title: Metabolic and phenotypic adaptations of diaphragm muscle fibers with inactivation.
abstract: 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 (approximately 50, 70, and 24%, respectively) and a decrease in SDH variability among fibers (approximately 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 (approximately 27 and 24%, respectively) and only an approximately 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 approximately 20, 45, and 60%, respectively, and actomyosin ATPase variability among fibers was approximately 60% lower. In contrast, only actomyosin ATPase activity of type IIb fibers was reduced (approximately 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.
authors.affiliation: Department of Anesthesiology, Mayo Foundation, Rochester, Minnesota 55905, USA.
authors.forename: W Z
authors.initials: WZ
authors.lastname: Zhan
authors.forename: H
authors.initials: H
authors.lastname: Miyata
authors.forename: Y S
authors.initials: YS
authors.lastname: Prakash
authors.forename: G C
authors.initials: GC
authors.lastname: Sieck
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D003964:Diaphragm / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009121:Muscle Denervation; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology / Q000502:physiology; D018995:Myosin Heavy Chains / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D013779:Tetrodotoxin; D013385:Succinate Dehydrogenase; D018995:Myosin Heavy Chains; D009218:Myosins