scholarly journals Comparison of the effects of inorganic phosphate on caffeine-induced Ca2+ release in fast- and slow-twitch mammalian skeletal muscle

2008 ◽  
Vol 294 (1) ◽  
pp. C97-C105 ◽  
Author(s):  
Giuseppe S. Posterino ◽  
Stacey L. Dunn
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Inorganic Phosphate ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Creatine Phosphate ◽  
Mammalian Skeletal Muscle ◽  
Time Integral ◽  
Slow Twitch ◽  
Fast Twitch

We compared the effects of 50 mM Pi on caffeine-induced Ca2+ release in mechanically skinned fast-twitch (FT) and slow-twitch (ST) skeletal muscle fibers of the rat. The time integral (area) of the caffeine response was reduced by ∼57% (FT) and ∼27% (ST) after 30 s of exposure to 50 mM Pi in either the presence or absence of creatine phosphate (to buffer ADP). Differences in the sarcoplasmic reticulum (SR) Ca2+ content between FT and ST fibers [∼40% vs. 100% SR Ca2+ content (pCa 6.7), respectively] did not contribute to the different effects of Pi observed; underloading the SR of ST fibers so that the SR Ca2+ content approximated that of FT fibers resulted in an even smaller (∼21%), but not significant, reduction in caffeine-induced Ca2+ release by Pi. These observed differences between FT and ST fibers could arise from fiber-type differences in the ability of the SR to accumulate Ca2+-Pi precipitate. To test this, fibers were Ca2+ loaded in the presence of 50 mM Pi. In FT fibers, the maximum SR Ca2+ content (pCa 6.7) was subsequently increased by up to 13 times of that achieved when loading for 2 min in the absence of Pi. In ST fibers, the SR Ca2+ content was only doubled. These data show that Ca2+ release in ST fibers was less affected by Pi than FT fibers, and this may be due to a reduced capacity of ST SR to accumulate Ca2+-Pi precipitate. This may account, in part, for the fatigue-resistant nature of ST fibers.

scholarly journals Activity-dependent nuclear translocation and intranuclear distribution of NFATc in adult skeletal muscle fibers

2001 ◽  
Vol 155 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Yewei Liu ◽  
Zoltán Cseresnyés ◽  
William R. Randall ◽  
Martin F. Schneider
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Nuclear Translocation ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Adult Skeletal Muscle ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
Nuclear Foci ◽  
Fast Twitch

TTranscription factor nuclear factor of activated T cells NFATc (NFATc1, NFAT2) may contribute to slow-twitch skeletal muscle fiber type–specific gene expression. Green fluorescence protein (GFP) or FLAG fusion proteins of either wild-type or constitutively active mutant NFATc [NFATc(S→A)] were expressed in cultured adult mouse skeletal muscle fibers from flexor digitorum brevis (predominantly fast-twitch). Unstimulated fibers expressing NFATc(S→A) exhibited a distinct intranuclear pattern of NFATc foci. In unstimulated fibers expressing NFATc–GFP, fluorescence was localized at the sarcomeric z-lines and absent from nuclei. Electrical stimulation using activity patterns typical of slow-twitch muscle, either continuously at 10 Hz or in 5-s trains at 10 Hz every 50 s, caused cyclosporin A–sensitive appearance of fluorescent foci of NFATc–GFP in all nuclei. Fluorescence of nuclear foci increased during the first hour of stimulation and then remained constant during a second hour of stimulation. Kinase inhibitors and ionomycin caused appearance of nuclear foci of NFATc–GFP without electrical stimulation. Nuclear translocation of NFATc–GFP did not occur with either continuous 1 Hz stimulation or with the fast-twitch fiber activity pattern of 0.1-s trains at 50 Hz every 50 s. The stimulation pattern–dependent nuclear translocation of NFATc demonstrated here could thus contribute to fast-twitch to slow-twitch fiber type transformation.

scholarly journals Localization of sarcoplasmic reticulum proteins in rat skeletal muscle by immunofluorescence.

1979 ◽  
Vol 80 (2) ◽  
pp. 372-384 ◽  
Author(s):  
A O Jorgensen ◽  
V Kalnins ◽  
D H MacLennan
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Immunofluorescent Staining ◽  
Mammalian Skeletal Muscle ◽  
Rat Skeletal Muscle ◽  
Ultrastructural Studies ◽  
Band Region ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Cryostat Sections

Ca++-Mg++-dependent ATPase and calsequestrin, the major intrinsic and extrinsic proteins, respectively, of the sarcoplasmic reticulum, were localized in cryostat sections of adult rat skeletal muscle by immunofluorescent staining and phase-contrast microscopy. Relatively high concentrations of both the ATPase and calsequestrin were found in fast-twitch myofibers while a very low concentration of the ATPase and a moderate concentration of calsequestrin were found in slow-twitch myofibers. These findings are consistent with previous biochemical studies of the isolated sarcoplasmic reticulum of slow-twitch and fast-twitch mammalian muscles. The distribution of the ATPase in muscle fibers is distinctly different from that of calsequestrin. While calsequestrin is present only near the interface between the I- and A-band regions of the sarcomere, the ATPase is found throughout the I-band region as well as in the center of the A-band region. In comparing these results with in situ ultrastructural studies of the distribution of sarcoplasmic reticulum in fast-twitch muscle, it appears that the ATPase is rather uniformly distributed throughout the sarcoplasmic reticulum while calsequestrin is almost exclusively confined to those regions of the membrane system which correspond to terminal cisternae. Fluorescent staining with these antisera was not observed in vascular smooth muscle cells present in the cryostat sections of the mammalian skeletal muscle used in this study.

scholarly journals A myosin-based mechanism for stretch activation and its possible role revealed by varying phosphate concentration in fast and slow mouse skeletal muscle fibers

2019 ◽  
Vol 317 (6) ◽  
pp. C1143-C1152 ◽  
Author(s):  
Chad R. Straight ◽  
Kaylyn M. Bell ◽  
Jared N. Slosberg ◽  
Mark S. Miller ◽  
Douglas M. Swank
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Muscle Length ◽  
Power Stroke ◽  
Mammalian Skeletal Muscle ◽  
Stretch Activation ◽  
Force Ratio ◽  
Slow Twitch ◽  
Fast Twitch

Stretch activation (SA) is a delayed increase in force following a rapid muscle length increase. SA is best known for its role in asynchronous insect flight muscle, where it has replaced calcium’s typical role of modulating muscle force levels during a contraction cycle. SA also occurs in mammalian skeletal muscle but has previously been thought to be too low in magnitude, relative to calcium-activated (CA) force, to be a significant contributor to force generation during locomotion. To test this supposition, we compared SA and CA force at different Pi concentrations (0–16 mM) in skinned mouse soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscle fibers. CA isometric force decreased similarly in both muscles with increasing Pi, as expected. SA force decreased with Pi in EDL (40%), leaving the SA to CA force ratio relatively constant across Pi concentrations (17–25%). In contrast, SA force increased in soleus (42%), causing a quadrupling of the SA to CA force ratio, from 11% at 0 mM Pi to 43% at 16 mM Pi, showing that SA is a significant force modulator in slow-twitch mammalian fibers. This modulation would be most prominent during prolonged muscle use, which increases Pi concentration and impairs calcium cycling. Based upon our previous Drosophila myosin isoform studies and this work, we propose that in slow-twitch fibers a rapid stretch in the presence of Pi reverses myosin’s power stroke, enabling quick rebinding to actin and enhanced force production, while in fast-twitch fibers, stretch and Pi cause myosin to detach from actin.

Effect of clenbuterol on sarcoplasmic reticulum function in single skinned mammalian skeletal muscle fibers

1998 ◽  
Vol 274 (6) ◽  
pp. C1718-C1726 ◽  
Author(s):  
Anthony J. Bakker ◽  
Stewart I. Head ◽  
Anthony C. Wareham ◽  
D. George Stephenson
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Rattus Norvegicus ◽  
Extensor Digitorum Longus ◽  
Muscle Fibers ◽  
Mammalian Skeletal Muscle ◽  
Direct Effects ◽  
Contraction Coupling ◽  
Slow Twitch

We examined the effect of the β2-agonist clenbuterol (50 μM) on depolarization-induced force responses and sarcoplasmic reticulum (SR) function in muscle fibers of the rat ( Rattus norvegicus; killed by halothane overdose) that had been mechanically skinned, rendering the β2-agonist pathway inoperable. Clenbuterol decreased the peak of depolarization-induced force responses in the extensor digitorum longus (EDL) and soleus fibers to 77.2 ± 9.0 and 55.6 ± 5.4%, respectively, of controls. The soleus fibers did not recover. Clenbuterol significantly and reversibly reduced SR Ca2+loading in EDL and soleus fibers to 81.5 ± 2.8 and 78.7 ± 4.0%, respectively, of controls. Clenbuterol also produced an ∼25% increase in passive leak of Ca2+ from the SR of the EDL and soleus fibers. These results indicate that clenbuterol has direct effects on fast- and slow-twitch skeletal muscle, in the absence of the β2-agonist pathway. The increased Ca2+ leak in the triad region may lead to excitation-contraction coupling damage in the soleus fibers and could also contribute to the anabolic effect of clenbuterol in vivo.

Acidosis has no effect on the ATP cost of contraction in cat fast- and slow-twitch skeletal muscles

1997 ◽  
Vol 272 (2) ◽  
pp. C485-C490 ◽  
Author(s):  
S. J. Harkema ◽  
G. R. Adams ◽  
R. A. Meyer
Keyword(s):  
Skeletal Muscle ◽  
Ex Vivo ◽  
Isometric Force ◽  
Mammalian Skeletal Muscle ◽  
Time Integral ◽  
Nuclear Magnetic Resonance Spectra ◽  
Before And After ◽  
Muscle Types ◽  
Slow Twitch ◽  
Fast Twitch

Studies of skinned fibers suggest that the rate of ATP turnover in skeletal muscle is depressed by acidosis. To examine whether this occurs in intact muscles, the ATP cost of isometric contractions was measured in ex vivo, arterially perfused cat biceps (predominantly fast-twitch) and soleus (slow-twitch) muscles under normocapnic (5% CO2) and hypercapnic (70% CO2) conditions. Hypercapnia decreased extracellular pH from 7.4 to 6.7 and intracellular pH from 7.1 to 6.5 (soleus) or 6.6 (biceps) but had no significant effect on the phosphocreatine (PCr)-to-ATP ratio in muscles at rest. The ATP cost of contraction was estimated from PCr changes, measured by gating the acquisition of 31P-nuclear magnetic resonance spectra to times before and after brief tetani (1 s at 100 Hz and 2 s at 25 Hz for biceps and soleus, respectively) or 10-s trains of twitches (2 and 1 Hz, respectively). Peak isometric force and the ATP cost of tetanic contraction (PCr/force x time integral) were not significantly different under hypercapnic compared with normocapnic conditions in either muscle (mean: 7.97 and 2.44 micromol x kg(-1) x s(-1) for biceps and soleus, respectively). Twitch force and the ATP cost per twitch decreased by nearly 50% during hypercapnic perfusion in both muscle types. The results indicate that hypercapnic acidosis has no significant effect on the ATPase rate per active myosin head in intact mammalian skeletal muscle.

Sequential effects of GSNO and H2O2 on the Ca2+ sensitivity of the contractile apparatus of fast- and slow-twitch skeletal muscle fibers from the rat

2009 ◽  
Vol 296 (5) ◽  
pp. C1015-C1023 ◽  
Author(s):  
Timothy Spencer ◽  
Giuseppe S. Posterino
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Contractile Apparatus ◽  
Sequential Effects ◽  
No Donor ◽  
Skeletal Muscle Fibers ◽  
Slow Twitch ◽  
The Individual ◽  
Fast Twitch

Reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and nitric oxide (NO), have been shown to differentially alter the Ca2+ sensitivity of the contractile apparatus of fast-twitch skeletal muscle, leading to the proposal that normal muscle function is controlled by perturbations in the amounts of these two groups of molecules ( 28 ). However, no previous studies have examined whether these opposing actions are retained when the contractile apparatus is subjected to both molecule types. Using mechanically skinned fast- and slow-twitch skeletal muscle fibers of the rat, we compared the effects of sequential addition of nitrosoglutathione (GSNO), a NO donor, and H2O2 on the Ca2+ sensitivity of the contractile apparatus. As expected from previous reports in fast-twitch fibers, when added separately, GSNO (1 mM) reduced the Ca2+ sensitivity of the contractile apparatus, whereas H2O2 (10 mM; added during contractions) increased the Ca2+ sensitivity of the contractile apparatus. When added sequentially to the same fiber, such that the oxidation by one molecule (e.g., GSNO) preceded the oxidation by the other (e.g., H2O2), and vice versa, the individual effects of both molecules on the Ca2+ sensitivity were retained. Interestingly, neither molecule had any effect on the Ca2+ sensitivity of slow-twitch skeletal muscle. The data show that H2O2 and GSNO retain the capacity to independently affect the contractile apparatus to modulate force. Furthermore, the absence of effects in slow-twitch muscle may further explain why this fiber type is relatively insensitive to fatigue.

Calcium phosphate precipitation in the sarcoplasmic reticulum reduces action potential-mediated Ca2+ release in mammalian skeletal muscle

2005 ◽  
Vol 289 (6) ◽  
pp. C1502-C1512 ◽  
Author(s):  
T. L. Dutka ◽  
L. Cole ◽  
G. D. Lamb
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Muscle Fibers ◽  
Creatine Phosphate ◽  
Release Mechanism ◽  
Mammalian Skeletal Muscle ◽  
Vigorous Exercise ◽  
Tetanic Force ◽  
Fast Twitch Muscle ◽  
Fast Twitch

During vigorous exercise, Pi concentration levels within the cytoplasm of fast-twitch muscle fibers may reach ≥30 mM. Cytoplasmic Pi may enter the sarcoplasmic reticulum (SR) and bind to Ca2+ to form a precipitate (CaPi), thus reducing the amount of releasable Ca2+. Using mechanically skinned rat fast-twitch muscle fibers, which retain the normal action potential-mediated Ca2+ release mechanism, we investigated the consequences of Pi exposure on normal excitation-contraction coupling. The total amount of Ca2+ released from the SR by a combined caffeine/low-Mg2+ concentration stimulus was reduced by ∼20%, and the initial rate of force development slowed after 2-min exposure to 30 mM Pi (with or without the presence creatine phosphate). Peak (50 Hz) tetanic force was also reduced (by ∼25% and ∼45% after 10 and 30 mM Pi exposure, respectively). Tetanic force responses produced after 30 mM Pi exposure were nearly identical to those observed in the same fiber after depletion of total SR Ca2+ by ∼35%. Ca2+ content assays revealed that the total amount of Ca2+ in the SR was not detectably changed by exposure to 30 mM Pi, indicating that Ca2+ had not leaked from the SR but instead formed a precipitate with the Pi, reducing the amount of available Ca2+ for rapid release. These results suggest that CaPi precipitation that occurs within the SR could contribute to the failure of Ca2+ release observed in the later stages of metabolic muscle fatigue. They also demonstrate that the total amount of Ca2+ stored in the SR cannot drop substantially below the normal endogenous level without reducing tetanic force responses.

scholarly journals Six1 and Eya1 Expression Can Reprogram Adult Muscle from the Slow-Twitch Phenotype into the Fast-Twitch Phenotype

2004 ◽  
Vol 24 (14) ◽  
pp. 6253-6267 ◽  
Author(s):  
Raphaelle Grifone ◽  
Christine Laclef ◽  
François Spitz ◽  
Soledad Lopez ◽  
Josiane Demignon ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Slow Twitch Muscle ◽  
Slow Twitch ◽  
Metabolic Properties ◽  
Transcriptional Complex ◽  
High Level ◽  
Fast Twitch ◽  
Aldolase A

ABSTRACT Muscle fibers show great differences in their contractile and metabolic properties. This diversity enables skeletal muscles to fulfill and adapt to different tasks. In this report, we show that the Six/Eya pathway is implicated in the establishment and maintenance of the fast-twitch skeletal muscle phenotype. We demonstrate that the MEF3/Six DNA binding element present in the aldolase A pM promoter mediates the high level of activation of this promoter in fast-twitch glycolytic (but not in slow-twitch) muscle fibers. We also show that among the Six and Eya gene products expressed in mouse skeletal muscle, Six1 and Eya1 proteins accumulate preferentially in the nuclei of fast-twitch muscles. The forced expression of Six1 and Eya1 together in the slow-twitch soleus muscle induced a fiber-type transition characterized by the replacement of myosin heavy chain I and IIA isoforms by the faster IIB and/or IIX isoforms, the activation of fast-twitch fiber-specific genes, and a switch toward glycolytic metabolism. Collectively, these data identify Six1 and Eya1 as the first transcriptional complex that is able to reprogram adult slow-twitch oxidative fibers toward a fast-twitch glycolytic phenotype.

The Adaptive Potential of Skeletal Muscle Fibers

2002 ◽  
Vol 27 (4) ◽  
pp. 423-448 ◽  
Author(s):  
Dirk Pette
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Protein Isoforms ◽  
Mammalian Skeletal Muscle ◽  
Adaptive Potential ◽  
Hybrid Fibers ◽  
Neuromuscular Activity ◽  
Skeletal Muscle Fibers ◽  
Initial Location

Mammalian skeletal muscle fibers display a great adaptive potential. This potential results from the ability of muscle fibers to adjust their molecular, functional, and metabolic properties in response to altered functional demands, such as changes in neuromuscular activity or mechanical loading. Adaptive changes in the expression of myofibrillar and other protein isoforms result in fiber type transitions. These transitions occur in a sequential order and encompass a spectrum of pure and hybrid fibers. Depending on the quality, intensity, and duration of the alterations in functional demand, muscle fibers may undergo functional transitions in the direction of slow or fast, as well as metabolic transitions in the direction of aerobic-oxidative or glycotytic. The maximum range of possible transitions in either direction depends on the fiber phenotype and is determined by its initial location in the fiber spectrum. Key words: Ca-sequestering proteins, energy metabolism, fiber type transition, myofibrillar protein isofonns, myosin, neuromuscular activity

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.

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