Protein synthesis in skeletal muscle of the perfused rat hemicorpus compared with rates in the intact animal

The rate of protein synthesis was measured in muscles of the perfused rat hemicorpus, and values were compared with rates obtained in whole animals. In gastrocnemius muscle of fed rats the rate of synthesis measured in the hemicorpus was the same as that in the whole animal. However, in plantaris, quadriceps and soleus muscles rates were higher in the hemicorpus than those in vivo. In the hemicorpus, starvation for 1 day decreased the rate of protein synthesis in gastrocnemius and plantaris muscles, in parallel with decreases in the RNA content, but the soleus remained unaffected. Similar effects of starvation were observed in vivo, so that the relationships between rates in vivo and in the hemicorpus were the same as those in fed rats. Proteins of quadriceps and plantaris muscles were separated into sarcoplasmic and myofibrillar fractions. The rate of synthesis in the sarcoplasmic fraction of the hemicorpus from fed rats was similar to that in vivo, but synthesis in the myofibrillar fraction was greater. In the plantaris of starved rats the rates of synthesis in both fractions were lower, but the relationships between rates measured in vivo and in the perfused hemicorpus were similar to those seen in fed rats. The addition of insulin to the perfusate of the hemicorpus prepared from 1-day-starved animals increased the rates of protein synthesis per unit of RNA in gastrocnemius and plantaris muscles to values above those seen in fed animals when measured in vivo or in the hemicorpus. Insulin had no effect on the soleus. Overall, the rates of protein synthesis in the hemicorpus differed from those in vivo. However, the effect of starvation when measured in the whole animal was very similar to that measured in the isolated rat hemicorpus when insulin was omitted from the perfusate.

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Protein turnover in rat skeletal muscle: effects of hypophysectomy and growth hormone.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1978.234.1.e38 ◽

1978 ◽

Vol 234 (1) ◽

pp. E38 ◽

Cited By ~ 1

Author(s):

K E Flaim ◽

J B Li ◽

L S Jefferson

Keyword(s):

Skeletal Muscle ◽

Growth Hormone ◽

Protein Synthesis ◽

Protein Turnover ◽

Gastrocnemius Muscle ◽

Growth Hormone Treatment ◽

Hormone Replacement ◽

Hormone Treatment ◽

Rat Skeletal Muscle

The role of growth hormone in regulating protein turnover was examined in a perfused preparation of rat skeletal muscle. The perfused muscle maintained in vivo levels of ATP and creatine phosphate and exhibited constant rates of oxygen consumption and protein synthesis. Hypophysectomy reduced the rate of protein synthesis, the concentration of RNA, and the efficiency of protein synthesis in gastrocnemius muscle to 30, 46, and 66 percent of normal, respectively. In vivo treatment of hypophysectomized (hypox) rats with bovine growth hormone (250 microgram/day for 5 days) resulted in small increases in protein synthesis and RNA, whereas synthesis/RNA was returned to near normal. Elevation of ribosomal subunits in psoas muscle indicated an inhibition of peptide-chain initiation in hypox rats that was reversed by in vivo growth hormone treatment. Thus, hypox rats exhibited both a decreased capacity and a decreased efficiency of protein synthesis. Growth hormone replacement primarily increased efficiency of protein synthesis. The rate of protein degradation and the activity of cathepsin D in gastrocnemius muscle were decreased by hypophysectomy. Growth hormone treatment had no significant effect on degradation.

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REDD1 deletion prevents dexamethasone-induced skeletal muscle atrophy

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00234.2014 ◽

2014 ◽

Vol 307 (11) ◽

pp. E983-E993 ◽

Cited By ~ 49

Author(s):

Florian A. Britto ◽

Gwenaelle Begue ◽

Bernadette Rossano ◽

Aurélie Docquier ◽

Barbara Vernus ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Muscle Mass ◽

Tibialis Anterior ◽

Skeletal Muscle Mass ◽

Gastrocnemius Muscle ◽

Mtorc1 Signaling ◽

Inhibition Of Protein Synthesis ◽

Stress Dependent

REDD1 (regulated in development and DNA damage response 1) has been proposed to inhibit the mechanistic target of rapamycin complex 1 (mTORC1) during in vitro hypoxia. REDD1 expression is low under basal conditions but is highly increased in response to several catabolic stresses, like hypoxia and glucocorticoids. However, REDD1 function seems to be tissue and stress dependent, and its role in skeletal muscle in vivo has been poorly characterized. Here, we investigated the effect of REDD1 deletion on skeletal muscle mass, protein synthesis, proteolysis, and mTORC1 signaling pathway under basal conditions and after glucocorticoid administration. Whereas skeletal muscle mass and typology were unchanged between wild-type (WT) and REDD1-null mice, oral gavage with dexamethasone (DEX) for 7 days reduced tibialis anterior and gastrocnemius muscle weights as well as tibialis anterior fiber size only in WT. Similarly, REDD1 deletion prevented the inhibition of protein synthesis and mTORC1 activity (assessed by S6, 4E-BP1, and ULK1 phosphorylation) observed in gastrocnemius muscle of WT mice following single DEX administration for 5 h. However, our results suggest that REDD1-mediated inhibition of mTORC1 in skeletal muscle is not related to the modulation of the binding between TSC2 and 14-3-3. In contrast, our data highlight a new mechanism involved in mTORC1 inhibition linking REDD1, Akt, and PRAS40. Altogether, these results demonstrated in vivo that REDD1 is required for glucocorticoid-induced inhibition of protein synthesis via mTORC1 downregulation. Inhibition of REDD1 may thus be a strategy to limit muscle loss in glucocorticoid-mediated atrophy.

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Protein synthesis in liver, skeletal muscle, and brown adipose tissue of rats fed a protein-deficient diet

Bioscience Reports ◽

10.1007/bf01120702 ◽

1983 ◽

Vol 3 (6) ◽

pp. 569-575 ◽

Cited By ~ 9

Author(s):

P. W. Emery ◽

N. J. Rothwell ◽

M. J. Stock

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Adipose Tissue ◽

Brown Adipose Tissue ◽

Protein Content ◽

Deficient Diet ◽

Rna Content ◽

Brown Adipose ◽

Tissue Protein Synthesis

Feeding protein-deficient diets to rats is known to stimulate diet-induced thermogenesis and activate brown adipose tissue (BAT). The fact that BAT protein content, unlike that of other tissues, is unnaffected by protein deficiency prompted us to measure tissue protein synthesis in vivo in animals maintained on normal- (18.8%) and low- (7.6%) protein (LP) diets. Protein synthesis was depressed in the liver of the LP rats due to a fall in RNA activity, with no change in RNA content, and synthesis was also reduced in skeletal muscle from the LP group, but this was due to decreased RNA content with no change in RNA activity. Conversely, protein synthesis, RNA, DNA, and protein content of interscapular BAT were all unaltered in protein-restricted animals. These data indicate that, unlike liver, skeletal muscle, and whole carcass, BAT protein synthesis is not reduced in protein-restricted rats, and this may be related to activation of thermo-genesis in the tissue.

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FRACTIONAL PROTEIN SYNTHESIS RATES IN VIVO OF CONTRACTILE AND CYTOPLASMIC PROTEIN FRACTIONS OF SKELETAL MUSCLE IN THE SEPTIC RAT.

Shock ◽

10.1097/00024382-199911001-00169 ◽

1999 ◽

Vol 12 (Supplement) ◽

pp. 54-55

Author(s):

C. Ferguson ◽

J. Coakley ◽

M. Koll ◽

C. J. Hinds ◽

M. OʼLeary ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Protein Fractions ◽

Cytoplasmic Protein

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Effects of food deprivation on protein synthesis and degradation in rat skeletal muscles

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.2.441 ◽

1976 ◽

Vol 231 (2) ◽

pp. 441-448 ◽

Cited By ~ 173

Author(s):

JB Li ◽

AL Goldberg

Keyword(s):

Amino Acids ◽

Protein Synthesis ◽

Food Deprivation ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Rna Content ◽

Fasted Rats ◽

Synthesis And Degradation

The effects of food deprivation on protein turnover in rat soleus and extensor digitorum longus (EDL) were investigated. Muscles were removed from fed or fasted growing rats, and protein synthesis and breakdown were measured during incubation in vitro. Rates of synthesis and degradation were higher in the dark soleus than in the pale EDL. One day after food removal protein synthesis and RNA content in the EDL decreased. On the 2nd day of fasting, rates of protein catabolism in this muscle increased. Little or no change in synthesis and degradation occurred in the soleus. Consequently, during fasting the soleus lost much less weight than the EDL and other rat muscles. In unsupplemented buffer or in medium containing amino acids, glucose, and insulin, the muscles of fasted rats showed a lower rate of protein synthesis expressed per milligram of tissue but not per microgram of RNA. Thus the decrease in muscle RNA on fasting was responsible for the reduced synthesis observed under controlled in vitro conditions. In vivo the reduction in muscle protein synthesis on fasting results both from a lower RNA content and lower rate of synthesis per microgram of RNA. Reduced supply of glucose, insulin, and amino acids may account for the lower rate of synthesis per microgram of RNA demonstrable in vivo.

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Tissue spaces in rat heart, liver, and skeletal muscle in vivo

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1998.275.5.r1530 ◽

1998 ◽

Vol 275 (5) ◽

pp. R1530-R1536 ◽

Cited By ~ 21

Author(s):

Julie Cieslar ◽

Ming-Ta Huang ◽

Geoffrey P. Dobson

Keyword(s):

Skeletal Muscle ◽

Rat Heart ◽

Gastrocnemius Muscle ◽

Interstitial Space ◽

Glyceric Acid ◽

Sprague Dawley ◽

Tissue Water ◽

Intracellular Space ◽

Total Tissue

Tissue spaces were determined in rat heart, liver, and skeletal muscle in vivo using isotopically labeled [14C]inulin. Tracer was injected into the jugular vein of pentobarbital-anesthetized male Sprague-Dawley rats. After a 30-min equilibration period, a blood sample was taken, and heart, liver, and gastrocnemius muscle were excised and immediately freeze clamped at liquid nitrogen temperatures. The extracellular inulin space was 0.209 ± 0.006 ( n = 13), 0.203 ± 0.080 ( n = 7), and 0.124 ± 0.006 (SE) ml/g wet wt tissue ( n = 8) for heart, liver, and skeletal muscle, respectively. Total tissue water was 0.791 ± 0.005 ( n = 9), 0.732 ± 0.002 ( n = 9), and 0.755 ± 0.005 ml/g wet wt tissue ( n = 10) for heart, liver, and skeletal muscle, respectively. Expressed as a percentage of total tissue water, the intracellular space was 73.6, 72.2, and 83.7% for heart, liver, and skeletal muscle, respectively. With use of 2,3-diphospho-d-glyceric acid as a vascular marker, the interstitial space was calculated by subtracting the counts in tissue due to whole blood from total tissue counts and dividing by plasma counts. The interstitial space was 18.8, 22.4, and 14.5% of total tissue water, with accompanying plasma spaces of 7.7, 5.3, and 1.8% for heart, liver, and gastrocnemius muscle, respectively. The tracer method used in this study provides a quantitative assessment of water distribution in tissues of nonnephrectomized rats that has applications for calculation of tissue ion and metabolite concentrations, gradients, and fluxes under normal and pathophysiological conditions.

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Nitric Oxide Synthase Inhibitors do not Ameliorate Alcohol-Induced Reductions in Skeletal Muscle Protein Synthesis in Vivo

Clinical Science ◽

10.1042/cs099018pb ◽

2000 ◽

Vol 99 (s43) ◽

pp. 18P-18P

Author(s):

R Rajendram ◽

JS Marway ◽

TJ Peters ◽

VR Preedy

Keyword(s):

Nitric Oxide ◽

Skeletal Muscle ◽

Protein Synthesis ◽

Nitric Oxide Synthase ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Skeletal Muscle Protein ◽

Skeletal Muscle Protein Synthesis ◽

Oxide Synthase

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Albumin, fibrinogen and transferrin synthesis in isolated rat hepatocyte suspensions. A model for the study of plasma protein synthesis

Biochemical Journal ◽

10.1042/bj1460141 ◽

1975 ◽

Vol 146 (1) ◽

pp. 141-155 ◽

Cited By ~ 150

Author(s):

K N Jeejeebhoy ◽

J Ho ◽

G R Greenberg ◽

M J Phillips ◽

A Bruce-Robertson ◽

...

Keyword(s):

Amino Acids ◽

Growth Hormone ◽

Protein Synthesis ◽

Plasma Protein ◽

Plasma Proteins ◽

Horse Serum ◽

Rat Hepatocyte ◽

Isolated Rat

A system using hepatocyte suspensions in vitro was developed for studying the synthesis of albumin, fibrinogen and transferrin. Conditions for optimum survival of the hepatocyte and for synthesis of these plasma proteins were defined for this system. These conditions included the use of horse serum (17.5 percent, v/v, heat-inactivated), an enriched medium (Waymouth's MB 752/1), an O2 tension of between 18.7 times 10(3) and 26.7 times 10(3) Pa and constant stirring. Albumin, fibrinogen and transferrin synthesis rates were obtained of 0.32 p 0.094(10), 0.12 p 0.030(11) and 0.097 p 0.017(10) [mean p S.D. (n)]mg/h per g of hepatocytes respectively. These rates were maintained for the first 12h of study and synthesis continued at a diminished rate up to 48h. The synthesis of albumin was decreased in a medium containing less amino acids and glucose, but that of fibrinogen was substantially unaffected. ATP concentrations up to 12h and RNA/DNA ratios up to 24h were comparable with values in vivo. The ability to study cells up to 48h permitted us to find that the addition of a mixture of hormones consisting of glucagon, cortisol, tri-iodothyronine and growth hormone enhanced fibrinogen synthesis. Addition of insulin to the above mixture resulted in increased synthesis for albumin and transferrin but not for fibrinogen.

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Effects of potassium deficiency on growth and protein synthesis in skeletal muscle and the heart of rats

British Journal Of Nutrition ◽

10.1079/bjn19890029 ◽

1989 ◽

Vol 62 (2) ◽

pp. 269-284 ◽

Cited By ~ 23

Author(s):

Inge Dôrup ◽

Torben Clausen

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Muscle Protein ◽

Control Level ◽

Inhibitory Effect ◽

Potassium Deficiency ◽

Skeletal Muscle Protein ◽

K Deficiency

The effects of potassium deficiency on growth, K content and protein synthesis have been compared in 4–13-week-old rats. When maintained on K-deficient fodder (1 mmol/kg) rats ceased to grow within a few days, and the incorporation of [3H]leucine into skeletal muscle protein in vivo was reduced by 28–38%. Pair-feeding experiments showed that this inhibition was not due to reduced energy intake. Following 14 d on K-deficient fodder, there was a further reduction (39–56 %) in the incorporation of [3H]leucine into skeletal muscle protein, whereas the incorporation into plasma, heart and liver proteins was not affected. The accumulation of the non-metabolized amino acid α-aminoisobutyric acid in the heart and skeletal muscles was not reduced. The inhibitory effect of K deficiency on 3H-labelling of muscle protein was seen following intraperitoneal (10–240 min) as well as intravenous (10 min) injection of [3H]leucine. In addition, the incorporation of [3H]phenylalanine into skeletal muscle protein was reduced in K-depleted animals. Following acute K repletion in vivo leading to complete normalization of muscle K content, the incorporation of [3H]leucine into muscle protein showed no increase within 2 h, but reached 76 and 104% of the control level within 24 and 72 h respectively. This was associated with a rapid initial weight gain, but normal body-weight was not reached until after 7 weeks of K repletion. Following 7 d on K-deficient fodder the inhibition of growth and protein synthesis was closely correlated with the K content of the fodder (1–40 mmol/kg) and significant already at modest reductions in muscle K content. In vitro experiments with soleus muscle showed a linear relationship between the incorporation of [3H]leucine into muscle protein and K content, but the sensitivity to cellular K deficiency induced in vitro was much less pronounced than that induced in vivo. Thus, in soleus and extensor digitorum longus (EDL) muscles prepared from K-deficient rats, the incorporation of [3H]leucine was reduced by 30 and 47 % respectively. This defect was completely restored by 24 h K repletion in vivo. It is concluded that in the intact organism protein synthesis and growth are very sensitive to dietary K deficiency and that this can only partly be accounted for by the reduction in cellular K content per se. The observations emphasize the need for adequate K supplies to ensure optimum utilization of food elements for protein synthesis and growth.

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