Isometric single-twitch force and intracellular Ca2+ transients were recorded simultaneously, using fura-2, from slow- and fast-twitch muscle fibres of the rat, mouse and Etruscan shrew Suncus etruscus. In the slow-twitch rat soleus, force half-relaxation time was three times longer than the 50 % decay time of the fura-2 signal. In contrast, in the fast-twitch extensor digitorum longus muscles of all three animals, muscle relaxation preceded Ca2+ decay. It is proposed that this surprising property of fast-twitch muscles is due to their pCa­tension curve, which is shifted to the right compared with that of slow-twitch muscle.
Decay of Ca2+ and force transients in fast- and slow-twitch skeletal muscles from the rat, mouse and Etruscan shrew.
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P Wetzel, G Gros; Decay of Ca2+ and force transients in fast- and slow-twitch skeletal muscles from the rat, mouse and Etruscan shrew.. J Exp Biol 1 February 1998; 201 (3): 375–384. doi: https://doi.org/10.1242/jeb.201.3.375
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