Recovery of the soleus muscle after short- and long-term disuse induced by hindlimb unloading: effects on the electrical properties and myosin heavy chain profile.
The hindlimb unloading (HU) rat is a model of muscle disuse characterized by atrophy and slow-to-fast phenotype transition of the postural muscles, such as the soleus. We previously found that the resting sarcolemmal chloride conductance (gCl) that is typically lower in slow-twitch myofibers than in fast ones increased in soleus fibers following 1 to 3 weeks of HU in accord with the slow-to-fast transition of myosin heavy chain (MHC) isoforms. Nevertheless, the gCl already raised after a 3-day HU, whereas no change in MHC expression was detected. The present work evaluates the ability of soleus muscle to recover on return to normal load after a short (3 days) or long (2 weeks) disuse period. The changes observed after a 2-week HU were slowly reversible, since 3-4 weeks of reloading were needed to completely recover gCl, fiber diameter, MHC expression pattern, as well as the mechanical threshold Rheobase, an index of calcium homeostasis. After 3-day HU, the gCl increased homogeneously in most of the soleus muscle fibers and gCl recovery was rapidly completed after 4-day reloading. These results suggest different induction mechanisms for gCl augmentation after the short and long HU periods, as well as a possible role for gCl in the slow muscle adaptation to disuse.
Desaphy
Jean-François
JF
Unit of Pharmacology, Department of Pharmaco-Biology, Faculty of Pharmacy, University of Bari, Bari, I-70125 Italy.
Pierno
Sabata
S
Liantonio
Antonella
A
De Luca
Annamaria
A
Didonna
M Paola
MP
Frigeri
Antonio
A
Nicchia
G Paola
GP
Svelto
Maria
M
Camerino
Claudia
C
Zallone
Alberta
A
Camerino
Diana Conte
DC
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D018118:Chloride Channels / Q000378:metabolism; D004195:Disease Models, Animal; D019417:Hindlimb Suspension; D006706:Homeostasis / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D009133:Muscular Atrophy / Q000378:metabolism* / Q000503:physiopathology; D018995:Myosin Heavy Chains / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000502:physiology*; D013997:Time Factors; D016474:Weight-Bearing / Q000502:physiology
D018118:Chloride Channels; D018995:Myosin Heavy Chains