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PubMed1998

Response of skeletal muscle protein synthesis to insulin in suckling pigs decreases with development.

The elevated rate of muscle protein deposition in the neonate is largely due to an enhanced stimulation of skeletal muscle protein synthesis by feeding. To examine the role of insulin in this response, hyperinsulinemic-euglycemic-amino acid clamps were performed in 7- and 26-day-old pigs. Pigs were infused with 0, 30, 100, or 1,000 ng . kg-0.66 . min-1 of insulin to mimic the plasma insulin levels observed under fasted, fed, refed, and supraphysiological conditions, respectively. Whole body amino acid disposal was determined from the rate of infusion of an amino acid mixture necessary to maintain plasma essential amino acid concentrations near their basal fasting levels. A flooding dose of L-[4-3H]phenylalanine was used to measure skeletal muscle protein synthesis. Whole body amino acid disposal increased progressively as the insulin infusion rate increased, and this response was greater in 7- than in 26-day-old pigs. Skeletal muscle protein synthesis was stimulated by insulin, and this response was maximal at a low insulin infusion rate (30 ng . kg-0.66 . min-1). The stimulation of muscle protein synthesis by insulin was also greater in 7- than in 26- day-old pigs. These data suggest that muscle protein synthesis is more sensitive to insulin than whole body amino acid disposal. The results further suggest that insulin is a central regulatory factor in the elevated rate of muscle protein deposition and the increased response of skeletal muscle protein synthesis to feeding in the neonate.

Amino Acids↗

PubMed2002

Resistance-training-induced adaptations in skeletal muscle protein turnover in the fed state.

Resistance training changes the balance of muscle protein turnover, leading to gains in muscle mass. A longitudinal design was employed to assess the effect that resistance training had on muscle protein turnover in the fed state. A secondary goal was investigation of the potential interactive effects of creatine (Cr) monohydrate supplementation on resistance-training-induced adaptations. Young (N = 19, 23.7 +/- 3.2 year), untrained (UT), healthy male subjects completed an 8-week resistance-training program (6 d/week). Supplementation with Cr had no impact on any of the variables studied; hence, all subsequent data were pooled. In the UT and trained (T) state, subjects performed an acute bout of resistance exercise with a single leg (exercised, EX), while their contralateral leg acted as a nonexercised (NE) control. Following exercise, subjects were fed while receiving a primed constant infusion of [d5]- and [15N]-phenylalanine to determine the fractional synthetic and breakdown rates (FSR and FBR), respectively, of skeletal muscle proteins. Acute exercise increased FSR (UT-NE, 0.065 +/- 0.025 %/h; UT-EX, 0.088 +/- 0.032 %/h; P < 0.01) and FBR (UT-NE, 0.047 +/- 0.023 %/h; UT-EX, 0.058 +/- 0.026 %/h; P < 0.05). Net balance (BAL = FSR - FBR) was positive in both legs (P < 0.05) but was significantly greater (+65%) in the EX versus the NE leg (P < 0.05). Muscle protein FSR and FBR were greater at rest following T (FSR for T-NE vs. UT-NE, +46%, P < 0.01; FBR for T-NE vs. UT-NE, +81%, P < 0.05). Resistance training attenuated the acute exercise-induced rise in FSR (T-NE vs. T-EX, +20%, P = 0.65). The present results demonstrate that resistance training resulted in an elevated resting muscle protein turnover but an attenuation of the acute response of muscle protein turnover to a single bout of resistance exercise.

Adult↗

PubMed2004

Impaired anabolic response of muscle protein synthesis is associated with S6K1 dysregulation in elderly humans.

Age-related loss of muscle protein may involve a decreased response to anabolic factors of muscle protein synthesis through dysregulation of translation factors. To verify this hypothesis, we simultaneously investigated muscle protein synthesis and expression of some factors implicated in insulin signal transduction during hyperinsulinemia and hyperaminoacidemia in 6 young (25+/-1 year; mean+/-sem) and 8 elderly subjects (72+/-2 year). Incorporation of L-[1-13C] leucine in muscle proteins (fractional synthesis rate, FSR) was measured in vastus lateralis, before and during a euglycemic hyperinsulinemic hyperaminoacidemic clamp, together with Western blot analysis of protein kinase B (PKB), mTOR, 4E-BP1, and S6K1 phosphorylation. In basal state, muscle protein FSR was reduced in elderly in comparison with young subjects (0.061+/-0.004% per hour) vs 0.082+/-0.010% per hour, elderly vs. young, P<0.05). During clamp, muscle protein FSR was stimulated in young (0.119+/-0.006% per hour; P<0.05), but this response was significantly lower in elderly subjects (0.084+/-0.005% per hour, P<0.05 vs young subjects). Phosphorylation of PKB, mTOR, and 4E-BP1 were similarly increased by insulin and amino acid in both groups, except for S6K1 phosphorylation, which was not stimulated in elderly subjects. In conclusion, 1) response of muscle protein synthesis to insulin and amino acid is impaired in elderly humans; 2) a defect in S6K1 pathway activation may be responsible for this alteration. This modification is a mechanistic basis of sarcopenia development during aging.

Adult↗

PubMed2000

The utility of resistance exercise training and amino acid supplementation for reversing age-associated decrements in muscle protein mass and function.

Advancing age is associated with reduced skeletal muscle protein synthesis, altered expression of and chemical modifications to muscle proteins, reduced muscle strength, muscle strength per unit muscle mass and muscle power (sarcopenia). These age-associated impairments in the quantity and quality of contractile protein contribute to physical disability and frailty, a loss of independent function, the risk of falling and fractures, and escalating health-care costs. Progressive resistance exercise training is a potent, non-pharmacologic, efficacious therapy for the impairment in muscle quantity and quality in middle age and physically frail adults. Evidence is accumulating that dietary amino acid supplementation may also improve muscle protein balance in the elderly. Several potential cellular mechanisms for the loss of muscle protein and resistance exercise-induced improvements in muscle quantity and quality in elderly adults are reviewed.

Aged↗

PubMed1973

Dietary protein intake and skeletal-muscle protein metabolism in rats. Studies with the ammonium chloride-wash fraction from crude polyribosomes of well-nourished and protein-depleted rats.

1. Crude polyribosomes from skeletal muscle of the hind leg of rats fed on a low-protein diet for 10 days are less active in cell-free protein synthesis than are polyribosomes obtained from well-nourished control rats. 2. The polyribosomes were salt-washed (0.5m-NH(4)Cl) and the wash extract was examined for its amino acid incorporating activity and for EF (elongation factor) 1 and EF 2 activities. 3. Compared with preparations from control rats, the salt-wash fraction from protein-depleted rats was less active and showed lower EF 1 and EF 2 activity. 4. The ribosomes were rendered equal in activity by salt-washing, but no inhibitor was detected in the salt wash. 5. Differences in the incorporating activity of crude polyribosomes from the diet groups persisted in the presence of saturating amounts of partially purified EF 1 and EF 2. 6. It is concluded that the lowered protein-synthetic activity of crude polyribosomes caused by restricted protein intake is not causally related to the lower activities of EF 1 and EF 2 in the polyribosome preparations. 7. The possible nature of the change in crude polyribosome activity due to low-protein feeding is discussed.

Amino Acids↗

PubMed2006

Modulation of muscle protein synthesis by insulin is maintained during neonatal endotoxemia.

Sepsis promotes insulin resistance and reduces protein synthesis in skeletal muscle of adults. The effect of sepsis on insulin-stimulated muscle protein synthesis has not been determined in neonates, a highly anabolic population that is uniquely sensitive to insulin. Overnight fasted neonatal pigs were infused for 8 h with endotoxin [lipopolysaccharide (LPS), 0 and 10 mug.kg(-1).h(-1)]. Glucose and amino acids were maintained at fasting levels, insulin was clamped at either fasting or fed (2 or 10 muU/ml) levels, and fractional protein synthesis rates were determined at the end of the infusion. LPS infusion induced a septic-like state, as indicated by a sustained elevation in body temperature, heart rate, and cortisol. At fasting insulin levels, LPS reduced fractional protein synthesis rates in gastrocnemius muscle (-26%) but had no effect on the masseter and heart. By contrast, LPS stimulated liver protein synthesis (+28%). Increasing insulin to fed levels accelerated protein synthesis rates in gastrocnemius (controls by +38%, LPS by +60%), masseter (controls by +50%, LPS by +43%), heart (controls by +34%, LPS by +40%), and diaphragm (controls by +54%, LPS by +29%), and the response to insulin was similar in LPS and controls. Insulin did not alter protein synthesis in liver, kidney, or jejunum in either group. These findings suggest that acute endotoxemia lowers basal fasting muscle protein synthesis in neonates but does not alter the response of protein synthesis to insulin.

Amino Acids, Branched-Chain↗

PubMed1995

Muscle protein turnover: methodological issues and the effect of aging.

Investigation of sarcopenia should include the measurement of muscle protein synthesis and breakdown because reduced muscle mass occurs only when muscle protein content is reduced. Protein content of a tissue is determined by the balance between synthesis and breakdown. Whole body measurements are inappropriate for determining the small changes in muscle protein synthesis and breakdown, since muscle contributes less than 30 percent to the whole body protein turnover. The measurement of mixed muscle protein synthesis in humans supports the animal data, which demonstrates that there is a decline in muscle protein synthesis with age. Resistance exercise stimulates mixed muscle protein synthesis rate in both the young and the old, although this is not demonstrated when myofibrillar protein synthesis is measured. Muscle is composed of several types of proteins, and their turnover may be differentially regulated. It is important, therefore, to measure the turnover of specific proteins such as myosin and actin, which are important contractile proteins. Recently, techniques have been developed to measure the synthesis rate of myosin heavy chain (MHC) in humans. In addition, the application of quantitative polymerase chain reaction (PCR) allows measurement of the steady state mRNA levels of various isoforms of MHC. These measurements, in combination with measurement of the synthesis rate of MHC, will allow us to understand the molecular regulation of specific proteins such as myosin. The important question is to determine whether the decline in muscle protein synthesis is genetically determined or secondary to inactivity, nutritional, hormonal, or other age-related alterations in body functions, and whether muscle wasting is reversible.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗

PubMed1980

Leucine oxidation and protein turnover in clofibrate-induced muscle protein degradation in rats.

Treatment of hyperlipidemia with clofibrate may result in development of a muscular syndrome. Our previous investigation (1979. J. Clin. Invest.64: 405.) showed that chronic administration of clofibrate to rats causes myotonia and decreases glucose and fatty acid oxidation and total protein of skeletal muscle. In the present experiments we have investigated amino acid and protein metabolism in these rats. Clofibrate administration decreased the concentration of all three branched-chain amino acids without affecting those of others in muscle. Studies to examine the mechanism of decreases in muscle concentrations of branched-chain amino acids showed the following: (a) Plasma concentration of leucine was decreased, whereas there was no significant change in the concentration of isoleucine and valine. (b) Liver concentrations of all three branched-chain amino acids remained unaltered. (c) The uptake of cycloleucine (a nonmetabolizable analogue of leucine) by both muscle and liver was unaffected. (d) The percentage of a trace amount of injected [1-(14)C]leucine expired as (14)CO(2) in 1 h was significantly increased. (e) The capacity of muscle homogenate for alpha-decarboxylation of leucine was enhanced, whereas that of liver was unaffected. (f) The activity of leucine transaminase was unaffected, whereas that of alpha-ketoisocaproate dehydrogenase was increased in muscle. Studies of protein synthesis, carried out as incorporation of leucine into protein and corrected for differences in specific activity, showed no alteration in liver but enhanced synthesis in muscle of clofibrate-fed rats. Clofibrate stimulated muscle protein degradation, which was demonstrated by increased tyrosine release from gastrocnemius muscle slices and by increased urinary excretion of 3-methylhistidine. We conclude that (a) clofibrate treatment increased branched-chain amino acid oxidation by increasing the activity of branched-chain alpha-ketoacid dehydrogenase in the muscle, (b) increased oxidation results in selective decreases in the concentration of these amino acids in muscle, and (c) decreases in branched-chain amino acid concentration may be responsible for increased protein degradation in muscle.

Administration, Oral↗

PubMed1983

Muscle protein turnover in uremia.

Abnormalities of muscle protein stores in uremia result from changes in the components of protein turnover. In vivo measurements of protein synthesis and degradation in uremia are subject to several errors. There may be incomplete equilibration of the infused labeled amino acid with the precursor pool for protein synthesis because of abnormal amino acid transport into muscle and increased catabolism of the infused amino acid. The infusion technique for measuring protein degradation cannot differentiate between rates occurring in different tissues. Moreover, measurement of 3-methylhistidine as an estimate of muscle protein degradation is invalid in uremia because its renal clearance is impaired. In vitro studies using radiolabeled amino acids should give more reliable estimates of the components of muscle protein turnover. Estimation of the rate of protein synthesis with a labeled amino acid still requires measurements of its specific activity in the precursor pool for protein synthesis, but this can be accomplished more easily in vitro. The factors known to affect protein synthesis and degradation in normal muscle, which are most likely to affect protein turnover in uremic muscle, are insulin-resistance and maladaptation to fasting. Few studies of the components of protein turnover in uremia have examined the effect of these or other factors.

Amino Acids↗

PubMed1996

The effect of endotoxin on skeletal muscle protein gene expression in the rat.

Sepsis is associated with net breakdown of skeletal muscle protein, mediated partly by reduced rates of muscle protein synthesis. This study investigated the role of altered gene expression for specific muscle proteins in mediating reduced protein synthesis in a rat model of acute severe sepsis. Adult rats were given a single sublethal intraperitoneal dose of endotoxin (bacterial lipopolysaccharide). Protein, RNA and DNA contents of muscle were measured and changes in expression of mRNA in tibialis anterior and extensor digitorum longus muscles were detected by quantification of Northern blots at 6, 24, 48 and 72 hr after endotoxin and in animals starved for 24 hr. Results showed that at 24 hr after endotoxin there was a loss of about 14% of muscle protein content. No reduction in mRNA was found at any time point for beta-myosin heavy chain (MHC), fast-MHC, alpha-actin, skeletal muscle troponin or carbonic anhydrase III (CA III); rather, at 48 hr there was increased expression of beta-MHC (224 +/- 123% control) and CA III (202 +/- 56%). Blocking TNF-alpha by pre-treatment with a monoclonal antibody did not appear to influence this. Total RNA content of muscle was reduced to 67% of the control values 24 hr after LPS, although this was no different to pair-fed animals starved for 24 hr. It is concluded that reduced protein synthesis in skeletal muscle in early acute sepsis is not primarily associated with reduced muscle protein gene expression.

Actins↗

PubMed1988

Reduction of muscle protein degradation by leupeptin in acutely uremic rats.

Enhanced muscle protein breakdown has been demonstrated in acutely uremic rats by numerous authors. These findings have been used to explain the clinical signs of muscle wasting and enhanced urea-N appearance, frequently observed in patients suffering from uremia. In order to investigate whether inhibition of skeletal muscle proteinases would have a favourable effect on the extent of muscle protein degradation, leupeptin, a low-molecular-weight proteinase inhibitor, was administered intraperitoneally to acutely uremic rats. 24 h after bilateral nephrectomy, leupeptin-treated animals displayed significantly lowered serum urea levels (-32%), and hence decreased urea-N appearances (-39%) as compared to untreated uremic rats. As a sign of muscle protein breakdown, plasma levels of Nt-methylhistidine, an indicator of myofibrillar protein degradation, were also decreased (-35%) in the uremic animals treated with leupeptin as compared to untreated uremic rats. Finally, leupeptin treatment resulted in a significant inhibition of the myofibrillar alkaline proteinase activity, a proteinase which has been related to various catabolic conditions. These findings suggest that the increased muscle protein breakdown in uremia is caused by enhanced activity of muscular proteinases and that antiproteolytic agents display favourable effects on the enhanced protein degradation observed in acute uremia.

Acute Disease↗

PubMed1992

Short-term starvation decreases skeletal muscle protein synthesis rate in man.

The rate of protein synthesis in skeletal muscle was determined in the post-absorptive state and after 3 days of starvation in healthy volunteers. The flooding dose technique employing intravenous injection of (1-13C)leucine (0.05 g kg-1) was used and incorporation of isotope into muscle protein was measured by taking percutaneous biopsies at 0 and 90 min. Blood samples were taken during the incorporation period for assessment of the enrichment of the free amino acid precursor of protein synthesis. The median (25,75 quartiles) rate of muscle protein synthesis after an overnight fast was 2.03 (2.00,2.23) % days-1 when the precursor enrichment was obtained by measurement of the plasma alpha-ketoisocaproate, taken to be representative of muscle free leucine. Repeat measurements in the same subjects after 3 days of total starvation showed a decrease to 1.82 (1.57,2.05) % days-1. Rates calculated on the basis of the plasma leucine as precursor were 5% lower at both times. An interindividual variation in response to starvation was observed, but the median decrease of 13% in the rate of protein synthesis was statistically significant (P less than 0.01).

Adult↗

PubMed2002

Insulin and amino acids independently stimulate skeletal muscle protein synthesis in neonatal pigs.

Infusion of physiological levels of insulin and/or amino acids reproduces the feeding-induced stimulation of muscle protein synthesis in neonates. To determine whether insulin and amino acids independently stimulate skeletal muscle protein synthesis in neonates, insulin secretion was blocked with somatostatin in fasted 7-day-old pigs (n = 8-12/group) while glucose and glucagon were maintained at fasting levels and insulin was infused to simulate either less than fasting, fasting, intermediate, or fed insulin levels. At each dose of insulin, amino acids were clamped at either the fasting or fed level; at the highest insulin dose, amino acids were also reduced to less than fasting levels. Skeletal muscle protein synthesis was measured using a flooding dose of l-[4-(3)H]phenylalanine. Hyperinsulinemia increased protein synthesis in skeletal muscle during hypoaminoacidemia and euaminoacidemia. Hyperaminoacidemia increased muscle protein synthesis during hypoinsulinemia and euinsulinemia. There was a dose-response effect of both insulin and amino acids on muscle protein synthesis. At each insulin dose, hyperaminoacidemia increased muscle protein synthesis. The effects of insulin and amino acids on muscle protein synthesis were largely additive until maximal rates of protein synthesis were achieved. Amino acids enhanced basal protein synthesis rates but did not enhance the sensitivity or responsiveness of muscle protein synthesis to insulin. The results suggest that insulin and amino acids independently stimulate protein synthesis in skeletal muscle of the neonate.

Amino Acids↗

PubMed2004

Age-related differences in skeletal muscle protein synthesis: relation to markers of immune activation.

Aging is associated with decreased skeletal muscle mass and function. These changes are thought to derive, in part, from a reduction in skeletal muscle protein synthesis. Although some studies have shown reduced postabsorptive muscle protein synthesis with age in humans, recent studies have failed to find an age effect. In addition to this disparity, few studies have attempted to characterize the hormonal factors that may contribute to changes in protein synthesis. Thus we examined the effect of age on skeletal muscle protein metabolism, with a specific emphasis on myosin heavy chain (MHC) protein, and the relationship of protein synthesis rates to plasma hormone levels. We measured body composition, muscle function, muscle protein synthesis, MHC and actin protein content, MHC isoform distribution, and plasma concentrations of cytokines and insulin-like growth factor-I (IGF-I) in 7 young [29 +/- 2 (SE) yr] and 15 old (72 +/- 1 yr; P < 0.01) volunteers. Mixed-muscle (-19%; P = 0.11), MHC (-22%; P = 0.08), and nonmyofibrillar (-17%; P = 0.10) protein synthesis all tended to be lower in old volunteers. Old volunteers were characterized by increased circulating tumor necrosis factor-alpha receptor II (P < 0.05) and reduced IGF-I (P < 0.01). In addition, plasma C-reactive protein, interleukin-6, and tumor necrosis factor-alpha receptor II concentrations were negatively related to mixed-muscle and MHC protein synthesis rates (range of r values: -0.422 to -0.606; P < 0.05 to <0.01). No differences in MHC or actin protein content were found. Old volunteers showed reduced (P < 0.05) MHC IIx content compared with young volunteers but no differences in MHC I or IIa. Our data show strong trends toward reduced postabsorptive muscle protein synthesis with age. Moreover, reduced muscle protein synthesis rates were related to increased circulating concentrations of several markers of immune activation.

Adult↗

PubMedDate not supplied

The use of a constant infusion of [3H]phenylalanine to measure the effects of glutamine infusions on muscle protein synthesis in rats given turpentine.

Skeletal muscle protein fractional synthetic rate (MPFSR) was measured in rats with a constant infusion of [3H]phenylalanine to study the relationship between the rate of muscle protein synthesis in skeletal muscle and the intracellular glutamine concentration. The values for MPFSR (percentage per day) achieved in this study were in good agreement with those we have already reported with a flooding dose of [3H]phenylalanine to measure MPFSR. This was the case both for control rats and for those that had been injected with turpentine (constant infusion 12.82 +/- 0.43% in saline-injected rats, 6.58 +/- 0.34% in rats injected with turpentine; flooding dose 12.88 +/- 0.73% in saline-injected rats, 7.04 +/- 0.67% in rats injected with turpentine). Therefore, there was no evidence for a stimulating effect of a flooding dose of phenylalanine on MPFSR, an effect that could have invalidated the conclusions drawn in our previous investigation. In this study, turpentine reduced the MPFSR by a mean of 49% (p < 0.001). This reduction in MPFSR was associated with a 39% reduction in the mean intramuscular glutamine concentration (p < 0.001). This reduction in MPFSR was associated with a 39% reduction in the mean intramuscular glutamine concentration (p < 0.001). The reduction in intramuscular glutamine concentration was completely reversed by 5-h intravenous infusions of 0.22 M glutamine solutions, but there was no accompanying increase in the MPFSR. The results of this study therefore provide no evidence to support the proposal that an acute change in intramuscular glutamine concentration is a major factor in controlling the rate of protein synthesis in skeletal muscle.

Animals↗

PubMed1992

Muscle protein synthesis is impaired in nephrotic rats.

Muscle protein synthesis is impaired in nephrotic rats: muscle and hepatic protein synthesis was measured as the incorporation of [3H]phenylalanine [3H]phe) into muscle and liver in male Sprague-Dawley rats with passive Heymann nephritis (HN) in comparison to both normal male (SDM) and female Sprague-Dawley rats (SDF). Incorporation of [3H]phe was significantly less muscle in HN (1.55 +/- 0.08 x 10(4) cpm/g muscle/h) than in SDM (2.55 +/- 0.14 x 10(4), p < 0.01) and no different than in SDF (1.64 +/- 0.23 x 10(4)). Growth rate was also significantly less in SDF and HN compared to SDM. Total [3H]phe incorporation and the % of [3H]phe incorporated into muscle correlated inversely with urinary albumin excretion in HN (p < 0.01) but not with serum albumin. In contrast, [3H]phe incorporation was increased in livers of HN (13.89 +/- 0.99 x 10(3) cpm/g rat/h) compared to either SDM (5.96 +/- 0.38 x 10(3), p < 0.01) or SDF (4.71 +/- 0.35 x 10(3), p < 0.01). Total liver mass, liver protein content, and the ratio of liver weight/body weight were all increased in HN. There were no differences in liver weight, liver protein content, or the ratio of liver weight/body weight between SDM and SDF. We have previously shown that decreased muscle protein accrual in HN cannot be overcome by increasing dietary protein intake. Hepatic protein synthesis and mass are increased in proteinuric rats while muscle protein synthesis is reduced. As a consequence growth rate and muscle protein accrual are diminished in nephrosis. The mechanism responsible for reduced muscle protein synthesis in the nephrotic syndrome is unknown.

Animals↗

PubMed1993

Acute response of human muscle protein to catabolic hormones.

OBJECTIVE: The purpose of this study was to determine the acute in vivo response of human muscle protein to stress. SUMMARY BACKGROUND DATA: Prior animal and human in vitro studies have suggested that physiologic stress increases muscle protein turnover. In contrast, recent publications using a polyribosomal methodology have demonstrated a reduction in human muscle protein synthesis in vivo after surgery. METHODS: Five healthy volunteers were given a stable isotopic infusion of 1,2(13)C leucine that allowed for determination of the fractional rate of muscle protein synthesis by measuring the rate of incorporation of 13C label into vastus lateralis muscle biopsies. Simultaneous infusion of 15N lysine and quantitation of leg blood flow by indocyanine green dye dilution allowed for estimation of leg muscle protein breakdown rate (Lys Ra) and synthesis rate (Lys Rd). These measurements were performed before and then at the conclusion of a 4-hour femoral arterial infusion of the catabolic hormones epinephrine, cortisol, and glucagon. RESULTS: The catabolic hormone infusion elicited a significant (65%) increase in the leg muscle protein breakdown rate and a significant but less marked increase in the rate of muscle protein synthesis, as assessed by both an increase in the fractional rate of muscle protein synthesis of 48.5% and in lysine uptake within the leg of 32%. CONCLUSIONS: This study conclusively demonstrates that a hormonally induced stress results in a net catabolism of human muscle protein by increasing the rate of protein breakdown in excess of an increased protein synthetic rate.

Adult↗

PubMedDate not supplied

[Effect of prolonged cold storage and subsequent heat treatment on the fractional composition of fish muscle proteins].

The effect of prolonged preservation at -18 degrees C and subsequent culinary heat treatment of the fractional composition of sarcoplasmatic and myofibrillar proteins in the muscles of mirror carp, pike and sheat-fish were studied by the method of gel-filtration on Sephadex G-100. Cold storage of the dish at -18 degrees C for 9 months was found to produce market changes in the qualitative and quantitative composition of muscle proteins. After culinary heat treatment the finished products have lost much of their original quality.

Animals↗