scholarly journals Comparison of regulated passive membrane conductance in action potential–firing fast- and slow-twitch muscle

2009 ◽  
Vol 134 (4) ◽  
pp. 323-337 ◽  
Author(s):  
Thomas Holm Pedersen ◽  
William Alexander Macdonald ◽  
Frank Vincenzo de Paoli ◽  
Iman Singh Gurung ◽  
Ole Bækgaard Nielsen
Keyword(s):  
Action Potential ◽  
Muscle Fibers ◽  
Membrane Conductance ◽  
Fiber Types ◽  
Channel Inhibition ◽  
Slow Twitch Muscle ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch ◽  
Passive Membrane

In several pathological and experimental conditions, the passive membrane conductance of muscle fibers (Gm) and their excitability are inversely related. Despite this capacity of Gm to determine muscle excitability, its regulation in active muscle fibers is largely unexplored. In this issue, our previous study (Pedersen et al. 2009. J. Gen. Physiol. doi:10.1085/jgp.200910291) established a technique with which biphasic regulation of Gm in action potential (AP)-firing fast-twitch fibers of rat extensor digitorum longus muscles was identified and characterized with temporal resolution of seconds. This showed that AP firing initially reduced Gm via ClC-1 channel inhibition but after ∼1,800 APs, Gm rose substantially, causing AP excitation failure. This late increase of Gm reflected activation of ClC-1 and KATP channels. The present study has explored regulation of Gm in AP-firing slow-twitch fibers of soleus muscle and compared it to Gm dynamics in fast-twitch fibers. It further explored aspects of the cellular signaling that conveyed regulation of Gm in AP-firing fibers. Thus, in both fiber types, AP firing first triggered protein kinase C (PKC)-dependent ClC-1 channel inhibition that reduced Gm by ∼50%. Experiments with dantrolene showed that AP-triggered SR Ca2+ release activated this PKC-mediated ClC-1 channel inhibition that was associated with reduced rheobase current and improved function of depolarized muscles, indicating that the reduced Gm enhanced muscle fiber excitability. In fast-twitch fibers, the late rise in Gm was accelerated by glucose-free conditions, whereas it was postponed when intermittent resting periods were introduced during AP firing. Remarkably, elevation of Gm was never encountered in AP-firing slow-twitch fibers, even after 15,000 APs. These observations implicate metabolic depression in the elevation of Gm in AP-firing fast-twitch fibers. It is concluded that regulation of Gm is a general phenomenon in AP-firing muscle, and that differences in Gm regulation may contribute to the different phenotypes of fast- and slow-twitch muscle.

scholarly journals lncRNA-Six1 Is a Target of miR-1611 that Functions as a ceRNA to Regulate Six1 Protein Expression and Fiber Type Switching in Chicken Myogenesis

Cells ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 243 ◽  
Author(s):  
Manting Ma ◽  
Bolin Cai ◽  
Liang Jiang ◽  
Bahareldin Ali Abdalla ◽  
Zhenhui Li ◽  
...  
Keyword(s):  
Fiber Type ◽  
Muscle Fibers ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Proliferation And Differentiation ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Emerging studies indicate important roles for non-coding RNAs (ncRNAs) as essential regulators in myogenesis, but relatively less is known about their function. In our previous study, we found that lncRNA-Six1 can regulate Six1 in cis to participate in myogenesis. Here, we studied a microRNA (miRNA) that is specifically expressed in chickens (miR-1611). Interestingly, miR-1611 was found to contain potential binding sites for both lncRNA-Six1 and Six1, and it can interact with lncRNA-Six1 to regulate Six1 expression. Overexpression of miR-1611 represses the proliferation and differentiation of myoblasts. Moreover, miR-1611 is highly expressed in slow-twitch fibers, and it drives the transformation of fast-twitch muscle fibers to slow-twitch muscle fibers. Together, these data demonstrate that miR-1611 can mediate the regulation of Six1 by lncRNA-Six1, thereby affecting proliferation and differentiation of myoblasts and transformation of muscle fiber types.

scholarly journals Comparison of regulated passive membrane conductance in action potential–firing fast- and slow-twitch muscle

2010 ◽  
Vol 135 (2) ◽  
pp. 171-171
Author(s):  
Thomas Holm Pedersen ◽  
William Alexander Macdonald ◽  
Frank Vincenzo de Paoli ◽  
Iman Singh Gurung ◽  
Ole Bækgaard Nielsen
Keyword(s):  
Action Potential ◽  
Membrane Conductance ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Slow Twitch Muscle ◽  
Slow Twitch ◽  
Passive Membrane

scholarly journals Comparison of regulated passive membrane conductance in action potential–firing fast- and slow-twitch muscle

2009 ◽  
Vol 134 (6) ◽  
pp. 525-525 ◽  
Author(s):  
Thomas Holm Pedersen ◽  
William Alexander Macdonald ◽  
Frank Vincenzo de Paoli ◽  
Iman Singh Gurung ◽  
Ole Bækgaard Nielsen
Keyword(s):  
Action Potential ◽  
Membrane Conductance ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Slow Twitch Muscle ◽  
Slow Twitch ◽  
Passive Membrane

Na current density at and away from end plates on rat fast- and slow-twitch skeletal muscle fibers

1992 ◽  
Vol 262 (1) ◽  
pp. C229-C234 ◽  
Author(s):  
R. L. Ruff
Keyword(s):  
Skeletal Muscle ◽  
Current Density ◽  
Muscle Fibers ◽  
Postsynaptic Membrane ◽  
Na Current ◽  
End Plate ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Na current density and membrane capacitance were studied with the loose patch voltage clamp technique on rat fast- and slow-twitch skeletal muscle fibers at three different regions on the fibers: 1) the end plate border, 2) greater than 200 microns from the end plate (extrajunctional), and 3) on the end plate postsynaptic membrane. Fibers were treated with collagenase to improve visualization of the end plate and to enzymatically remove the nerve terminal. The capacitance of membrane patches was similar on fast- and slow-twitch fibers and patches of membrane on the end plate had twice the capacitance of patches elsewhere. For fast- and slow-twitch fibers, the sizes of the Na current normalized to the area of the patch were as follows: end plate greater than end plate border greater than extrajunctional. For both types of fibers, the amplitudes of the Na current normalized to the capacitance of the membrane patch were as follows: end plate approximately end plate border greater than extrajunctional. At each of the three regions, the Na current densities were larger on fast-twitch fibers and fast-twitch fibers had a larger increase in Na current density at the end plate border compared with extrajunctional membrane.

scholarly journals Calcium accumulation by the sarcoplasmic reticulum in two populations of chemically skinned human muscle fibers. Effects of calcium and cyclic AMP.

1982 ◽  
Vol 79 (4) ◽  
pp. 603-632 ◽  
Author(s):  
G Salviati ◽  
M M Sorenson ◽  
A B Eastwood
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cyclic Amp ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Wide Range ◽  
Ca Uptake ◽  
Human Muscles ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

In previous efforts to characterize sarcoplasmic reticulum function in human muscles, it has not been possible to distinguish the relative contributions of fast-twitch and slow-twitch fibers. In this study, we have used light scattering and 45Ca to monitor Ca accumulation by the sarcoplasmic reticulum of isolated, chemically skinned human muscle fibers in the presence and absence of oxalate. Oxalate (5 mM) increased the capacity for Ca accumulation by a factor of 35 and made it possible to assess both rate of Ca uptake and relative sarcoplasmic reticulum volume in individual fibers. At a fixed ionized Ca concentration, the rate and maximal capacity (an index of sarcoplasmic reticulum volume) both varied over a wide range, but fibers fell into two distinct groups (fast and slow). Between the two groups, there was a 2- to 2.5-fold difference in oxalate-supported Ca uptake rates, but no difference in average sarcoplasmic reticulum volumes. Intrinsic differences in sarcoplasmic reticulum function (Vmax, K0.5, and n) were sought to account for the distinction between fast and slow groups. In both groups, rate of Ca accumulation increased sigmoidally as [Ca++] was increased from 0.1 to 1 microM. Apparent affinities for Ca++ (K0.5) were similar in the two groups, but slow fibers had a lower Vmax and larger n values. Slow fibers also differed from fast fibers in responding with enhanced Ca uptake upon addition of cyclic AMP (10(-6) M, alone or with protein kinase). Acceleration by cyclic AMP was adequate to account for adrenaline-induced increases in relaxation rates previously observed in human muscles containing mixtures in fast-twitch and slow-twitch fibers.

S-nitrosylation and S-glutathionylation of Cys134 on troponin I have opposing competitive actions on Ca2+ sensitivity in rat fast-twitch muscle fibers

2017 ◽  
Vol 312 (3) ◽  
pp. C316-C327 ◽  
Author(s):  
T. L. Dutka ◽  
J. P. Mollica ◽  
C. R. Lamboley ◽  
V. C. Weerakkody ◽  
D. W. Greening ◽  
...  
Keyword(s):  
Troponin I ◽  
Muscle Fibers ◽  
Contractile Apparatus ◽  
Slow Twitch ◽  
Mechanistic Basis ◽  
Opposing Effects ◽  
Slow Twitch Fibers ◽  
Competitive Actions ◽  
Fast Twitch ◽  
Biotin Switch

Nitric oxide is generated in skeletal muscle with activity and decreases Ca2+ sensitivity of the contractile apparatus, putatively by S-nitrosylation of an unidentified protein. We investigated the mechanistic basis of this effect and its relationship to the oxidation-induced increase in Ca2+ sensitivity in mammalian fast-twitch (FT) fibers mediated by S-glutathionylation of Cys134 on fast troponin I (TnIf). Force-[Ca2+] characteristics of the contractile apparatus in mechanically skinned fibers were assessed by direct activation with heavily Ca2+-buffered solutions. Treatment with S-nitrosylating agents, S-nitrosoglutathione (GSNO) or S-nitroso- N-acetyl-penicillamine (SNAP), decreased pCa50 ( = −log10 [Ca2+] at half-maximal activation) by ~−0.07 pCa units in rat and human FT fibers without affecting maximum force, but had no effect on rat and human slow-twitch fibers or toad or chicken FT fibers, which all lack Cys134. The Ca2+ sensitivity decrease was 1) fully reversed with dithiothreitol or reduced glutathione, 2) at least partially reversed with ascorbate, indicative of involvement of S-nitrosylation, and 3) irreversibly blocked by low concentration of the alkylating agent, N-ethylmaleimide (NEM). The biotin-switch assay showed that both GSNO and SNAP treatments caused S-nitrosylation of TnIf. S-glutathionylation pretreatment blocked the effects of S-nitrosylation on Ca2+ sensitivity, and vice-versa. S-nitrosylation pretreatment prevented NEM from irreversibly blocking S-glutathionylation of TnIf and its effects on Ca2+ sensitivity, and likewise S-glutathionylation pretreatment prevented NEM block of S-nitrosylation. Following substitution of TnIf into rat slow-twitch fibers, S-nitrosylation treatment caused decreased Ca2+ sensitivity. These findings demonstrate that S-nitrosylation and S-glutathionylation exert opposing effects on Ca2+ sensitivity in mammalian FT muscle fibers, mediated by competitive actions on Cys134 of TnIf.

scholarly journals Intracellular calcium movements during excitation–contraction coupling in mammalian slow-twitch and fast-twitch muscle fibers

2012 ◽  
Vol 139 (4) ◽  
pp. 261-272 ◽  
Author(s):  
Stephen M. Baylor ◽  
Stephen Hollingworth
Keyword(s):  
Action Potentials ◽  
Muscle Fibers ◽  
Mouse Muscle ◽  
Contraction Coupling ◽  
Individual Mouse ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch ◽  
Indicator Dye

In skeletal muscle fibers, action potentials elicit contractions by releasing calcium ions (Ca2+) from the sarcoplasmic reticulum. Experiments on individual mouse muscle fibers micro-injected with a rapidly responding fluorescent Ca2+ indicator dye reveal that the amount of Ca2+ released is three- to fourfold larger in fast-twitch fibers than in slow-twitch fibers, and the proportion of the released Ca2+ that binds to troponin to activate contraction is substantially smaller.

scholarly journals Carbonic anhydrase activity in skeletal muscle fiber types, axons, spindles, and capillaries of rat soleus and extensor digitorum longus muscles.

1982 ◽  
Vol 30 (12) ◽  
pp. 1275-1288 ◽  
Author(s):  
D A Riley ◽  
S Ellis ◽  
J Bain
Keyword(s):  
Carbonic Anhydrase ◽  
Extensor Digitorum Longus ◽  
Muscle Fibers ◽  
Extensor Digitorum ◽  
Female Rats ◽  
Male Rats ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Slow Twitch ◽  
Fast Twitch

Carbonic anhydrase (CA) activities were studied in soluble extracts and cryostat sections of skeletal muscles from prepubertal and postpubertal rats. Acetazolamide inhibition was utilized to distinguish between activities of the acetazolamide-sensitive (CA I and II) and acetazolamide-resistant (CA III) forms of the enzyme. The inhibition studies indicated that fast-twitch oxidative-glycolytic muscle fibers contained both the sensitive and resistant forms of CA. Acetazolamide-sensitive activity was localized within muscle fibers, axons, myelin, and capillaries. Axoplasmic staining was restricted to subpopulations of myelinated axons in both the dorsal and ventral roots. Soleus muscles exhibited significantly greater activity of CA III than extensor digitorum longus muscles at all ages examined. CA III was richest in slow-twitch oxidative and intrafusal fibers. During puberty, soleus muscle fibers matured and converted from fast-twitch oxidative-glycolytic to slow-twitch oxidative fibers. There was a shift from the sensitive to the resistant form of CA; CA III activity increased about sevenfold. This activity peaked earlier in the muscles of female rats than male rats. These results demonstrated a complex distribution of CA isozymes in the neuromuscular system and pointed out that isozyme content depends on both the type of muscle and the age and sex of the animal.

Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta 2-receptor agonist

1988 ◽  
Vol 254 (6) ◽  
pp. E726-E732 ◽  
Author(s):  
R. J. Zeman ◽  
R. Ludemann ◽  
T. G. Easton ◽  
J. D. Etlinger
Keyword(s):  
Muscle Fiber ◽  
Receptor Agonist ◽  
Fiber Type ◽  
Fiber Types ◽  
Cross Sectional ◽  
Type Composition ◽  
Slow Twitch ◽  
Beta 2 ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Chronic treatment of rats with clenbuterol, a beta 2-receptor agonist (8–12 wk), caused hypertrophy of histochemically identified fast- but not slow-twitch fibers within the soleus, while the mean areas of both fiber types were increased in the extensor digitorum longus (EDL). In contrast, treatment with the beta 2-receptor antagonist, butoxamine, reduced fast-twitch fiber size in both muscles. In the solei and to a lesser extent in the EDLs, the ratio of the number of fast- to slow-twitch fibers was increased by clenbuterol, while the opposite was observed with butoxamine. The muscle fiber hypertrophy observed in the EDL was accompanied by parallel increases in maximal tetanic tension and muscle cross-sectional area, while in the solei, progressive increases in rates of force development and relaxation toward values typical of fast-twitch muscles were also observed. Our results suggest a role of beta 2-receptors in regulating muscle fiber type composition as well as growth.

scholarly journals Myofibrillar regulatory mechanisms of stretch activation in mammalian striated muscle

2017 ◽  
Author(s):  
◽  
Joel C. Robinett
Keyword(s):  
Skeletal Muscle ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Stretch Activation ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Low Levels ◽  
Slow Twitch Fibers ◽  
Fast Twitch ◽  
Transient Force

Stretch activation is described as a delayed increase in force after an imposed stretch. This process is essential in the flight muscles of many insects and is also observed, to some degree, in mammalian striated muscles. The mechanistic basis for stretch activation remains uncertain, although it appears to involve cooperative activation of the thin filaments (12, 80). The purpose of this study was to address myofibrillar regulatory mechanisms of stretch activation in mammalian striated muscle. For these studies, permeabilized rat slow-twitch and fast-twitch skeletal muscle fibers were mounted between a force transducer and motor, and a slack-re-stretch maneuver was performed over a range of Ca[superscript 2+] activation levels. Following slack-re-stretch there was a stretch activation process that often resulted in a transient force overshoot (P[subscript TO]), which was quantified relative to steady-state isometric force. P[subscript TO] was highly dependent upon Ca[superscript 2+] activation level, and the relative magnitude of P[subscript TO] was greater in slow-twitch fibers than fast-twitch fibers. In both slow-twitch and fast-twitch fibers, force redevelopment involved a fast, Ca[superscript 2+] activation dependent process (k1) and a slower, less activation dependent process (k2). Interestingly, the two processes converged at low levels of Ca[superscript 2+] activation in both fiber types. P[subscript TO] also contained a relaxation phase, which progressively slowed as Ca[superscript 2+] activation levels increased and was more Ca[superscript 2+] activation dependent in slow-twitch fibers. These results suggest that stretch activation may not be solely regulated by the extent of apparent cooperative activation of force due to a higher relative level of stretch activation in the less cooperative slow-twitch skeletal muscle fiber. Next, we investigated an additional potential molecular mechanism by regulating stretch activation in mammalian striated muscle. Along these lines, our lab has previously observed that PKA-induced phosphorylation of cMyBP-C and cTnI elicited a significant increase in transient force overshoot following slack-re-stretch maneuver in permeabilized cardiac myocytes (29). Interestingly, in slow-twitch skeletal muscle fibers MyBP-C but not ssTnI is phosphorylated by PKA (28). We, thus, took advantage of this variation in substrates phosphorylated by PKA to investigate the effects of PKA-induced phosphorylation of MyBP-C on stretch activation in slow-twitch skeletal muscle fibers. Following PKA treatment of skinned slow-twitch skeletal muscle fibers, the magnitude of P[subscript TO] more than doubled, but this only occurred at low levels of Ca[superscript 2+] activation (i.e., [approximately]25% maximal Ca[superscript 2+] activated force). Also, force redevelopment rates were significantly increased over the entire range of Ca[superscript 2+] activation levels following PKA treatment. In a similar manner, force decay rates showed a tendency of being faster following PKA treatment, however, were only statistically significantly faster at 50% Ca[superscript 2+] activation. Overall, these results are consistent with a model whereby stretch transiently increases the number of cross-bridges made available for force generation and PKA phosphorylation of MyBP-C enhances these stretch activation processes.

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