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.

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.

scholarly journals Skeletal-muscle growth and protein turnover

1975 ◽  
Vol 150 (2) ◽  
pp. 235-243 ◽  
Author(s):  
D J Millward ◽  
P J Garlick ◽  
R J C Stewart ◽  
D O Nnanyelugo ◽  
J C Waterlow
Keyword(s):  
Skeletal Muscle ◽  
Growth Rate ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Growth ◽  
Muscle Size ◽  
Synthesis Rate ◽  
Protein Breakdown ◽  
Breakdown Rate ◽  
Breakdown Rates

Because of turnover, protein synthesis and breakdown can each be involved in the regulation of the growth of tissue protein. To investigate the regulation of skeletal-muscle-protein growth we measured rates of protein synthesis and breakdown in growing rats during development on a good diet, during development on a marginally low-protein diet and during rehabilitation on a good diet after a period of severe protein deficiency. Rates of protein synthesis were measured in vivo with a constant intravenous infusion of [14C]tyrosine. The growth rate of muscle protein was measured and the rate of breakdown calculated as breakdown rate=synthesis rate-growth rate. These measurements showed that during development on a good diet there was a fall with age in the rate of protein synthesis resulting from a fall in capacity (RNA concentration) and activity (synthesis rate per unit of RNA). There was a fall with age in the breakdown rate so that the rate was highest in the weaning rats, with a half-life of 3 days. There was a direct correlation between the fractional growth and breakdown rates. During rehabilitation on the good diet, rapid growth was also accompanied by high rates of protein breakdown. During growth on the inadequate diet protein synthesis rates were lesss than in controls, but growth occurred because of decreased rates of protein breakdown. This compression was not complete, however, since ultimate muscle size was only one-half that of controls. It is suggested that increased rates of protein breakdown are a necessary accompaniment to muscle growth and may result from the way in which myofibrils proliferate.

scholarly journals Tumour necrosis factor (TNF) and interleukin-1 (IL-1) induce muscle proteolysis through different mechanisms

1992 ◽  
Vol 1 (4) ◽  
pp. 247-250 ◽  
Author(s):  
Oded Zamir ◽  
Per-Olof Hasselgren ◽  
Takashi Higashiguchi ◽  
Janice A. Frederick ◽  
Josef E. Fischer
Keyword(s):  
Glucocorticoid Receptor ◽  
Tumour Necrosis Factor ◽  
Tumour Necrosis ◽  
Extensor Digitorum Longus ◽  
Interleukin 1 ◽  
Myofibrillar Protein ◽  
Receptor Blocker ◽  
Protein Breakdown ◽  
Breakdown Rates ◽  
Necrosis Factor

The purpose of this study was to test the hypothesis that muscle proteolysis induced by TNF or IL-1 is mediated by glucocorticoids. Rats were treated with 300 μg kg−1of recombinant human preparations of IL-1α (rIL-1α) or TNFα (rTNFα) divided into three equal intraperitoneal doses given over 16 h. Two hours before each cytokine injection, rats were given 5 mg kg−1of the glucocorticoid receptor blocker mifepristone RU 38486, by gavage or were gavaged with the vehicle. Eighteen hours after the first cytokine injection, total and myofibrillar protein breakdown rates were determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Total and myofibrillar proteolytic rates were increased following injection of rIL-1α or rTNFα. Proteolysis induced by rIL-1α was not altered by treatment with RU 38486. In contrast, the glucocorticoid receptor blocker inhibited the proteolytic effect of rTNFα. The results suggest that the proteolytic effect of TNF is mediated by glucocorticoids and that IL-1 induces muscle proteolysis through a glucocorticoid independent pathway.

N τ-Methylhistidine Excretion and Myofibrillar Protein Breakdown in Patients Receiving Intravenous or Enteral Nutrition

1980 ◽  
Vol 59 (3) ◽  
pp. 211-214 ◽  
Author(s):  
I. B. Holbrook ◽  
E. Gross ◽  
P. J. Milewski ◽  
K. Shipley ◽  
M. H. Irving
Keyword(s):  
Enteral Nutrition ◽  
Muscle Protein ◽  
Myofibrillar Protein ◽  
Protein Breakdown ◽  
Breakdown Rate ◽  
Creatinine Excretion ◽  
Non Invasive ◽  
Breakdown Rates ◽  
Invasive Measurement

1. Nτ-Methylhistidine, nitrogen and creatinine were measured in the urine of 10 volunteers on normal and meat-free diets and in 10 vegetarians, and compared with the results from the urine of eight patients with intestinal fistulae on intravenous or enteral nutrition containing no meat. The values obtained were used to calculate fractional breakdown rate of myofibrillar protein. 2. There was a significant fall in the excretion of Nτ-methylhistidine and creatinine and in apparent fractional breakdown rates after 2 days on a meat-free diet. 3. One of the patients had lower, and two of the patients had higher, fractional breakdown rates compared with the vegetarians. 4. Nτ-Methylhistidine and creatinine excretion-5-be a useful and non-invasive measurement of myofibrillar protein degradation in patients on meat-free diets. Firm conclusions cannot, however, be drawn without confirmatory, direct measurement of the breakdown rates of muscle protein in vivo.

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.

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.

scholarly journals Prostaglandin E2 does not regulate total or myofibrillar protein breakdown in incubated skeletal muscle from normal or septic rats

1990 ◽  
Vol 270 (1) ◽  
pp. 45-50 ◽  
Author(s):  
P O Hasselgren ◽  
O Zamir ◽  
J H James ◽  
J E Fischer
Keyword(s):  
Skeletal Muscle ◽  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Plasma Levels ◽  
Muscle Protein ◽  
Myofibrillar Protein ◽  
Protein Breakdown ◽  
Muscle Protein Breakdown

The role of prostaglandins in the regulation of muscle protein breakdown is controversial. We examined the influence of arachidonic acid (5 microM), prostaglandin E2 (PGE2) (2.8 microM) and the prostaglandin-synthesis inhibitor indomethacin (3 microM) on total and myofibrillar protein breakdown in rat extensor digitorum longus and soleus muscles incubated under different conditions in vitro. In other experiments, the effects of indomethacin, administered in vivo to septic rats (3 mg/kg, injected subcutaneously twice after induction of sepsis by caecal ligation and puncture) on plasma levels and muscle release of PGE2 and on total and myofibrillar protein breakdown rates were determined. Total and myofibrillar proteolysis was assessed by measuring production by incubated muscles of tyrosine and 3-methylhistidine respectively. Arachidonic acid or PGE2 added during incubation of muscles from normal rats did not affect total or myofibrillar protein degradation under a variety of different conditions in vitro. Indomethacin inhibited muscle PGE2 production by incubated muscles from septic rats, but did not lower proteolytic rates. Administration in vivo of indomethacin did not affect total or myofibrillar muscle protein breakdown, despite effective plasma levels of indomethacin with decreased plasma PGE2 levels and inhibition of muscle PGE2 release. The present results suggest that protein breakdown in skeletal muscle of normal or septic rats is not regulated by PGE2 or other prostaglandins.

IGF-I stimulates protein synthesis but does not inhibit protein breakdown in muscle from septic rats

1998 ◽  
Vol 274 (2) ◽  
pp. R571-R576 ◽  
Author(s):  
Scott C. Hobler ◽  
Arthur B. Williams ◽  
Josef E. Fischer ◽  
Per-Olof Hasselgren
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cecal Ligation ◽  
Myofibrillar Protein ◽  
Maximal Effect ◽  
Protein Breakdown ◽  
Breakdown Rates ◽  
Igf I ◽  
Dose Dependent Fashion ◽  
High Concentrations

Sepsis is associated with reduced protein synthesis and increased protein degradation in skeletal muscle. We examined the effects of insulin-like growth factor I (IGF-I) on protein synthesis and breakdown in muscles from nonseptic and septic rats. Sepsis was induced by cecal ligation and puncture; control rats were sham operated. Extensor digitorum longus muscles were incubated in the absence or presence of IGF-I at concentrations ranging from 100 ng/ml to 10 μg/ml. Total and myofibrillar protein breakdown rates were measured as net release of tyrosine and 3-methylhistidine, respectively. Protein synthesis was determined by measuring incorporation of [U-14C]phenylalanine into protein. IGF-I stimulated protein synthesis in a dose-dependent fashion in muscles from both sham-operated and septic rats, with a maximal effect seen at a hormone concentration between 500 and 1,000 ng/ml. IGF-I inhibited total and myofibrillar protein breakdown in muscles from sham-operated rats, whereas in muscles from septic rats, IGF-I had no effect on protein breakdown, even at high concentrations. The results suggest that protein breakdown in skeletal muscle becomes resistant to IGF-I during sepsis and that this resistance reflects a postreceptor defect.

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)

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