Potassium-induced potentiation of subtetanic force in rat skeletal muscles: influences of β2-activation, lactic acid, and temperature

2021 ◽  
Author(s):  
Jonas Hokser Olesen ◽  
Jon Hagen Herskind ◽  
Katja Krustrup Pedersen ◽  
Kristian Overgaard
Keyword(s):  
Lactic Acid ◽  
Skeletal Muscles ◽  
Isometric Force ◽  
Positive Influence ◽  
Increased Temperature ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Isometric Twitch ◽  
Fast Twitch ◽  
Contractile Performance

Purpose: Moderate elevations of [K+]o occur during exercise and have been shown to potentiate force during contractions elicited with subtetanic frequencies. Here, we investigated whether lactic acid (reduced chloride conductance), β2-adrenoceptor activation, and increased temperature would influence the potentiating effect of potassium in slow- and fast-twitch muscle. Methods: Isometric contractions were elicited by electrical stimulation at various frequencies in isolated rat soleus and extensor digitorum longus (EDL) muscles incubated at normal (4 mM) or elevated K+, in combination with either salbutamol (5 μM), lactic acid (18.1 mM), 9-AC (25 μM) or increased temperature (30 to 35°C). Results: Elevating [K+] from 4 mM to 7 mM (soleus) and 10 mM (EDL) potentiated isometric twitch and subtetanic force while slightly reducing tetanic. In EDL, salbutamol further augmented twitch force (+27±3 %, P<0.001) and subtetanic force (+22±4 %, P<0.001). In contrast, salbutamol reduced subtetanic force (-28±6 %, P<0.001) in soleus muscles. Lactic acid and 9-AC had no significant effects on isometric force of muscles already exposed to moderate elevations of [K+]o. The potentiating effect of elevated [K+]o was still well maintained at 35°C. Conclusion: Addition of salbutamol exerts a further force-potentiating effect in fast-twitch but not in slow-twitch muscles already potentiated by moderately elevated [K+]o, whilst neither lactic acid, 9-AC nor increased temperature exerts any further augmentation. However, the potentiating effect of elevated [K+]o was still maintained in the presence of these, thus emphasizing the positive influence of moderately elevated [K+]o for contractile performance during exercise.

scholarly journals Unaffected contractility of diaphragm muscle fibers in humans on mechanical ventilation

2014 ◽  
Vol 307 (6) ◽  
pp. L460-L470 ◽  
Author(s):  
Pleuni E. Hooijman ◽  
Marinus A. Paul ◽  
Ger J. M. Stienen ◽  
Albertus Beishuizen ◽  
Hieronymus W. H. Van Hees ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Muscle Fibers ◽  
Calcium Sensitivity ◽  
Diaphragm Muscle ◽  
Cross Sectional ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Kinetics Of ◽  
Contractile Performance

Several studies have indicated that diaphragm dysfunction develops in patients on mechanical ventilation (MV). Here, we tested the hypothesis that the contractility of sarcomeres, i.e., the smallest contractile unit in muscle, is affected in humans on MV. To this end, we compared diaphragm muscle fibers of nine brain-dead organ donors (cases) that had been on MV for 26 ± 5 h with diaphragm muscle fibers from nine patients (controls) undergoing surgery for lung cancer that had been on MV for less than 2 h. In each diaphragm specimen we determined 1) muscle fiber cross-sectional area in cryosections by immunohistochemical methods and 2) the contractile performance of permeabilized single muscle fibers by means of maximum specific force, kinetics of cross-bridge cycling by rate of tension redevelopment, myosin heavy chain content and concentration, and calcium sensitivity of force of slow-twitch and fast-twitch muscle fibers. In case subjects, we noted no statistically significant decrease in outcomes compared with controls in slow-twitch or fast-twitch muscle fibers. These observations indicate that 26 h of MV of humans is not invariably associated with changes in the contractile performance of sarcomeres in the diaphragm.

Threshold for force potentiation associated with skeletal myosin phosphorylation

1993 ◽  
Vol 265 (6) ◽  
pp. C1456-C1462 ◽  
Author(s):  
R. Vandenboom ◽  
R. W. Grange ◽  
M. E. Houston
Keyword(s):  
Isometric Force ◽  
Conditioning Stimulus ◽  
Force Production ◽  
Peak Force ◽  
Phosphate Content ◽  
Before And After ◽  
Skeletal Myosin ◽  
Fast Twitch Muscle ◽  
Isometric Twitch ◽  
Fast Twitch

Phosphate incorporation by the phosphorylatable light chains (P-LC) of myosin is associated with isometric twitch force potentiation in intact fast-twitch muscle. The purpose of this study was to examine the association between myosin P-LC phosphorylation and force potentiation at higher stimulation frequencies (1-150 Hz) using mouse extensor digitorum longus (EDL) muscles at 25 degrees C. Peak isometric force and the peak rate of isometric force development (+dF/dtmax) were measured at selected test frequencies before and after the application of a 5-Hz 20-s conditioning stimulation known to increase P-LC phosphate content. Associated with a ninefold elevation in myosin P-LC phosphate content (to 0.72 mol phosphate/mol P-LC), +dF/dtmax was increased at all test frequencies (mean 27%, range 20-37%). After the conditioning stimulus, peak isometric force was increased by approximately 15% for frequencies 1-15 Hz. However, at 20-150 Hz, the increase in +dF/dtmax was not associated with force potentiation, since peak force was diminished by 5-40%. These data reveal that the stimulation frequency limit for the potentiation of peak force production associated with myosin P-LC phosphorylation is < 20 Hz in mouse EDL at 25 degrees C. Furthermore, the data suggest that increases in the rate constant describing the rate of cross-bridge transition from a non-force-generating to a force-generating state mediated by myosin P-LC phosphorylation may be responsible for the general increase in +dF/dtmax and for the force potentiation at 1-15 Hz.

Decay of Ca2+ and force transients in fast- and slow-twitch skeletal muscles from the rat, mouse and Etruscan shrew.

1998 ◽  
Vol 201 (3) ◽  
pp. 375-384 ◽  
Author(s):  
P Wetzel ◽  
G Gros
Keyword(s):  
Skeletal Muscles ◽  
Muscle Relaxation ◽  
Muscle Fibres ◽  
Fura 2 ◽  
Single Twitch ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
The Right ◽  
Fast Twitch

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 pCa&shy;tension curve, which is shifted to the right compared with that of slow-twitch muscle.

scholarly journals Redox modulation of maximum force production of fast-and slow-twitch skeletal muscles of rats and mice

2001 ◽  
Vol 90 (3) ◽  
pp. 832-838 ◽  
Author(s):  
David R. Plant ◽  
Paul Gregorevic ◽  
David A. Williams ◽  
Gordon S. Lynch
Keyword(s):  
Skeletal Muscles ◽  
Isometric Force ◽  
Force Production ◽  
Dependent Manner ◽  
Redox Modulation ◽  
History Of ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Rats And Mice ◽  
Isometric Force Production

We used intact fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles from rats and mice to test the hypothesis that exogenous application of an oxidant would increase maximum isometric force production (Po) of slow-twitch muscles to a greater extent than fast-twitch skeletal muscles. Exposure to an oxidant, hydrogen peroxide (H2O2; 100 μM to 5 mM, 30 min), affected Po of rat muscles in a time- and dose-dependent manner. Po of rat soleus muscles was increased by 8 ± 1 (SE) and 14 ± 1% ( P < 0.01) after incubation with 1 and 5 mM H2O2, respectively, whereas in mouse soleus muscles Po was only increased after incubation with 500 μM H2O2. Po of rat EDL muscles was affected by H2O2 biphasically; initially there was a small increase (3 ± 1%), but then Po diminished significantly after 30 min of treatment. In contrast, all concentrations of H2O2 tested decreased Po of mouse EDL muscles. A reductant, dithiothreitol (DTT; rat = 10 mM, mouse = 1 mM), was added to quench H2O2, and it reversed the potentiation in Po in rat soleus but not in rat EDL muscles or in any H2O2-treated mouse muscles. After prolonged equilibration (30 min) with 5 mM H2O2 without prior activation, Po was potentiated in rat soleus but not EDL muscles, demonstrating that the effect of oxidation in the soleus muscles was also dependent on the activation history of the muscle. The results of these experiments demonstrate that Po of both slow- and fast-twitch muscles from rats and mice is modified by redox modulation, indicating that maximum Po of mammalian skeletal muscles is dependent on oxidation.

Glutamine synthetase induction by glucocorticoids is preserved in skeletal muscle of aged rats

1996 ◽  
Vol 271 (6) ◽  
pp. E1061-E1066 ◽  
Author(s):  
D. Meynial-Denis ◽  
M. Mignon ◽  
A. Miri ◽  
J. Imbert ◽  
E. Aurousseau ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glutamine Synthetase ◽  
Skeletal Muscles ◽  
Female Rats ◽  
Mrna Levels ◽  
Aged Rats ◽  
Adult Rats ◽  
Adult Age ◽  
Slow Twitch ◽  
Fast Twitch

Glutamine synthetase (GS) is a glucocorticoid-inducible enzyme that has a key role for glutamine synthesis in muscle. We hypothesized that the glucocorticoid induction of GS could be altered in aged rats, because alterations in the responsiveness of some genes to glucocorticoids were reported in aging. We compared the glucocorticoid-induced GS in fast-twitch and slow-twitch skeletal muscles (tibialis anterior and soleus, respectively) and heart from adult (age 6-8 mo) and aged (age 22 mo) female rats. All animals received dexamethasone (Dex) in their drinking water (0.77 +/- 0.10 and 0.80 +/- 0.08 mg/day per adult and aged rat, respectively) for 5 days. Dex caused an increase in both GS activity and GS mRNA in fast-twitch and slow-twitch skeletal muscles from adult and aged rats. In contrast, Dex increased GS activity in heart of adult rats, without any concomitant change in GS mRNA levels. Furthermore, Dex did not affect GS activity in aged heart. Thus the responsiveness of GS to an excess of glucocorticoids is preserved in skeletal muscle but not in heart from aged animals.

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.

Electrolytes in slow and fast muscle fibers of humans at rest and with dynamic exercise

1983 ◽  
Vol 245 (1) ◽  
pp. R25-R31 ◽  
Author(s):  
G. Sjogaard
Keyword(s):  
Skeletal Muscles ◽  
Vastus Lateralis ◽  
Fiber Types ◽  
Triceps Brachii ◽  
Sodium Potassium ◽  
Mean Values ◽  
Fiber Composition ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Muscle Fiber Membrane

Sodium, potassium, and magnesium were analyzed in human slow-twitch (ST) and fast-twitch (FT) skeletal muscles. In contrast to other species, no relation was found between fiber composition and electrolyte distribution. In soleus (S), vastus lateralis (VL), and triceps brachii (TB) the overall mean values for 6 men and 6 women were 44 mmol K/100 g dry wt and 11 mmol Na/100 g dry wt; the intracellular concentrations were 161 mmol K/l and 26 mmol Na/l with no differences between the muscles. Analysis of fragments of single ST and FT fibers from each of the muscles also showed no difference between the fiber types in Na and K content. Small differences were seen between the muscles with regard to Mg, but these were not related to fiber composition compared with other species. During exercise to exhaustion (3 bouts of bicycling for 3 min at 325-395 W, 6 men) the extracellular electrolyte concentrations for Na, K, and Mg increased from 134 to 140, 4.5 to 5.8, and 0.75 to 0.87 mmol/l, respectively (P less than 0.05). In VL Na content increased from 9.8 to 16.5 mmol/100 g dry wt, while intracellular [Na] remained constant. In contrast, intracellular [K] decreased from 161 to 141 mmol/l (P less than 0.05). No such changes occurred in TB. In concert with other studies the present changes in electrolytes in the working muscles indicate that muscle fatigue may be related to changes at the muscle fiber membrane.

Recovery in skeletal muscle contractile function after prolonged hindlimb immobilization

1985 ◽  
Vol 59 (3) ◽  
pp. 916-923 ◽  
Author(s):  
R. H. Fitts ◽  
C. J. Brimmer
Keyword(s):  
Contractile Function ◽  
Vastus Lateralis ◽  
Weight Ratio ◽  
Contractile Properties ◽  
Shortening Velocity ◽  
Slow Twitch ◽  
Isometric Twitch ◽  
Fast Twitch ◽  
Muscle Contractile

Contractile properties of slow-twitch soleus (SOL), fast-twitch extensor digitorum longus (EDL), and fast-twitch superficial region of the vastus lateralis were determined in vitro (22 degrees C) in rats remobilized after prolonged (3 mo) hindlimb immobilization (IM). For all muscles the muscle-to-body weight ratio was significantly depressed by IM, and the ratios failed to completely recover even after 90 days. The contractile properties of the fast-twitch muscles were less affected by IM than the slow-twitch SOL. The IM shortened the SOL isometric twitch duration due to a reduced contraction and half-relaxation time. These parameters returned to control levels by the 14th day of recovery. Peak tetanic tension (Po, g/cm2) declined with IM by 46% in the SOL but showed no significant change in the fast-twitch muscles. After IM the SOL Po (g/cm2) recovered to control values by 28 days. The recovery of Po in absolute units (g) was considerably slower and did not return to control levels until 60 (SOL) to 90 (EDL) days. The maximum shortening velocity was not altered by IM in any of the muscles studied. These results demonstrate that both fast- and slow-twitch skeletal muscles possess the ability to completely recover normal contractile function following prolonged periods of hindlimb IM.

ATP depletion in slow-twitch red muscle of rat

1987 ◽  
Vol 253 (3) ◽  
pp. C426-C432 ◽  
Author(s):  
D. M. Whitlock ◽  
R. L. Terjung
Keyword(s):  
Adenine Nucleotide ◽  
Atp Depletion ◽  
Cellular Events ◽  
Contraction Condition ◽  
Red Muscle ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Fast Twitch

Rat slow-twitch muscle, in contrast to fast-twitch muscle, maintains its ATP content near normal during intense stimulation conditions that produce rapid fatigue. An extensive depletion of adenine nucleotide content by the deamination of AMP to IMP + NH3, typical of fast-twitch muscle, does not occur. We evaluated whether this response of slow-twitch muscle could be simply due to failure of synaptic transmission or related to cellular conditions influencing enzyme activity. Stimulation of soleus muscles in situ via the nerve or directly in the presence of curare at 120 tetani/min for 3 min resulted in extensive fatigue but normal ATP contents. Thus the lack of ATP depletion must be related to cellular events distal to neuromuscular transmission. Even nerve and direct muscle stimulation (with curare) during ischemia did not cause a large depletion of ATP or a large elevation of lactate content (12.0 +/- 0.7 mumol/g), even though the decline in tension was essentially complete. However, if the same tension decline during ischemia was prolonged by stimulating for 10 min at 12 tetani/min a large decrease in ATP (2.24 +/- 0.09 mumol/g) and increase in IMP (2.47 +/- 0.16 mumol/g) and lactate (30.4 +/- 2.0 mumol/g) content occurred. Thus adenine nucleotide deamination to IMP can occur in slow-twitch muscle during specific contraction conditions. The cellular events leading to the activation of AMP deaminase require an intense contraction condition and may be related to acidosis caused by a high lactate content.

scholarly journals Comparative analysis of the transcriptomes of EDL, psoas, and soleus muscles from mice

BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Pabodha Hettige ◽  
Uzma Tahir ◽  
Kiisa C. Nishikawa ◽  
Matthew J. Gage
Keyword(s):  
Skeletal Muscles ◽  
Striated Muscle ◽  
Fiber Type ◽  
Expression Patterns ◽  
Fiber Types ◽  
Muscle Adaptation ◽  
Myosin Heavy Chain Isoform ◽  
Genes Encoding ◽  
Slow Twitch ◽  
Fast Twitch

Abstract Background Individual skeletal muscles have evolved to perform specific tasks based on their molecular composition. In general, muscle fibers are characterized as either fast-twitch or slow-twitch based on their myosin heavy chain isoform profiles. This approach made sense in the early days of muscle studies when SDS-PAGE was the primary tool for mapping fiber type. However, Next Generation Sequencing tools permit analysis of the entire muscle transcriptome in a single sample, which allows for more precise characterization of differences among fiber types, including distinguishing between different isoforms of specific proteins. We demonstrate the power of this approach by comparing the differential gene expression patterns of extensor digitorum longus (EDL), psoas, and soleus from mice using high throughput RNA sequencing. Results EDL and psoas are typically classified as fast-twitch muscles based on their myosin expression pattern, while soleus is considered a slow-twitch muscle. The majority of the transcriptomic variability aligns with the fast-twitch and slow-twitch characterization. However, psoas and EDL exhibit unique expression patterns associated with the genes coding for extracellular matrix, myofibril, transcription, translation, striated muscle adaptation, mitochondrion distribution, and metabolism. Furthermore, significant expression differences between psoas and EDL were observed in genes coding for myosin light chain, troponin, tropomyosin isoforms, and several genes encoding the constituents of the Z-disk. Conclusions The observations highlight the intricate molecular nature of skeletal muscles and demonstrate the importance of utilizing transcriptomic information as a tool for skeletal muscle characterization.

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