Decrease in resting calcium and calcium entry associated with slow-to-fast transition in unloaded rat soleus muscle.
Using fura-2 and the manganese quenching technique, we show here that sarcolemmal permeability to cations (SP-Ca) of slow-twitch muscles is greater than that of fast-twitch ones. This appears to be related to a higher expression and/or activity of stretch-activated channels, whereas leak channel activities are similar. During hindlimb suspension (HU), we found highly correlated decreases in SPCa and resting calcium of soleus muscle toward values of extensor digitorum longus (EDL) muscle. This was significant as soon as 3 days of suspension, contrary to soleus muscle caffeine sensitivity and responsiveness that were not modified after this HU period. After 14 days of HU, SP-Ca, resting calcium, and caffeine response of soleus muscle became similar to that normally observed in EDL muscle. These results demonstrate that the correlated decreases in SP-Ca and resting calcium precede most functional changes due to HU. Given the known shortening of HU soleus muscle, we proposed that this could induce a decrease of SP-Ca and a consequent reduction of resting calcium. According to the crucial role of resting cytosolic free calcium in the maintenance and the adaptation of muscle phenotype, our results suggest that slow-to-fast transition of HU soleus muscle is calcium dependent.
Fraysse
Bodvaël
B
Sezione di Farmacologia, Dipartimento Farmaco-Biologico, Università degli Studi di Bari, Via Orabona 4-Campus, 70125, Bari, Italy.
Desaphy
Jean-François
JF
Pierno
Sabata
S
De Luca
Annamaria
A
Liantonio
Antonella
A
Mitolo
Carlo I
CI
Camerino
Diana Conte
DC
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D019417:Hindlimb Suspension; D007700:Kinetics; D008954:Models, Biological; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D009133:Muscular Atrophy / Q000209:etiology; D009928:Organ Specificity; D018408:Patch-Clamp Techniques; D010641:Phenotype; D051381:Rats; D012508:Sarcolemma / Q000378:metabolism
D015220:Calcium Channels; D002118:Calcium