scholarly journals Effects of glucose on contractile function, [Ca2+]i, and glycogen in isolated mouse skeletal muscle

2002 ◽  
Vol 282 (6) ◽  
pp. C1306-C1312 ◽  
Author(s):  
Ingrid Helander ◽  
Håkan Westerblad ◽  
Abram Katz
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Contractile Function ◽  
Extensor Digitorum ◽  
Fluorescence Ratio ◽  
Tetanic Force ◽  
Mouse Skeletal Muscle ◽  
Control Value ◽  
Extracellular Glucose ◽  
Initial Force

Extensor digitorum longus muscles were stimulated to contract to fatigue and allowed to recover for 2 h in the absence or presence of 5.5 or 11 mM extracellular glucose. This was followed by a second fatigue run, which ended when the absolute force was the same as at the end of the first run. During the first fatigue run, the fluorescence ratio for indo 1 increased [reflecting an increase in myoplasmic free Ca2+ concentration ([Ca2+]i)] during the initial tetani, peaking at ∼115% of the first tetanic value, followed by a continuous decrease to ∼90% at fatigue. During the first fatigue run, myofibrillar Ca2+ sensitivity was significantly decreased. During the second run, the number of tetani was 57 ± 6% of initial force in muscles that recovered in the absence of glucose and 110 ± 6 and 119 ± 2% of initial force in muscles that recovered in 5.5 and 11 mM glucose, respectively. Fluorescence ratios during the first, peak, and last tetani did not differ significantly between the first and second fatigue runs during any of the three conditions. Glycogen decreased by almost 50% during the first fatigue run and did not change further after recovery in the absence of glucose. After recovery in the presence of 5.5 and 11 mM glucose, glycogen increased 32 and 42% above the nonstimulated control value ( P < 0.01). These data demonstrate that extracellular glucose delays the decrease of tetanic force and [Ca2+]i during fatiguing stimulation and that glycogen supercompensation following contraction can occur in the absence of insulin.

Increased submaximal insulin-stimulated glucose uptake in mouse skeletal muscle after treadmill exercise

2006 ◽  
Vol 101 (5) ◽  
pp. 1368-1376 ◽  
Author(s):  
Taku Hamada ◽  
Edward B. Arias ◽  
Gregory D. Cartee
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Uptake ◽  
Extensor Digitorum Longus ◽  
Treadmill Exercise ◽  
Genetically Modified ◽  
Extensor Digitorum ◽  
Exercise Protocol ◽  
Mouse Skeletal Muscle ◽  
Prior Exercise

The primary purpose of this study was to determine the effect of prior exercise on insulin-stimulated glucose uptake with physiological insulin in isolated muscles of mice. Male C57BL/6 mice completed a 60-min treadmill exercise protocol or were sedentary. Paired epitrochlearis, soleus, and extensor digitorum longus (EDL) muscles were incubated with [3H]-2-deoxyglucose without or with insulin (60 μU/ml) to measure glucose uptake. Insulin-stimulated glucose uptake for paired muscles was calculated by subtracting glucose uptake without insulin from glucose uptake with insulin. Muscles from other mice were assessed for glycogen and AMPK Thr172 phosphorylation. Exercised vs. sedentary mice had decreased glycogen in epitrochlearis (48%, P < 0.001), soleus (51%, P < 0.001), and EDL (41%, P < 0.01) and increased AMPK Thr172 phosphorylation ( P < 0.05) in epitrochlearis (1.7-fold), soleus (2.0-fold), and EDL (1.4-fold). Insulin-independent glucose uptake was increased 30 min postexercise vs. sedentary in the epitrochlearis (1.2-fold, P < 0.001), soleus (1.4-fold, P < 0.05), and EDL (1.3-fold, P < 0.01). Insulin-stimulated glucose uptake was increased ( P < 0.05) ∼85 min after exercise in the epitrochlearis (sedentary: 0.266 ± 0.045 μmol·g−1·15 min−1; exercised: 0.414 ± 0.051) and soleus (sedentary: 0.102 ± 0.049; exercised: 0.347 ± 0.098) but not in the EDL. Akt Ser473 and Akt Thr308 phosphorylation for insulin-stimulated muscles did not differ in exercised vs. sedentary. These results demonstrate enhanced submaximal insulin-stimulated glucose uptake in the epitrochlearis and soleus of mice 85 min postexercise and suggest that it will be feasible to probe the mechanism of enhanced postexercise insulin sensitivity by using genetically modified mice.

Endothelial cell products alter mammalian skeletal muscle function in vitro

1995 ◽  
Vol 73 (6) ◽  
pp. 736-741 ◽  
Author(s):  
C. L. Murrant ◽  
J. K. Barclay
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Mammalian Skeletal Muscle ◽  
Skeletal Muscle Function ◽  
Endothelin 1 ◽  
Control Value ◽  
Endothelin 3 ◽  
Fast Twitch

We tested the hypothesis that endothelin and nitric oxide (NO) alter the force developed by fast-twitch and slow-twitch mammalian skeletal muscle, using a mouse skeletal muscle preparation trimmed to approximately 50% of the original diameter to decrease diffusion distances. We suspended trimmed soleus (SOL) and extensor digitorum longus (EDL) muscles in Krebs–Henseleit buffer (27 °C; pH 7.4) gassed with 95% O2 – 5% CO2. Muscles were stimulated once every 90 s for 500 ms at 50 Hz for SOL and 100 Hz for EDL. The force developed by trimmed SOL was 223.8 ± 9.1 mN/mm2 and by EDL was 247.3 ± 9.4 mN/mm2. Endothelin 1 (ET-1) had no effect on EDL but significantly accelerated the rate of decrease of developed force of SOL at concentrations of 10−10 mol/L and higher within 10 contractions. When ET-1 was removed, force returned toward control value. Endothelin 3 (ET-3) had no effect on either muscle. S-Nitroso-N-acetylpenicillamine (SNAP), a source of NO, increased developed force over time in both muscles, with a threshold of 10−6 mol/L. The effect was evident within 5 contractions in both muscles. Force remained elevated above control values after the removal of SNAP. Thus ET-1 attenuated and NO amplified mammalian skeletal muscle function.Key words: soleus, extensor digitorum longus, tetanic contractions, endothelin 1, endothelin 3, S-nitroso-N-acetylpenicillamine.

Human growth hormone treatment of hypophysectomized rats increases the proportion of type-1 fibres in skeletal muscle

1989 ◽  
Vol 123 (3) ◽  
pp. 429-NP ◽  
Author(s):  
C. M. Ayling ◽  
B. H. Moreland ◽  
J. M. Zanelli ◽  
D. Schulster
Keyword(s):  
Skeletal Muscle ◽  
Fibre Type ◽  
Extensor Digitorum Longus ◽  
Human Growth ◽  
Hormone Treatment ◽  
Pituitary Hormones ◽  
Extensor Digitorum ◽  
Replacement Treatment ◽  
Hypophysectomized Rats

ABSTRACT The studies describe alterations after hypophysectomy in the proportion of the type-1 and type-2 fibres in rat skeletal muscles, and the effects of replacement treatment with pituitary human (h) GH. Cytochemical analysis of myosin ATPase, succinate dehydrogenase and lactate dehydrogenase activities in sections of rat hind limb muscles were used as markers of fibre type and revealed that hypophysectomy reduced the proportion of type-1 fibres by 50% in soleus and in extensor digitorum longus muscles. This reduction in the proportion of type-1 fibres was accompanied by the appearance of transitional fibres (type 2C/1B). Following seven daily injections of hGH (60 mIU/day) to hypophysectomized rats, the proportion of type-1 fibres in both soleus and in extensor digitorum longus was increased with a concomitant reduction in the number of transitional fibres. After 11 days of treatment, all these transitional fibres had reverted back to type-1 fibres. Only hGH was observed to elicit this effect; injections of other pituitary hormones had no effect on the proportions of these transitional fibres. These alterations in fibre type occurred more rapidly than the changes reported after prolonged electrical stimulation of muscle or following extended exercise. These findings suggest that hypophysectomy and GH injection can result in a rapid alteration in the fibre composition of skeletal muscle, which may have important implications in terms of the resistance to fatigue and speed of contraction of the muscle. Journal of Endocrinology (1989) 123, 429–435

scholarly journals Identification in skeletal muscle of a distinct extracellular pool of amino acids, and its role in protein synthesis

1971 ◽  
Vol 121 (5) ◽  
pp. 817-827 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Kinetics Of

1. The kinetics of radioactive labelling of extra- and intra-cellular amino acid pools and protein of the extensor digitorum longus muscle were studied after incubations with radioactive amino acids in vitro. 2. The results indicated that an extracellular pool could be defined, the contents of which were different from those of the incubation medium. 3. It was concluded that amino acids from the extracellular pool, as defined in this study, were incorporated directly into protein.

Spaceflight on STS-48 and earth-based unweighting produce similar effects on skeletal muscle of young rats

1993 ◽  
Vol 74 (5) ◽  
pp. 2161-2165 ◽  
Author(s):  
M. E. Tischler ◽  
E. J. Henriksen ◽  
K. A. Munoz ◽  
C. S. Stump ◽  
C. R. Woodman ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Space Shuttle ◽  
Weight Bearing ◽  
Similar Rate ◽  
Extensor Digitorum ◽  
Hindlimb Suspension ◽  
Albino Rats ◽  
Sprague Dawley ◽  
Ambient Temperatures

Our knowledge of the effects of unweighting on skeletal muscle of juvenile rapidly growing rats has been obtained entirely by using hindlimb-suspension models. No spaceflight data on juvenile animals are available to validate these models of simulated weightlessness. Therefore, eight 26-day-old female Sprague-Dawley albino rats were exposed to 5.4 days of weightlessness aboard the space shuttle Discovery (mission STS-48, September 1991). An asynchronous ground control experiment mimicked the flight cage condition, ambient shuttle temperatures, and mission duration for a second group of rats. A third group of animals underwent hindlimb suspension for 5.4 days at ambient temperatures. Although all groups consumed food at a similar rate, flight animals gained a greater percentage of body mass per day (P < 0.05). Mass and protein data showed weight-bearing hindlimb muscles were most affected, with atrophy of the soleus and reduced growth of the plantaris and gastrocnemius in both the flight and suspended animals. In contrast, the non-weight-bearing extensor digitorum longus and tibialis anterior muscles grew normally. Earlier suspension studies showed that the soleus develops an increased sensitivity to insulin during unweighting atrophy, particularly for the uptake of 2-[1,2–3H]deoxyglucose. Therefore, this characteristic was studied in isolated muscles within 2 h after cessation of spaceflight or suspension. Insulin increased uptake 2.5- and 2.7-fold in soleus of flight and suspended animals, respectively, whereas it increased only 1.6-fold in control animals. In contrast, the effect of insulin was similar among the three groups for the extensor digitorum longus, which provides a control for potential systemic differences in the animals.

Muscle fatigue in frog semitendinosus: role of intracellular pH

1992 ◽  
Vol 262 (6) ◽  
pp. C1507-C1512 ◽  
Author(s):  
L. V. Thompson ◽  
E. M. Balog ◽  
R. H. Fitts
Keyword(s):  
Intracellular Ph ◽  
Contractile Function ◽  
Resting Membrane Potential ◽  
Slow Phase ◽  
Tetanic Force ◽  
Average Value ◽  
Highly Correlated ◽  
Initial Force ◽  
The Relationship

The purpose of this study was to utilize glass microelectrodes to characterize the intracellular pH (pHi) before and during recovery from fatigue in the frog semitendinosus (ST) muscle. A second objective was to evaluate the relationship between pHi and contractile function. The frog ST muscle (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. Peak tetanic force (Po) was reduced to 8.5% of initial force and recovered in a biphasic manner, returning to the resting value by 40 min. Resting pHi was 7.00 +/- 0.02 (n = 37) and declined with fatigue to an average value of 6.42 at 3 min of recovery. During recovery pHi significantly increased and by 25 min had returned to the prefatigue value. The pHi recovery was highly correlated to the slow phase of Po recovery (r = 0.98, P less than 0.001). The mean resting membrane potential was -78 +/- 1.0 mV (n = 42) and at 3 min of recovery was depolarized to -67 +/- 4 mV. Both the peak rate of twitch force development (+dP/dt) (r = 0.99, P less than 0.001) and decline (-dP/dt) (r = 0.94, P less than 0.014) were highly correlated to pHi during the slow phase of recovery. Contraction time (CT) and one-half relaxation time (1/2RT) increased significantly and recovered exponentially. The recovery of CT and 1/2RT were both significantly correlated to pHi (r = -0.93, P less than 0.001 and r = -0.86, P less than 0.001 for CT and 1/2RT, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in contractile properties of skeletal muscle during developmentally programmed atrophy and death

2002 ◽  
Vol 282 (6) ◽  
pp. C1270-C1277 ◽  
Author(s):  
Lawrence M. Schwartz ◽  
Robert L. Ruff
Keyword(s):  
Skeletal Muscle ◽  
Contractile Function ◽  
Adult Emergence ◽  
Calcium Sensitivity ◽  
Resting Potential ◽  
Skeletal Muscle Atrophy ◽  
Tetanic Force ◽  
Death Phase ◽  
Hill Coefficients ◽  
Fiber Organization

Skeletal muscle atrophy and death are protracted processes that accompany aging and pathological insults in mammals. The intersegmental muscles (ISMs) from the tobacco hawkmoth Manduca sexta are composed of giant fibers that undergo distinct hormonally-regulated programs of atrophy and death at the end of metamorphosis. Atrophy occurs during the 3 days preceding adult emergence and results in a 40% reduction of mass, whereas death takes place during the subsequent 30 h and results in the complete loss of the fibers. There are no significant changes in tetanic force or calcium sensitivity in skinned fiber preparations during atrophy. However, the size of caffeine-induced contractions fell by about 50%. With the onset of the death phase, dramatic reductions occur in ISM: tetanic force, twitch amplitude, resting potential, caffeine-induced contractions, calcium sensitivity, and Hill coefficients. Several lines of evidence suggest that ISM atrophy is caused by an increase in protein turnover without significant modification of fiber organization. In contrast, ISM death is accompanied by disorganization of the contractile apparatus and concomitant loss of contractile function.

scholarly journals Purine biosynthesis de novo in rat skeletal muscle

1983 ◽  
Vol 216 (3) ◽  
pp. 605-610 ◽  
Author(s):  
T G Sheehan ◽  
E R Tully
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
De Novo ◽  
Adenine Nucleotides ◽  
Extensor Digitorum ◽  
Purine Biosynthesis ◽  
Rat Skeletal Muscle ◽  
Purine Synthesis ◽  
Longus Muscle ◽  
Isolated Rat

Purine biosynthesis by the ‘de novo’ pathway was demonstrated in isolated rat extensor digitorum longus muscle with [1-14C]glycine, [3-14C]serine and sodium [14C]formate as nucleotide precursors. Evidence is presented which suggests that the source of glycine and serine for purine biosynthesis is extracellular rather than intracellular. The relative incorporation rates of the three precursors were formate greater than glycine greater than serine. Over 85% of the label from formate and glycine was recovered in the adenine nucleotides, principally ATP. Azaserine markedly inhibited purine biosynthesis from both formate and glycine. Cycloserine inhibited synthesis from serine, but not from formate. Adenine, hypoxanthine and adenosine markedly inhibited purine synthesis from sodium [14C]formate.

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