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 Relationship between intracellular amino acids and protein synthesis in the extensor digitorum longus muscle of rats

1969 ◽  
Vol 114 (2) ◽  
pp. 171-178 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Free Amino ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Intracellular Amino Acids ◽  
Free Amino Acid Pools

1. The incorporation into protein, and the accumulation into the free amino acid pools, of radioactive l-leucine and glycine was studied in rat extensor digitorum longus muscle. 2. The tissue was incubated first with 14C-labelled and then with 3H-labelled amino acid. 3. The experimental results were consistent with a model based on the premise that the amino acids in protein were incorporated directly from the extracellular pool.

scholarly journals The influence of electrical stimulation in vitro on protein synthesis and other metabolic parameters of rat extensor digitorum longus muscle

1970 ◽  
Vol 118 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Virginia M. Pain ◽  
K. L. Manchester
Keyword(s):  
Amino Acids ◽  
Electrical Stimulation ◽  
Amino Acid ◽  
Extensor Digitorum Longus ◽  
Glucose Consumption ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Longus Muscle

1. Apparatus is described in which rat extensor digitorum longus muscle can be incubated in buffer under conditions of light tension and be subject to contractures induced by electrical stimulation in vitro. Under these conditions the tissue retains its weight, its content of potassium and size of the extracellular space at values similar to those in vivo. 2. Though uptake of glucose was enhanced on addition of insulin, there was little increase in glucose consumption on stimulation. Breakdown of glycogen and enhancement of lactate output were found on stimulation. 3. Incorporation into protein of several labelled amino acids was diminished during stimulation. Accumulation of [14C]leucine was enhanced whereas that of glycine was decreased. 4. There were no very consistent changes in the content of free unlabelled amino acids during incubation with or without stimulation. Comparison of actual amino acid concentrations in tissue and incubation mixture with accumulation of 14C-labelled amino acid indicated that full equilibration of the cell pool of amino amino acids with the medium is slow. 5. Substantial oxidation of several 14C-labelled acids was observed. 6. The ATP content of the tissue declined a little during incubation and somewhat faster after a period of stimulation. 7. The results are discussed in relation to the way in which exercise can induce muscle hypertrophy.

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.

Insulin sensitivity of rat skeletal muscle: effects of starvation and aging.

1979 ◽  
Vol 236 (5) ◽  
pp. E519 ◽  
Author(s):  
M N Goodman ◽  
N B Ruderman
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Extensor Digitorum Longus ◽  
Glucose Utilization ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Low Concentrations ◽  
Longus Muscle ◽  
Relative Differences

The effects of starvation and of aging on the sensitivity of skeletal muscle to insulin were studied in the isolated perfused rat hindquarter preparation. As we have shown previously, starvation for 48 h had no effect on glucose uptake in hindquarters perfused with high levels of insulin (5 and 20 mU/ml). On the other hand, in the presence of physiological concentrations of insulin (50--200 muU/ml), glucose utilization was substantially greater in starved rats. Low concentrations of insulin had a greater effect on glucose uptake in fed young (100-g) than in fed older (350-g) rats. Starvation for 48 h enhanced glucose uptake in both young and older rats; however, the relative differences persisted. Starvation had similar effects on glucose utilization by the incubated soleus and extensor digitorum longus muscle. In addition, it augmented the stimulation by insulin of alpha-aminoisobutyric acid transport into the incubated extensor digitorum longus muscle. These results suggest that the in vitro sensitivity of skeletal muscle to physiological concentrations of insulin is enhanced during starvation. The basis for these findings and their physiological implications remain to be determined.

scholarly journals 146 Prematurity Blunts the Protein Synthetic Response of Skeletal Muscle to Insulin and Amino Acids

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 118-119
Author(s):  
Teresa A Davis ◽  
Marko Rudar ◽  
Jane Naberhuis ◽  
Agus Suryawan ◽  
Marta Fiorotto
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Body Weight Gain ◽  
Human Infant ◽  
Long Term Effects ◽  
Plasma Insulin Concentration ◽  
Akt Phosphorylation ◽  
Relative Body Weight

Abstract Livestock animals are important dual-purpose models that benefit both agricultural and biomedical research. The neonatal pig is an appropriate model for the human infant to assess long-term effects of early life nutrition on growth and metabolic outcomes. Previously we have demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. The objective of this study was to determine whether reduced sensitivity to insulin and/or amino acids drives this blunted response. Pigs were delivered by caesarean section at preterm (PT, 103 d gestation) or at term (T, 112 d gestation) and fed parenterally for 4 d. On day 4, pigs were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps for 120 min, yielding six treatments: PT-FAST (n = 7), PT-INS (n = 9), PT-AA (n = 9), T-FAST (n = 8), T-INS (n = 9), and T-AA (n = 9). A flooding dose of L-[4-3H]Phe was injected into pigs 30 min before euthanasia. Birth weight and relative body weight gain were lower in PT than T pigs (P < 0.001). Plasma insulin concentration was increased from ~3 to ~100 µU/mL in INS compared to FAST and AA pigs (P < 0.001); plasma BCAA concentration was increased from ~250 to ~1,000 µmol/L in AA compared to FAST and INS pigs (P < 0.001). Despite achieving similar insulin and amino acid levels, longissimus dorsi AKT phosphorylation, mechanistic target of rapamycin (mTOR)·Rheb abundance, mTOR activation, and protein synthesis were lower in PT-INS than T-INS pigs (Table 1). Although amino-acid induced dissociation of Sestrin2 from GATOR2 was not affected by prematurity, mTOR·RagA abundance, mTOR·RagC abundance, mTOR activation, and protein synthesis were lower in PT-AA than T-AA pigs. The impaired capacity of premature skeletal muscle to respond to insulin or amino acids and promote protein synthesis likely contributes to reduced lean mass accretion. Research was supported by NIH and USDA.

Effect of Cycloheximide on In Vitro and In Vivo Protein Synthesis by Certain Tissues of Rats and Pigeons with Special Reference to Muscle

1973 ◽  
Vol 51 (12) ◽  
pp. 933-941 ◽  
Author(s):  
Njanoor Narayanan ◽  
Jacob Eapen
Keyword(s):  
Amino Acids ◽  
Body Weight ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Incorporation ◽  
Contrast Administration ◽  
Acid Incorporation ◽  
Tissue Homogenates

The effect of cycloheximide in vitro and in vivo on the incorporation of labelled amino acids into protein by muscles, liver, kidneys, and brain of rats and pigeons was studied. In vitro incorporation of amino acids into protein by muscle microsomes, myofibrils, and myofibrillar ribosomes was not affected by cycloheximide. In contrast, administration of the antibiotic into intact animals at a concentration of 1 mg/kg body weight resulted in considerable inhibition of amino acid incorporation into protein by muscles, liver, kidneys, and brain. This inhibition was observed in all the subcellular fractions of these tissues during a period of 10–40 min after the administration of the precursor. Tissue homogenates derived from in vivo cycloheximide-treated animals did not show significant alteration in in vitro amino acid incorporation with the exception of brain, which showed a small but significant enhancement.

scholarly journals Action of growth hormone in vitro on the net uptake and incorporation into protein of amino acids in muscle from intact rabbits given protein-deficient diets

1976 ◽  
Vol 35 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. R. Turner ◽  
P. J. Reeds ◽  
K. A. Munday
Keyword(s):  
Amino Acids ◽  
Growth Hormone ◽  
Protein Synthesis ◽  
Amino Acid ◽  
De Novo ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Amino Acid Incorporation ◽  
Acid Incorporation

1. Net amino acid uptake, and incorporation into protein have been measured in vitro in the presence and absence of porcine growth hormone (GH) in muscle from intact rabbits fed for 5 d on low-protein (LP), protein-free (PF) or control diets.2. In muscle from control and LP animals GH had no effect on the net amino acid uptake but stimulated amino acid incorporation into protein, although this response was less in LP animals than in control animals.3. In muscle from PF animals, GH stimulated both amino acid incorporation into protein and the net amino acid uptake, a type of response which also occurs in hypophysectomized animals. The magnitude of the effect of GH on the incorporation of amino acids into protein was reduced in muscle from PF animals.4. The effect of GH on the net amino acid uptake in PF animals was completely blocked by cycloheximide; the uptake effect of GH in these animals was dependent therefore on de novo protein synthesis.5. It is proposed that in the adult the role of growth hormone in protein metabolism is to sustain cellular protein synthesis when there is a decrease in the level of substrate amino acids, similar to that which occurs during a short-term fast or when the dietary protein intake is inadequate.

scholarly journals Action of insulin and growth hormone on protein synthesis in muscle from non-hypophysectomized rabbits

1971 ◽  
Vol 125 (2) ◽  
pp. 515-520 ◽  
Author(s):  
P. J. Reeds ◽  
K. A. Munday ◽  
M. R. Turner
Keyword(s):  
Amino Acids ◽  
Growth Hormone ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Amino Acid Uptake ◽  
Diaphragm Muscle ◽  
Acid Uptake

The separate effects of insulin and growth hormone on the uptake and incorporation of five amino acids into diaphragm muscle from non-hypophysectomized rabbits has been examined. Both growth hormone and insulin, when present in the medium separately, stimulated the incorporation into protein of the amino acids, leucine, arginine, valine, lysine and histidine. Insulin also stimulated amino acid uptake, but growth hormone did not. When insulin and growth hormone were present in the incubation medium together, the uptake and incorporation of valine, the only amino acid studied under these conditions, tended to be greater than the sum of the separate effects of the two hormones.

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