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.

Myosin light chain phosphorylation-dephosphorylation in mammalian skeletal muscle

1982 ◽  
Vol 242 (3) ◽  
pp. C234-C241 ◽  
Author(s):  
D. R. Manning ◽  
J. T. Stull
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Extensor Digitorum Longus ◽  
Myosin Light Chain ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Mammalian Skeletal Muscle ◽  
Phosphate Content ◽  
Longus Muscle ◽  
Fast Twitch

Phosphorylation of the myosin light chain 2 (LC2) subunit was examined in rat fast-twitch and slow-twitch skeletal muscles in response to repetitive stimulation at 23 and 35 degrees C and on incubation of fast-twitch skeletal muscle with isoproterenol. After a 1-s tetany at 35 degrees C, LC2 phosphate content in extensor digitorum longus muscle increased rapidly and transiently from 0.21 to 0.51 mol phosphate/mol LC2. This pattern of phosphorylation was similar to that observed at 23 degrees C. Increases in LC2 phosphate content were dependent on the frequency and duration of stimulation. In soleus muscle LC2 phosphate content was minimal following a 1-s tetany but increased markedly following more prolonged tetanies. On incubation of extensor digitorum longus muscle with isoproterenol (20 microM), LC2 phosphate content did not change, whereas phosphorylase a levels increased. A positive correlation existed between LC2 phosphate content and potentiation of peak twitch tension in both types of muscles, suggesting a physiological function for LC2 phosphorylation.

scholarly journals When phosphorylated at Thr148, the β2-subunit of AMP-activated kinase does not associate with glycogen in skeletal muscle

2016 ◽  
Vol 311 (1) ◽  
pp. C35-C42 ◽  
Author(s):  
Hongyang Xu ◽  
Noni T. Frankenberg ◽  
Graham D. Lamb ◽  
Paul R. Gooley ◽  
David I. Stapleton ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Carbohydrate Binding ◽  
Binding Function ◽  
Physiological Relevance ◽  
Amp Activated Protein Kinase ◽  
Fast Twitch ◽  
Stimulation Of

The 5′-AMP-activated protein kinase (AMPK), a heterotrimeric complex that functions as an intracellular fuel sensor that affects metabolism, is activated in skeletal muscle in response to exercise and utilization of stored energy. The diffusibility properties of α- and β-AMPK were examined in isolated skeletal muscle fiber segments dissected from rat fast-twitch extensor digitorum longus and oxidative soleus muscles from which the surface membranes were removed by mechanical dissection. After the muscle segments were washed for 1 and 10 min, ∼60% and 75%, respectively, of the total AMPK pools were found in the diffusible fraction. After in vitro stimulation of the muscle, which resulted in an ∼80% decline in maximal force, 20% of the diffusible pool became bound in the fiber. This bound pool was not associated with glycogen, as determined by addition of a wash step containing amylase. Stimulation of extensor digitorum longus muscles resulted in 28% glycogen utilization and a 40% increase in phosphorylation of the downstream AMPK target acetyl carboxylase-CoA. This, however, had no effect on the proportion of total β2-AMPK that was phosphorylated in whole muscle homogenates measured by immunoprecipitation. These findings suggest that, in rat skeletal muscle, β2-AMPK is not associated with glycogen and that activation of AMPK by muscle contraction does not dephosphorylate β2-AMPK. These findings question the physiological relevance of the carbohydrate-binding function of β2-AMPK in skeletal muscle.

Glycogenesis and glyconeogenesis in skeletal muscle: effects of pH and hormones

1990 ◽  
Vol 258 (4) ◽  
pp. E693-E700 ◽  
Author(s):  
A. Bonen ◽  
J. C. McDermott ◽  
M. H. Tan
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Extensor Digitorum Longus ◽  
Muscle Fibers ◽  
Extensor Digitorum ◽  
Effects Of Ph ◽  
Slow Twitch ◽  
Highly Correlated ◽  
Fast Twitch

We examined the effects of selected hormones and pH on the rates of glyconeogenesis (L-[U-14C]-lactate----glycogen) and glycogenesis (D-[U-14C]glucose----glycogen) in mouse fast-twitch (FT) and slow-twitch muscles incubated in vitro (37 degrees C). Glyconeogenesis and glycogenesis increased linearly with increasing concentrations of lactate (5-20 mM) and glucose (2.5-10 mM), respectively, in both muscles. Glyconeogenesis was approximately three- to fourfold greater in the extensor digitorum longus (EDL) than in the soleus, whereas basal glycogenesis was twofold greater in the soleus muscle than in the EDL. Lactate accounted for up to 5% of the glycogen formed in the soleus and up to 32% in the EDL relative to the rates of glycogenesis (i.e., 5 mM glucose + 10 nM insulin) in each muscle. Corticosterone (10(-12)-10(-6) M) failed to alter glyconeogenesis, whereas this hormone reduced glycogenesis. Insulin (10 nM) markedly stimulated glycogenesis but failed to stimulate glyconeogenesis. The rates of both glycogenesis and glyconeogenesis were pH sensitive, with optimal rates at pH 6.5-7.0 in both muscles. Glyconeogenesis increased by 49% in the soleus and by 39% EDL at pH 6.5 compared with pH 7.4. Glycogenesis increased in the soleus (SOL) and EDL in the absence (SOL: +22%; EDL: +52%) and presence of insulin (SOL: +22%; EDL: +51%) at pH 6.5 when compared with pH 7.4. In additional experiments with the perfused rat hindquarter, rates of glyconeogenesis were shown to be highly correlated with proportion of FT muscle fibers in a muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Positive inotropism in mammalian skeletal muscle in vitro during and after fatigue

2004 ◽  
Vol 82 (4) ◽  
pp. 249-261 ◽  
Author(s):  
S A Reading ◽  
C L Murrant ◽  
J K Barclay
Keyword(s):  
Carbon Dioxide ◽  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Vehicle Control ◽  
Extensor Digitorum ◽  
Mammalian Skeletal Muscle ◽  
Muscle Contractility ◽  
Cyclic Monophosphate ◽  
Camp Analog

We tested the hypothesis that positive inotropic factors decrease fatigue and improve recovery from fatigue in mammalian skeletal muscle in vitro. To induce fatigue, we stimulated mouse soleus and extensor digitorum longus (EDL) to perform isometric tetanic contractions (50 impulses·s–1 for 0.5 s) at 6 contractions·min–1 for 60 min in soleus and 3 contractions·min–1 for 20 min in EDL. Muscles were submerged in Krebs–Henseleit bicarbonate solution (Krebs) at 27 °C gassed with 95% nitrogen – 5% carbon dioxide (anoxia). Before and for 67 min after the fatigue period, muscles contracted at 0.6 contractions·min–1 in 95% oxygen – 5% carbon dioxide (hyperoxia). We added a permeable cAMP analog (N6, 2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate at 10–3 mol·L–1 (dcAMP)), caffeine (2×10–3 mol·L–1, or Krebs as vehicle control at 25 min before, during, or at the end of the fatigue period. In soleus and EDL, both challenges added before fatigue significantly increased developed force but only caffeine increased developed force when added during the fatigue period. At the end of fatigue, the decrease in force in challenged muscles was equal to or greater than in controls so that the force remaining was the same or less than in controls. EDL challenged with dcAMP or caffeine at any time recovered more force than controls. In soleus, caffeine improved recovery except when added before fatigue. With dcAMP added to soleus, recovery was better after challenges at 10 min and the end of the fatigue period. Thus, increased intracellular concentrations of cAMP and (or) Ca2+ did not decrease fatigue in either muscle but improved recovery from fatigue in EDL and, in some conditions, in soleus.Key words: skeletal muscle contractility, isometric tetanic contractions, hyperoxia, anoxia.

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.

Effects of exercise and glycogen depletion on glyconeogenesis in muscle

1994 ◽  
Vol 76 (4) ◽  
pp. 1753-1758 ◽  
Author(s):  
A. Bonen ◽  
D. A. Homonko
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Extensor Digitorum Longus ◽  
Treadmill Exercise ◽  
Glycogen Depletion ◽  
Epinephrine Injection ◽  
Slow Twitch ◽  
Glycogen Repletion ◽  
Fast Twitch

In the present study, we investigated the hypotheses that 1) skeletal muscle glyconeogenesis will increase after exercise, 2) greater changes in glyconeogenesis will be observed after exercise in fast-twitch muscles than in slow-twitch muscles, and 3) glycogen repletion will reduce the rates of glyconeogenesis. Mouse soleus and extensor digitorum longus (EDL) glycogen depots were reduced to the same levels by treadmill exercise (60 min) or epinephrine injection (75 micrograms/100 g body wt ip). Untreated animals were used as controls. We were able to prevent glycogen repletion by incubating muscles in vitro with sorbitol (75 mM) and to increase glycogen concentrations in vitro by incubating muscles with glucose (75 mM). The experimental results showed that glyconeogenesis was increased by exercise (EDL, +51%; soleus, +82%) when glycogen levels were kept low. When glycogen depots were increased, the rate of glyconeogenesis was lowered in the exercised EDL (P < 0.05) but not in the soleus (P > 0.05). Reductions in muscle glycogen by epinephrine did not change the rate of glyconeogenesis in EDL, either when glycogen depots were kept low or were repleted (P > 0.05). In contrast, in the soleus, epinephrine-induced reductions in glycogen did stimulate glyconeogenesis (P < 0.05). Analyses in EDL showed that in nonexercised muscles glycogen concentrations were minimally effective in altering the rates of glyconeogenesis. A 30% decrement in glycogen increased glyconeogenesis by 5% in resting muscles, whereas the same decrement increased glyconeogenesis by 51% in exercised muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Regulation of total and myofibrillar protein breakdown in rat extensor digitorum longus and soleus muscle incubated flaccid or at resting length

1990 ◽  
Vol 267 (1) ◽  
pp. 37-44 ◽  
Author(s):  
P O Hasselgren ◽  
M Hall-Angerås ◽  
U Angerås ◽  
D Benson ◽  
J H James ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Total Protein ◽  
Extensor Digitorum Longus ◽  
Myofibrillar Protein ◽  
Extensor Digitorum ◽  
Protein Breakdown ◽  
Breakdown Rate ◽  
Net Production ◽  
Breakdown Rates

The present study characterized total and myofibrillar protein breakdown rates in a muscle preparation frequently used in vitro, i.e. incubated extensor digitorum longus (EDL) and soleus (SOL) muscles of young rats. Total and myofibrillar protein breakdown rates were assessed by determining net production by the incubated muscles of tyrosine and 3-methylhistidine (3-MH) respectively. Both amino acids were determined by h.p.l.c. Both total and myofibrillar protein breakdown rates were higher in SOL than in EDL muscles and were decreased by incubating the muscles maintained at resting length, rather than flaccid. After fasting for 72 h, total protein breakdown (i.e. tyrosine release) was increased by 73% and 138% in EDL muscles incubated flaccid and at resting length respectively. Net production of tyrosine by SOL muscle was not significantly altered by fasting. In contrast, myofibrillar protein degradation (i.e. 3-MH release) was markedly increased by fasting in both muscles. When tissue was incubated in the presence of 1 munit of insulin/ml, total protein breakdown rate was inhibited by 17-20%, and the response to the hormone was similar in muscles incubated flaccid or at resting length. In contrast, myofibrillar protein breakdown rate was not altered by insulin in any of the muscle preparations. The results support the concepts of individual regulation of myofibrillar and non-myofibrillar proteins and of different effects of various conditions on protein breakdown in different types of skeletal muscle. Thus determination of both tyrosine and 3-MH production in red and white muscle is important for a more complete understanding of protein regulation in skeletal muscle.

Extracellular hyperosmotic stress stimulates glucose uptake in incubated fast-twitch rat skeletal muscle

2013 ◽  
Vol 38 (6) ◽  
pp. 605-612 ◽  
Author(s):  
Chris M. Farlinger ◽  
Adrian J. Lui ◽  
Rose C. Harrison ◽  
Paul J. LeBlanc ◽  
Sandra J. Peters ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Energy Charge ◽  
Hyperosmotic Stress ◽  
Male Rats ◽  
Organ Bath ◽  
Mammalian Skeletal Muscle ◽  
Relative Water ◽  
Fast Twitch

The influence of hyperosmotic stress on glucose uptake, handling, and signaling processes remains unclear in mammalian skeletal muscle. Thus, the purpose of this study was to investigate alterations in glucose uptake and handling during extracellular hyperosmotic stress in isolated fast-twitch mammalian skeletal muscle. Using an established in vitro isolated whole-muscle model, extensor digitorum longus (EDL) muscles were dissected from male rats (4–6 weeks of age) and incubated (30–60 min) in an organ bath, containing Sigma Medium-199 with 8 mmol·L−1D-glucose, and mannitol was added to the targeted osmolalities (ISO, iso-osmotic, 290 mmol·kg−1; HYPER, hyperosmotic, 400 mmol·kg−1). Results demonstrate that relative water content decreased in HYPER. HYPER resulted in significant alterations in muscle metabolite concentrations (lower glycogen, elevated lactate, and glucose-6-phosphate), suggesting a decrease in energy charge. Glucose uptake was also found to be higher in HYPER, and AS160 (implicated in insulin- and contraction-mediated glucose uptake) was found to be significantly more phosphorylated in HYPER than in ISO after 30 min. In conclusion, glucose uptake and handling is altered with hyperosmotic extracellular stress in the fast-twitch EDL. The increases in glucose uptake might be facilitated through alterations in AS160 signaling after 30 to 60 min of osmotic stress.

No effects of lifelong creatine supplementation on sarcopenia in senescence-accelerated mice (SAMP8)

2005 ◽  
Vol 289 (2) ◽  
pp. E272-E277 ◽  
Author(s):  
Wim Derave ◽  
Bert O. Eijnde ◽  
Monique Ramaekers ◽  
Peter Hespel
Keyword(s):  
Muscle Mass ◽  
Muscle Function ◽  
Extensor Digitorum Longus ◽  
Creatine Supplementation ◽  
Skeletal Muscle Function ◽  
Muscle Types ◽  
Metabolic Properties ◽  
Fast Twitch ◽  
Senescence Accelerated Mice

Oral creatine supplementation can acutely ameliorate skeletal muscle function in older humans, but its value in the prevention of sarcopenia remains unknown. We evaluated the effects of lifelong creatine supplementation on muscle mass and morphology, contractility, and metabolic properties in a mouse model of muscle senescence. Male senescence-accelerated mice (SAMP8) were fed control or creatine-supplemented (2% of food intake) diet from the age of 10 to 60 wk. Soleus and extensor digitorum longus muscles were tested for in vitro contractile properties, creatine content, and morphology at weeks 25 and 60. Both muscle types showed reduced phosphocreatine content at week 60 that could not be prevented by creatine. Accordingly, age-associated decline in muscle mass and contractility was not influenced by treatment. Aged soleus muscles had fewer and smaller fast-twitch glycolytic fibers irrespective of treatment received. It is concluded that lifelong creatine supplementation is no effective strategy to prevent sarcopenia in senescence-accelerated mice.

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