title: Adaptation of muscle fibre types and capillary network to acute denervation and shortlasting reinnervation.
abstract: We postulated that, in rat extensor digitorum longus muscle (EDL), the length of capillaries per fibre surface area (Lcap/Sfib) and per fibre volume (Lcap/Vfib) could reflect fibre-type transformations accompanied by changes in oxidative metabolic profile and selective fibre-type atrophy. We excised rat EDL muscle 2 weeks after the sciatic nerve was cut (acute denervation; DEDL) and 4 weeks after the nerve was crushed (early reinnervation; REDL) and characterised muscle fibre-type transformation by the expression of myosin heavy-chain isoforms and by succinate dehydrogenase (SDH) and nicotinoamide adenine dinucleotide-tetrazolium reductase (NADH-TR) reactions. The numerical percentage (N/N) and area percentage (A/A) of pure and hybrid fibres and their diameter were determined, as was the A/A of SDH- and NADH-TR-positive fibres. The length of capillaries per fibre length (Lcap/Lfib), Lcap/Sfib and Lcap/Vfib were estimated in REDL and Lcap/Vfib in DEDL. In DEDL, the type 2x and 2b fibres evidently atrophied, with the N/N of type 2x fibres being lower and that of hybrid fibres higher. In REDL, the N/N of hybrid fibres was even higher, consequent to a lower N/N of type 2b fibres; however, fibre diameters approached values of the control EDL. Compared with control EDL, denervated and reinnervated muscles exhibited a higher A/A of oxidative fibres. This is probably the result of fibre-type transformation and selective fibre atrophy. We conclude that capillary length does not change during acute denervation and early reinnervation. The obtained higher values of Lcap/Sfib and Lcap/Vfib are related to changes in muscle fibre cross-sectional area.
authors.affiliation: Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Ljubljana, 1000, Slovenia.
authors.forename: Vita
authors.initials: V
authors.lastname: Cebasek
authors.forename: Lucie
authors.initials: L
authors.lastname: Kubínová
authors.forename: Jirí
authors.initials: J
authors.lastname: Janácek
authors.forename: Samo
authors.initials: S
authors.lastname: Ribaric
authors.forename: Ida
authors.initials: I
authors.lastname: Erzen
mesh_terms: D000208:Acute Disease; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D002196:Capillaries / Q000166:cytology* / Q000502:physiology; D048429:Cell Size; D003714:Denervation; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation / Q000503:physiopathology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology; D010085:Oxidative Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D020426:Sciatic Neuropathy / Q000503:physiopathology; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013997:Time Factors