Metabolic and phenotypic adaptations of diaphragm muscle fibers with inactivation

Wen Zhi Zhan, Hirofumi Miyata, Y. S. Prakash, Gary C. Sieck

Research output: Contribution to journalArticlepeer-review

82 Scopus citations


We hypothesized that metabolic adaptations to muscle inactivity are most pronounced when neurotrophic influence is disrupted. In rat diaphragm muscle (Dia(m)), 2 wk of unilateral denervation or tetrodotoxin nerve blockade resulted in a reduction in succinate dehydrogenase (SDH) activity of type I, IIa, and IIx fibers (~50, 70, and 24%, respectively) and a decrease in SDH variability among fibers (~63%). In contrast, inactivity induced by spinal cord hemisection at C2 (ST) resulted in much less change in SDH activity of type I and IIa fibers (~27 and 24%, respectively) and only an ~30% reduction in SDH variability among fibers. Actomyosin adenosinetriphosphatase (ATPase) activities of type I, IIx, and IIb fibers in denervated and tetrodotoxin-treated Dia(m) were reduced by ~20, 45, and 60%, respectively, and actomyosin ATPase variability among fibers was ~60% lower. In contrast, only actomyosin ATPase activity of type IIb fibers was reduced (~20%) in ST Dia(m). These results suggest that disruption of neurotrophic influence has a greater impact on muscle fiber metabolic properties than inactivity per se.

Original languageEnglish (US)
Pages (from-to)1145-1153
Number of pages9
JournalJournal of applied physiology
Issue number4
StatePublished - Apr 1997


  • actomyosin adenosinetriphosphatase activity
  • denervation
  • muscle fiber
  • spinal hemisection
  • succinate dehydrogenase activity
  • tetrodotoxin

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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