The tetanic depression in fast motor units of mammalian skeletal muscle can be evoked by lengthening of one initial interpulse interval

Celichowski, Jan; Dobrzynska, Z; Łochyński, Dawid; Krutki, Piotr

doi:10.1007/s00221-011-2801-1

Cited by 3 publications

(1 citation statement)

References 38 publications

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“…Reductions in contraction duration are also seen with repeated twitch contractions (Krarup 1981;Smith et al 2014). Presently, acceleration in the rate of Ca 2+ uptake into the sarcoplasmic reticulum is the favored mechanism to explain the reductions in contraction duration (Burke 1990;Carp et al 1999;Brown and Loeb 2000;Celichowski et al 2005Celichowski et al , 2011Krutki et al 2006;Tupling 2009;Tsianos and Loeb 2013). Consistent with this attribution, Brown and Loeb (2000) used the assumption that Ca 2+ removal is accelerated during contraction to model activation dynamics for a fast-twitch muscle, and accurately predicted the force profiles seen during actual experiments.…”

Section: Introductionmentioning

confidence: 99%

Can inorganic phosphate explain sag during unfused tetanic contractions of skeletal muscle?

et al. 2016

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We test the hypothesis that cytosolic inorganic phosphate (Pi) can account for the contraction‐induced reductions in twitch duration which impair summation and cause force to decline (sag) during unfused tetanic contractions of fast‐twitch muscle. A five‐state model of crossbridge cycling was used to simulate twitch and unfused tetanic contractions. As Pi concentration ([Pi]) was increased from 0 to 30 mmol·L−1, twitch duration decreased, with progressive reductions in sensitivity to Pi as [Pi] was increased. When unfused tetani were simulated with rising [Pi], sag was most pronounced when initial [Pi] was low, and when the magnitude of [Pi] increase was large. Fast‐twitch extensor digitorum longus (EDL) muscles (sag‐prone, typically low basal [Pi]) and slow‐twitch soleus muscles (sag‐resistant, typically high basal [Pi]) were isolated from 14 female C57BL/6 mice. Muscles were sequentially incubated in solutions containing either glucose or pyruvate to create typical and low Pi environments, respectively. Twitch duration was greater (P < 0.05) in pyruvate than glucose in both muscles. Stimuli applied at intervals approximately three times the time to peak twitch tension resulted in sag of 35.0 ± 3.7% in glucose and 50.5 ± 1.4% in pyruvate in the EDL (pyruvate > glucose; P < 0.05), and 3.9 ± 0.3% in glucose and 37.8 ± 2.7% in pyruvate in the soleus (pyruvate > glucose; P < 0.05). The influence of Pi on crossbridge cycling provides a tenable mechanism for sag. Moreover, the low basal [Pi] in fast‐twitch relative to slow‐twitch muscle has promise as an explanation for the fiber‐type dependency of sag.

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