Fiber type-related changes in rat skeletal muscle calcium homeostasis during aging and restoration by growth hormone.
The mechanisms by which aging induces muscle impairment are not well understood yet. We studied the impact of aging on Ca2+ homeostasis in the slow-twitch soleus and the fast-twitch extensor digitorum longus (EDL) muscles of aged rats by using the fura-2 fluorescent probe. In both muscles aging increases the resting cytosolic calcium concentration ([Ca2+]i). This effect was independent on calcium influx since a reduced resting permeability of sarcolemma to divalent cations was observed in aged muscles likely due to a reduced activity of leak channels. Importantly the effects of aging on resting [Ca2+]i, fiber diameter, mechanical threshold and sarcolemmal resting conductances were less pronounced in the soleus muscle, suggesting that muscle impairment may be less dependent on [Ca2+]i in the slow-twitch muscle. The treatment of aged rats with growth hormone restored the resting [Ca2+]i toward adult values in both muscles. Thus, an increase of resting [Ca2+]i may contribute to muscle weakness associated with aging and may be considered for developing new therapeutic strategies in the elderly.
Fraysse
Bodvael
B
Division of Pharmacology, Department of Pharmaco-Biology, Faculty of Pharmacy, University of Bari, Bari I-70125, Italy.
Desaphy
Jean-François
JF
Rolland
Jean-François
JF
Pierno
Sabata
S
Liantonio
Antonella
A
Giannuzzi
Viviana
V
Camerino
Claudia
C
Didonna
M Paola
MP
Cocchi
Daniela
D
De Luca
Annamaria
A
Conte Camerino
Diana
D
D000375:Aging; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016257:Fura-2 / Q000378:metabolism; D013006:Growth Hormone / Q000494:pharmacology*; D006706:Homeostasis / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010539:Permeability; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000378:metabolism
D013006:Growth Hormone; D002118:Calcium; D016257:Fura-2