Effect of electrical stimulation on intracellular triacylglycerol in isolated skeletal muscle

1990 ◽  
Vol 68 (1) ◽  
pp. 348-354 ◽  
Author(s):  
J. F. Hopp ◽  
W. K. Palmer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Glucose Control ◽  
Muscle Preparation ◽  
Bicarbonate Buffer ◽  
Intermittent Stimulation ◽  
Flexor Digitorum Brevis ◽  
Muscle Groups ◽  
Flexor Digitorum

The contribution of intracellular triacylglycerol (TG) as a substrate for skeletal muscle during electrical stimulation is equivocal. Therefore, the purpose of this study was to investigate the effect of electrical stimulation on the TG content in the isolated intact rat flexor digitorum brevis skeletal muscle preparation by use of two different stimulation protocols. Muscles were electrically stimulated for 1 h either continuously at 1 Hz or intermittently (30 s on, 60 s off) at 5 Hz while incubated in 21 degrees C Krebs bicarbonate buffer (pH 7.4) that contained 11 mM glucose. Control muscles were either frozen immediately after excision or incubated for 1 h. TG content was significantly decreased (P less than 0.05) compared with control concentrations in both stimulated muscle groups, with the greatest reduction (60%) occurring after 5-Hz intermittent stimulation. These data indicate that intramuscular TG is hydrolyzed in response to electrical stimulation in the isolated flexor digitorum brevis muscle preparation. In addition, the type of stimulation (higher frequency intermittent vs. lower frequency continuous) employed influences the amount of intracellular TG hydrolyzed.

Electrical stimulation alters fatty acid metabolism in isolated skeletal muscle

1990 ◽  
Vol 68 (6) ◽  
pp. 2473-2481 ◽  
Author(s):  
J. F. Hopp ◽  
W. K. Palmer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Fatty Acid ◽  
Energy Production ◽  
Plasma Free Fatty Acid ◽  
Intermittent Stimulation ◽  
Flexor Digitorum Brevis ◽  
Plasma Ffa ◽  
Flexor Digitorum

Little is known about the contribution of plasma free fatty acid (FFA) and intramuscular triacylglycerol (TG) as substrates for energy production during prolonged electrical stimulation of skeletal muscle. The purpose of this study was to investigate the effects of continuous and intermittent electrical stimulation protocols of different intensities on exogenous FFA oxidation, exogenous FFA incorporation into intracellular TG, and intracellular TG content in the isolated in vitro rat flexor digitorum brevis muscle preparation. Muscles were electrically stimulated for 0.5 h continuously at 0.2 Hz or intermittently (30 s on, 60 s off) at 0.2, 0.4, 0.8, and 5.0 Hz while incubated at 37 degrees C in 0.5 mM palmitate-3% bovine serum albumin medium (pH 7.4) in the presence of insulin (100 microU/ml) and glucose (11 mM). Control muscles were frozen immediately after excision or incubated for 0.5 h. At similar frequencies, less exogenous FFA esterification and more exogenous FFA oxidation occurred during continuous than during intermittent stimulation. As the frequency of intermittent stimulation increased, the amount of exogenous FFA esterified decreased and the amount of exogenous FFA oxidized increased. The data also indicate that at least a portion of TG was constantly being hydrolyzed during electrical stimulation. Under stimulation conditions in which exogenous FFA esterification was below the control (resting muscle) level, intramuscular TG content was significantly decreased compared with control TG content values. Thus both plasma FFA and intramuscular TG are substrates for energy production during electrical stimulation. However, the stimulation parameters employed affect the quantities utilized.

scholarly journals Consequences of SUR2[A478V] Mutation in Skeletal Muscle of Murine Model of Cantu Syndrome

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1791
Author(s):  
Rosa Scala ◽  
Fatima Maqoud ◽  
Nicola Zizzo ◽  
Giuseppe Passantino ◽  
Antonietta Mele ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Katp Channel ◽  
Ex Vivo ◽  
Channel Modulation ◽  
Flexor Digitorum Brevis ◽  
Inflammatory Edema ◽  
Flexor Digitorum ◽  
Channel Currents

(1) Background: Cantu syndrome (CS) arises from gain-of-function (GOF) mutations in the ABCC9 and KCNJ8 genes, which encode ATP-sensitive K+ (KATP) channel subunits SUR2 and Kir6.1, respectively. Most CS patients have mutations in SUR2, the major component of skeletal muscle KATP, but the consequences of SUR2 GOF in skeletal muscle are unknown. (2) Methods: We performed in vivo and ex vivo characterization of skeletal muscle in heterozygous SUR2[A478V] (SUR2wt/AV) and homozygous SUR2[A478V] (SUR2AV/AV) CS mice. (3) Results: In SUR2wt/AV and SUR2AV/AV mice, forelimb strength and diaphragm amplitude movement were reduced; muscle echodensity was enhanced. KATP channel currents recorded in Flexor digitorum brevis fibers showed reduced MgATP-sensitivity in SUR2wt/AV, dramatically so in SUR2AV/AV mice; IC50 for MgATP inhibition of KATP currents were 1.9 ± 0.5 × 10−5 M in SUR2wt/AV and 8.6 ± 0.4 × 10−6 M in WT mice and was not measurable in SUR2AV/AV. A slight rightward shift of sensitivity to inhibition by glibenclamide was detected in SUR2AV/AV mice. Histopathological and qPCR analysis revealed atrophy of soleus and tibialis anterior muscles and up-regulation of atrogin-1 and MuRF1 mRNA in CS mice. (4) Conclusions: SUR2[A478V] “knock-in” mutation in mice impairs KATP channel modulation by MgATP, markedly so in SUR2AV/AV, with atrophy and non-inflammatory edema in different skeletal muscle phenotypes.

scholarly journals Differential impact of mitochondrial positioning on mitochondrial Ca2+ uptake and Ca2+ spark suppression in skeletal muscle

2011 ◽  
Vol 301 (5) ◽  
pp. C1128-C1139 ◽  
Author(s):  
Ann E. Rossi ◽  
Simona Boncompagni ◽  
Lan Wei ◽  
Feliciano Protasi ◽  
Robert T. Dirksen
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Osmotic Shock ◽  
Progressive Increase ◽  
Tetanic Stimulation ◽  
Differential Impact ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Activity Dependent ◽  
Old Mice

Muscle contraction requires ATP and Ca2+ and, thus, is under direct control of mitochondria and the sarcoplasmic reticulum. During postnatal skeletal muscle maturation, the mitochondrial network exhibits a shift from a longitudinal (“longitudinal mitochondria”) to a mostly transversal orientation as a result of a progressive increase in mitochondrial association with Ca2+ release units (CRUs) or triads (“triadic mitochondria”). To determine the physiological implications of this shift in mitochondrial disposition, we used confocal microscopy to monitor activity-dependent changes in myoplasmic (fluo 4) and mitochondrial (rhod 2) Ca2+ in single flexor digitorum brevis (FDB) fibers from 1- to 4-mo-old mice. A robust and sustained Ca2+ accumulation in triadic mitochondria was triggered by repetitive tetanic stimulation (500 ms, 100 Hz, every 2.5 s) in FDB fibers from 4-mo-old mice. Specifically, mitochondrial rhod 2 fluorescence increased 272 ± 39% after a single tetanus and 412 ± 45% after five tetani and decayed slowly over 10 min following the final tetanus. Similar results were observed in fibers expressing mitochondrial pericam, a mitochondrial-targeted ratiometric Ca2+ indicator. Interestingly, sustained mitochondrial Ca2+ uptake following repetitive tetanic stimulation was similar for triadic and longitudinal mitochondria in FDB fibers from 1-mo-old mice, and both mitochondrial populations were found by electron microscopy to be continuous and structurally tethered to the sarcoplasmic reticulum. Conversely, the frequency of osmotic shock-induced Ca2+ sparks per CRU density decreased threefold (from 3.6 ± 0.2 to 1.2 ± 0.1 events·CRU−1·min−1·100 μm−2) during postnatal development in direct linear correspondence ( r2 = 0.95) to an increase in mitochondrion-CRU pairing. Together, these results indicate that mitochondrion-CRU association promotes Ca2+ spark suppression but does not significantly impact mitochondrial Ca2+ uptake.

scholarly journals Effects of myofiber isolation technique on sarcolemma biomechanics

BioTechniques ◽  
2020 ◽  
Vol 69 (5) ◽  
pp. 388-391
Author(s):  
Karla P Garcia-Pelagio ◽  
Stephen JP Pratt ◽  
Richard M Lovering
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Sarcomere Length ◽  
Biomechanical Properties ◽  
Isolation Technique ◽  
Enzymatic Dissociation ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Biomechanical Measurements

Isolated myofibers are commonly used to understand the function of skeletal muscle in vivo. This can involve single isolated myofibers obtained from dissection or from enzymatic dissociation. Isolation via dissection allows control of sarcomere length and preserves tendon attachment but is labor-intensive, time-consuming and yields few viable myofibers. In contrast, enzymatic dissociation is fast and facile, produces hundreds of myofibers, and more importantly reduces the number of muscles/animals needed for studies. Biomechanical properties of the sarcolemma have been studied using myofibers from the extensor digitorum longus, but this has been limited to dissected myofibers, making data collection slow and difficult. We have modified this tool to perform biomechanical measurements of the sarcolemma in dissociated myofibers from the flexor digitorum brevis.

scholarly journals Sarcolipin overexpression improves muscle energetics and reduces fatigue

2015 ◽  
Vol 118 (8) ◽  
pp. 1050-1058 ◽  
Author(s):  
Danesh H. Sopariwala ◽  
Meghna Pant ◽  
Sana A. Shaikh ◽  
Sanjeewa A. Goonasekera ◽  
Jeffery D. Molkentin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Performance ◽  
Force Frequency ◽  
Frequency Curve ◽  
Muscle Energetics ◽  
Store Operated Calcium Entry ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Muscle Contractile ◽  
Frequency Curves

Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression ( Sln OE) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that Sln OE mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that Sln OE EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and Sln OE EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in Sln OE EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from Sln OE mice fatigued significantly less than WT muscles. Interestingly, Sln OE muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in Sln OE EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of Sln OE compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics.

scholarly journals Characterization and utilization of the flexor digitorum brevis for assessing skeletal muscle function

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Michael D. Tarpey ◽  
Adam J. Amorese ◽  
Nicholas P. Balestrieri ◽  
Terence E. Ryan ◽  
Cameron A. Schmidt ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Function ◽  
Skeletal Muscle Function ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

Ouabain stimulates unidirectional and net potassium efflux in resting mammalian skeletal muscle

2001 ◽  
Vol 79 (11) ◽  
pp. 932-941 ◽  
Author(s):  
Thomas J Hawke ◽  
Sarah Lessard ◽  
Lisa Vickery ◽  
Shonda L Lipskie ◽  
Michael I Lindinger
Keyword(s):  
Skeletal Muscle ◽  
Mammalian Skeletal Muscle ◽  
Potassium Efflux ◽  
Hindlimb Muscle ◽  
Flexor Digitorum Brevis ◽  
Baseline Values ◽  
Flexor Digitorum ◽  
Subsequent Addition

The present study compared ouabain-sensitive unidirectional K+ flux into (JinK) and out of (JoutK) perfused rat hindlimb skeletal muscle in situ and mouse flexor digitorum brevis (FDB) in vitro. In situ, 5 mM ouabain inhibited 54 ± 4% of the total JinK in 28 ± 1 min, and increased the net and unidirectional efflux of K+ within 4 min. In contrast, 1.8 mM ouabain inhibited 40 ± 8% of the total JinK in 38 ± 2 min, but did not significantly affect JoutK. In vitro, 1.8 and 0.2 mM ouabain decreased JinK to a greater extent (83 ± 5%) than in situ, but did not significantly affect 42K loss rate compared with controls. The increase in unidirectional K+ efflux (JoutK) with 5 mM ouabain in situ was attributed to increased K+ efflux through cation channels, since addition of barium (1 mM) to ouabain-perfused muscles returned JoutK to baseline values within 12 min. Perfusion with 5 mM ouabain plus 2 mM tetracaine for 30 min decreased JinK 46 ± 9% (0.30 ± 0.03 to 0.16 ± 0.02 µmol·min–1·g–1), however tetracaine was unable to abolish the ouabain-induced increase in unidirectional K+ efflux. In both rat hindlimb and mouse FDB, tetracaine had no effect on JoutK. Perfusion of hindlimb muscle with 0.1 mM tetrodotoxin (TTX, a Na+ channel blocker) decreased JinK by 15 ± 1%, but had no effect on JoutK; subsequent addition of ouabain (5 mM) decreased JinK a further 32 ± 2%. The ouabain-induced increase in unidirectional K+ efflux did not occur when TTX was perfused prior to and during perfusion with 5 mM ouabain. We conclude that 5 mM ouabain increases the unidirectional efflux of K+ from skeletal muscle through a barium and TTX-sensitive pathway, suggestive of voltage sensitive Na+ channels, in addition to inhibiting Na+/K+-ATPase activity.Key words: cardiac glycoside, Na,K pump, K+ channels, Na+ channels, perfused rat hindlimb, flexor digitorum brevis, TTX, barium, tetracaine.

Disruption of microtubules in rat skeletal muscle does not inhibit insulin- or contraction-stimulated glucose transport

2003 ◽  
Vol 285 (4) ◽  
pp. E836-E844 ◽  
Author(s):  
Hua Ai ◽  
Evelyn Ralston ◽  
Hans P. M. M. Lauritzen ◽  
Henrik Galbo ◽  
Thorkil Ploug
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Immunofluorescence Microscopy ◽  
Fiber Type ◽  
Force Production ◽  
Rat Skeletal Muscle ◽  
Microtubule Network ◽  
Type Composition ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

Insulin and muscle contractions stimulate glucose transport in skeletal muscle through a translocation of intracellular GLUT4 glucose transporters to the cell surface. Judged by immunofluorescence microscopy, part of the GLUT4 storage sites is associated with the extensive microtubule cytoskeleton found in all muscle fibers. Here, we test whether microtubules are required mediators of the effect of insulin and contractions. In three different incubated rat muscles with distinct fiber type composition, depolymerization of microtubules with colchicine for ≤8 h did not inhibit insulin- or contraction-stimulated 2-deoxyglucose transport or force production. On the contrary, colchicine at least partially prevented the ∼30% decrease in insulin-stimulated transport that specifically developed during 8 h of incubation in soleus muscle but not in flexor digitorum brevis or epitrochlearis muscles. In contrast, nocodazole, another microtubule-disrupting drug, rapidly and dose dependently blocked insulin- and contraction-stimulated glucose transport. A similar discrepancy between colchicine and nocodazole was also found in their ability to block glucose transport in muscle giant “ghost” vesicles. This suggests that the ability of insulin and contractions to stimulate glucose transport in muscle does not require an intact microtubule network and that nocodazole inhibits glucose transport independently of its microtubule-disrupting effect.

scholarly journals Length-dependent Ca2+ activation in skeletal muscle fibers from mammalians

2016 ◽  
Vol 311 (2) ◽  
pp. C201-C211 ◽  
Author(s):  
Dilson E. Rassier ◽  
Fábio C. Minozzo
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Action Potential ◽  
Skeletal Muscles ◽  
External Concentration ◽  
The Core ◽  
Experimental Media ◽  
Intracellular Ca ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum

We tested the hypotheses that 1) a decrease in activation of skeletal muscles at short sarcomere lengths (SLs) is caused by an inhibition of Ca2+ release from the sarcoplasmic reticulum (SR), and 2) the decrease in Ca2+ would be caused by an inhibition of action potential conduction from the periphery to the core of the fibers. Intact, single fibers dissected from the flexor digitorum brevis from mice were activated at different SLs, and intracellular Ca2+ was imaged with confocal microscopy. Force decreased at SLs shorter than 2.1 μm, while Ca2+ concentration decreased at SLs below 1.9 μm. The concentration of Ca2+ at short SL was lower at the core than at the peripheries of the fiber. When the external concentration of Na+ was decreased in the experimental media, impairing action potential conduction, Ca2+ gradients were observed in all SLs. When caffeine was used in the experimental media, the gradients of Ca2+ were abolished. We concluded that there is an inhibition of Ca2+ release from the sarcoplasmic reticulum (SR) at short SLs, which results from a decreased conduction of action potential from the periphery to the core of the fibers.

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