge cycling kinetics was observed.

Original languageEnglish (US)
JournalFASEB Journal
Volume12
Issue number5
StatePublished - Mar 20 1998

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Myosin Heavy Chains
myosin heavy chains
muscle fibers
Muscle
Protein Isoforms
dietary fiber
kinetics
Muscles
Kinetics
Fibers
Chemical activation
shortenings
oscillation
Quadriceps Muscle
calcium
Polyacrylamide Gel Electrophoresis
Rate constants
Stiffness
Association reactions

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology

Cite this

Geiger, P. C., Cody, M. J., Proctor, D. N., & Sieck, G. C. (1998). Cross-bridge cycling kinetics in human muscle fibers expressing different MHC isoforms. FASEB Journal, 12(5).

Cross-bridge cycling kinetics in human muscle fibers expressing different MHC isoforms. / Geiger, P. C.; Cody, M. J.; Proctor, D. N.; Sieck, Gary C.

In: FASEB Journal, Vol. 12, No. 5, 20.03.1998.

Research output: Contribution to journalArticle

Geiger, PC, Cody, MJ, Proctor, DN & Sieck, GC 1998, 'Cross-bridge cycling kinetics in human muscle fibers expressing different MHC isoforms', FASEB Journal, vol. 12, no. 5.
Geiger, P. C. ; Cody, M. J. ; Proctor, D. N. ; Sieck, Gary C. / Cross-bridge cycling kinetics in human muscle fibers expressing different MHC isoforms. In: FASEB Journal. 1998 ; Vol. 12, No. 5.
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