scholarly journals The effects of denervation on protein turnover of rat skeletal muscle

1976 ◽  
Vol 156 (1) ◽  
pp. 71-80 ◽  
Author(s):  
D F Goldspink
Keyword(s):  
Protein Synthesis ◽  
Conformational Changes ◽  
Extensor Digitorum Longus ◽  
Soluble Proteins ◽  
Extensor Digitorum ◽  
Muscle Weight ◽  
Active Involvement ◽  
Two Phases ◽  
Denervated Muscles

The effects of denervation on muscle weight, rates of protein synthesis and breakdown, and RNA concentraitons were studied in the soleus and extensor digitorum longus muscle. Althrough the soleus underwent a true atrophy after section of the sciatic nerve, the extensor digitorum longus continued to grow, albeit at a lower rate than innervated controls. At 24h after nerve section protein breakdown was increased in both muscle types when compared with internal controls, and remained so throughout the 10 days studied. The possibility that this increased catabolism might arise from conformational changes of proteins after denervation was not substantiated, as myofibrillar or soluble proteins of denervated and control tissues were equally susceptible to degradation in vitro by three proteinases. Tyrosine uptake into the denervated extensor digitorum longus was decreased throughout the 10 days studied, whereas two phases of increased transport of the amino acid were found in the soleus. Significant decreases in rates of protein synthesis were found 1 and 2 days after denervation and results are presented that suggest that these changes may result from a decrease in ribosomal involvement in the translation process. These initial decreases were not maintained and the rate of protein synthesis was in fact increased when compared with controls, at 7 and 10 days. The increased synthetic rates of the 7-day denervated tissues were reflected as proportional increases in both myofibrillar and soluble proteins. It is suggested that the increase in synthesis at this time may result from an increase in both the abailability and active involvement of ribosomes, and that these anabolic trends may be caused by spontaneous fibrillation and/or the amount of passive stretching of the denervated muscles.

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 The influence of passive stretch on the growth and protein turnover of the denervated extensor digitorum longus muscle

1978 ◽  
Vol 174 (2) ◽  
pp. 595-602 ◽  
Author(s):  
David F. Goldspink
Keyword(s):  
Protein Synthesis ◽  
Extensor Digitorum Longus ◽  
Similar Rate ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Denervated Muscle ◽  
Longus Muscle ◽  
Induced Changes ◽  
Passive Stretch

At 7 days after cutting the sciatic nerve, the extensor digitorum longus muscle was smaller and contained less protein than its innervated control. Correlating with these changes was the finding of elevated rates of protein degradation (measured in vitro) in the denervated tissue. However, at this time, rates of protein synthesis (measured in vitro) and nucleic acid concentrations were also higher in the denervated tissue, changes more usually associated with an active muscle rather than a disused one. These anabolic trends have, at least in part, been explained by the possible greater exposure of the denervated extensor digitorum longus to passive stretch. When immobilized under a maintained influence of stretch the denervated muscle grew to a greater extent. Although this stretch-induced growth appeared to occur predominantly through a stimulation of protein synthesis, it was opposed by smaller increases in degradative rates. Nucleic acids increased at a similar rate to the increase in muscle mass when a continuous influence of stretch was imposed on the denervated tissue. In contrast, immobilization of the denervated extensor digitorum longus in a shortened unstretched state reversed most of the stretch-induced changes; that is, the muscle became even smaller, with protein synthesis decreasing to a greater extent than breakdown after the removal of passive stretch. The present investigation suggests that stretch will promote protein synthesis and hence growth of the extensor digitorum longus even in the absence of an intact nerve supply. However, some factor(s), in addition to passive stretch, must contribute to the anabolic trends in this denervated muscle.

scholarly journals The effects of cutting or of stretching skeletal muscle in vitro on the rates of protein synthesis and degradation

1980 ◽  
Vol 188 (1) ◽  
pp. 247-254 ◽  
Author(s):  
M J Seider ◽  
R Kapp ◽  
C P Chen ◽  
F W Booth
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Extensor Digitorum Longus ◽  
High Energy ◽  
Extensor Digitorum ◽  
Muscle Fibres ◽  
High Energy Phosphates ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Rates of protein synthesis were significantly lower in the cut soleus and extensor digitorum longus muscles than in their uncut counterparts. Rates of protein degradation were significantly higher in cut soleus muscles, but not in cut extensor digitorum longus muscles as compared with their uncut controls. Concentrations of ATP and phosphocreatine were significantly lower in cut soleus and extensor digitorum longus muscles after incubation in vitro in contrast with respective control uncut muscles. These data indicate that cutting of muscle fibres alters rates of protein synthesis and degradation, in addition to altering concentrations of high-energy phosphates. Since these findings stressed the importance of using intact muscles to study protein metabolism, additional studies were made on intact muscles in vitro. Stretched soleus muscles had higher concentrations of high-energy phosphates at the end of an incubation period than did unstretched muscles. However, the length of the soleus, extensor digitorum longus and diaphragm muscles during incubation did not affect rates of protein degradation.

scholarly journals Morphological observations and rates of protein synthesis in rat muscles incubated in vitro

1985 ◽  
Vol 232 (3) ◽  
pp. 927-930 ◽  
Author(s):  
C A Maltin ◽  
C I Harris
Keyword(s):  
Protein Synthesis ◽  
Extensor Digitorum Longus ◽  
Marked Decrease ◽  
Extensor Digitorum ◽  
Central Core ◽  
Phosphorylase Activity ◽  
Glucan Phosphorylase ◽  
Isolated Rat

Isolated soleus and extensor digitorum longus muscles from small (40 or 70 g) rats developed a central and substantial (13-57%) loss of glycogen and alpha-glucan phosphorylase activity after incubation for up to 2 h in vitro. The central ‘core’ of the muscles showed a marked decrease in the rate of protein synthesis. It is suggested that during brief periods of incubation the central core of isolated rat muscles becomes hypoxic, and that consequently the viability of such muscles must be in question.

scholarly journals Regulation of protein metabolism by a physiological concentration of insulin in mouse soleus and extensor digitorum longus muscles. Effects of starvation and scald injury

1979 ◽  
Vol 184 (2) ◽  
pp. 323-330 ◽  
Author(s):  
K N Frayn ◽  
P F Maycock
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Extensor Digitorum Longus ◽  
Muscle Protein ◽  
Extensor Digitorum ◽  
Total Protein Content ◽  
Skin Thickness ◽  
Physiological Concentration ◽  
Scald Injury

1. Although high concentrations of insulin affect both synthesis and degradation of skeletal-muscle protein, it is not known to what extent these effects occur with physiological concentrations. The effects of a physiological concentration of insulin (100 mu units/ml) on muscle protein synthesis, measured with [3H]tyrosine, and on muscle protein degradation, measured by tyrosine release in the presence of cycloheximide, were studied in mouse soleus and extensor digitorum longus muscles in vitro. 2. Insulin significantly stimualated protein synthesis in both muscles, but an inhibition of degradation was seen only in the extensor digitorum longus. 3. Starvation for 24 h decreased the rate of protein synthesis and increased the rate of breakdown in the extensor digitorum longus. Sensitivity to insulin-stimulation of proteins synthesis in the soleus was increased by starvation. 4.;a 20%-surface-area full-skin-thickness dorsal scald injury produced a fall in total protein content in soleus and extensor digitorum muscles, maximal on the third day after injury. Soleus muscles 2 days after injury showed an impairment of protein synthesis; degradation was unaffected and neither synthesis nor degradation in vitro was significantly affected in the extensor digitorum longus. 5. The advantages and limitations of studies of protein metabolism in vitro are discussed.

scholarly journals The action of the β-agonist clenbuterol on protein metabolism in innervated and denervated phasic muscles

1989 ◽  
Vol 261 (3) ◽  
pp. 965-971 ◽  
Author(s):  
C A Maltin ◽  
S M Hay ◽  
M I Delday ◽  
G E Lobley ◽  
P J Reeds
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Temporal Response ◽  
Muscle Type ◽  
Fractional Rate ◽  
Denervated Muscles ◽  
Gastrocnemius Muscles

1. Clenbuterol treatment in innervated and denervated phasic extensor digitorum longus, plantaris and gastrocnemius muscles from rats caused a significant increase in RNA and protein contents in all muscles except denervated extensor digitorum longus. 2. All muscles showed an increase in the fractional rate of protein synthesis (Ks) with clenbuterol, but the temporal response varied. 3. The data suggest that the effect of clenbuterol on protein metabolism in innervated muscles is muscle-type specific, and demonstrate the homology of response for denervated muscles.

Correlation between magnesium and potassium contents in muscle: role of Na(+)-K+ pump

1993 ◽  
Vol 264 (2) ◽  
pp. C457-C463 ◽  
Author(s):  
I. Dorup ◽  
T. Clausen
Keyword(s):  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Deficient Diet ◽  
Young Rats ◽  
Wide Range ◽  
86Rb Influx

In young rats fed a Mg(2+)-deficient diet for 3 wk, Mg2+ and K+ contents in soleus and extensor digitorum longus muscles were significantly reduced and closely correlated. In isolated soleus muscles, Mg2+ depletion induced an even more pronounced loss of K+, and Mg2+ and K+ contents were correlated over a wide range (r = 0.95, P < 0.001). Extracellular Mg2+ (0-1.2 mM) caused no change in total or ouabain-suppressible 86Rb influx. After long-term incubation in Ca(2+)-Mg(2+)-free buffer with EDTA and EGTA, cellular Mg2+ and K+ contents were reduced by 35 and 15%, respectively, without any reduction in ATP and total or ouabain-suppressible 86Rb influx. In Mg(2+)-depleted muscles 42K efflux was increased by up to 42%, and repletion with Mg2+ produced a graded decrease. We conclude that Mg2+ and K+ contents are closely correlated in muscles Mg2+ depleted in vivo or in vitro and that neither extracellular nor moderate intracellular Mg2+ depletion affects total or Na(+)-K+ pump-mediated K+ influx. The reduced K+ content may rather be related to increased K+ efflux from the muscles.

Phospholipids, prostaglandin E2, and proteolysis in denervated muscle

1986 ◽  
Vol 251 (1) ◽  
pp. R165-R173 ◽  
Author(s):  
J. Turinsky
Keyword(s):  
Protein Synthesis ◽  
Prostaglandin E2 ◽  
Pge2 Production ◽  
Nerve Transection ◽  
Denervated Muscle ◽  
Sciatic Nerve Transection ◽  
Tissue Protein ◽  
Pge2 Release ◽  
Denervated Muscles

Soleus muscles of rats were studied up to 16 days after sciatic nerve transection. At the end of this period the denervated soleus muscles exhibited decreased content of diphosphatidylglycerol (-44%), normal level of phosphatidylethanolamine, and increased contents of phosphatidylcholine (+24%), sphingomyelin (+48%), lysophosphatidylcholine (+110%), phosphatidylinositol (+37%), and phosphatidylserine (+40%) per milligram of tissue protein. In studies in vitro, prostaglandin E2 (PGE2) release and tyrosine release by denervated soleus muscles were 319 and 141%, respectively, greater than those of sham muscles. An almost complete inhibition of PGE2 release with 5 X 10(-4) M aspirin or 2.8 X 10(-6) M indomethacin had no effect on tyrosine release of sham muscles or the stimulated tyrosine release of the denervated muscles. Addition of 5 X 10(-5) M cycloheximide in the medium resulted in 63% inhibition of PGE2 release by both groups of muscles; concomitant absolute increments in tyrosine releases by denervated and sham muscles did not statistically differ. In the presence of both 5 X 10(-5) M cycloheximide and 5 X 10(-4) M aspirin in the medium, PGE2 production by denervated and sham muscles was inhibited 87% while tyrosine release of denervated muscles was 108% higher than that of sham animals. It is concluded that 1) atrophy of denervated soleus muscle is associated with stimulated activity of tissue phospholipase A2, increased production of prostaglandin E2, increased total proteolytic rate, and unchanged rate of protein synthesis; 2) acute inhibition of PGE2 production does not inhibit the stimulated proteolysis in denervated muscle; and 3) cycloheximide inhibits PGE2 production by muscle.

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