scholarly journals The effect of glucagon administration on protein synthesis in skeletal muscles, heart and liver in vivo

1985 ◽  
Vol 228 (3) ◽  
pp. 575-581 ◽  
Author(s):  
V R Preedy ◽  
P J Garlick
Keyword(s):  
Protein Synthesis ◽  
Skeletal Muscles ◽  
Plasma Insulin ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Diabetic Rats ◽  
Liver Protein ◽  
Food Absorption ◽  
Metabolic Stresses

Infusion of glucagon (0.5 mg/h per 100 g body wt.) into fed rats for 6 h inhibited protein synthesis in skeletal muscle, but not in heart. The order of sensitivity of three muscles was plantaris greater than gastrocnemius greater than soleus. Treatment with glucagon for periods of 1 h or less had no effect. Liver protein synthesis was inhibited by glucagon treatment for 10 min, but stimulated after 6 h. The effect of glucagon on muscle was not secondary to impaired food absorption or to depletion of amino acids by increased gluconeogenesis, since the inhibition of protein synthesis was observed in postabsorptive and amino acid-infused rats. The failure of glucagon to inhibit muscle protein synthesis after 1 h may have been caused by the increase in plasma insulin that occurred at this time, since an inhibition was detected in insulin-treated diabetic rats. The lowest infusion rate that gave a significant decrease in muscle protein synthesis was 6 micrograms/h per 100 g body wt., despite a small increase in plasma insulin. This gave plasma glucagon concentrations in the high pathophysiological range, suggesting that glucagon may be significant in the pathogenesis of muscle wasting in metabolic stresses such as diabetes and starvation.

Enhanced response of muscle protein synthesis and plasma insulin to food intake in suckled rats

1993 ◽  
Vol 265 (2) ◽  
pp. R334-R340 ◽  
Author(s):  
T. A. Davis ◽  
M. L. Fiorotto ◽  
H. V. Nguyen ◽  
P. J. Reeds
Keyword(s):  
Protein Synthesis ◽  
Food Intake ◽  
Plasma Insulin ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Fed State ◽  
Fasting And Refeeding ◽  
Old Rats ◽  
Amino Acid Concentrations

To compare the sensitivity of muscle protein synthesis to food intake in neonatal and weaned rats, 5- and 16-day-old suckled rats and 28-day-old weaned rats were either fed, fasted for 8-10 h, or refed for 1-4 h after an 8-h fast. Protein synthesis was measured in vivo in soleus and plantaris muscles with a large dose of L-[4-3H]phenylalanine. In fed rats, fractional rates of protein synthesis (KS) decreased with age. Fasting decreased KS, and refeeding increased KS most in 5-day-old animals, less in 16-day-old rats, and least in 28-day-old rats. In 5-day-old rats, there were no differences in KS between soleus and plantaris muscles in the fed state and after fasting and refeeding; at 28 days, KS was higher in soleus than in plantaris in fed rats, and the soleus did not respond to fasting and refeeding. In rats at all three ages, the concentration of most plasma amino acids decreased during fasting; when 5-day-old rats were refed, plasma amino acid concentrations increased, but not to the levels in the fed state. Plasma insulin concentrations increased with age. Plasma insulin concentrations decreased more rapidly with fasting and increased more extensively with refeeding in 5-day-old rats than in older rats. These results suggest that muscle protein synthesis is more responsive to food intake in young suckled rats than in older suckled or weaned rats; this increased responsiveness is accompanied by greater changes in circulating insulin concentrations.

Skeletal muscle, liver and wool protein synthesis by sheep infected by the nematode Trichostrongylus colubriformis

1975 ◽  
Vol 26 (6) ◽  
pp. 1063
Author(s):  
LEA Symons ◽  
WO Jones
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Trichostrongylus Colubriformis ◽  
Intestinal Nematode ◽  
Skeletal Muscle Proteins

Incorporation of radioisotopically labelled L-leucine into skeletal muscle proteins was measured in vivo and in vitro, and into liver proteins in vivo in three groups of sheep: (1) infected by Trichostrongylus colubriformis, (2) uninfected, pair-fed with the infected animals, (3) uninfected, fed ad lib. Incorporation of [14C]L-leucine by an homogenate of wool follicles from infected and uninfected sheep was also measured. Incorporation of leucine by muscle, and hence muscle protein synthesis, was equally depressed in the anorexic infected sheep losing weight, and in pair-fed animals, whether measured in vivo or in vitro, or expressed in terms of either RNA or DNA. Incorporation into protein was elevated equally in vivo in the livers of the infected and pair-fed sheep when expressed in terms of content of tissue nitrogen, but not in terms of cither nucleic acid. Incorporation by the wool follicular homogenate was appreciably depressed by the infection and is consistent with the poor wool growth in nematode infections. These results show that the same depression of skeletal muscle and, possibly, elevation of liver protein synthesis occur in a ruminant as were reported earlier for laboratory monogastric animals with intestinal nematode infections. Pair-feeding uninfected animals in both this and the earlier experiments emphasized the importance of anorexia as a major cause of these effects on protein synthesis. The importance of these effects upon production is discussed briefly.

scholarly journals Short-term effects of corticosterone treatment on muscle protein synthesis in relation to the response to feeding

1987 ◽  
Vol 248 (2) ◽  
pp. 439-442 ◽  
Author(s):  
P J Garlick ◽  
I Grant ◽  
R T Glennie
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Plasma Corticosterone ◽  
Male Rats ◽  
Liver Protein ◽  
Carrier Medium ◽  
Corticosterone Treatment ◽  
Small Inhibition

1. Rates of protein synthesis in liver and muscle of 100 g male rats were measured in vivo at 1 h or 4 h after injection of 2.5 mg of corticosterone and compared with those from animals given carrier medium alone. 2. In post-absorptive rats, corticosterone for 1 h had no effect on either muscle or liver protein synthesis. After 4 h there was a decrease in both tissues, but this was only statistically significant in muscle. 3. In fed rats, rates of protein synthesis were higher than those in post-absorptive animals, but the effects of corticosterone injection were similar. 4. Re-feeding of post-absorptive rats led to an increase in muscle protein synthesis after 1 h and 4 h. At 1 h this increase was not inhibited when plasma corticosterone concentrations were maintained high by injection of the hormone immediately before feeding commenced, but at 4 h there was a small inhibition. 5. It is concluded that the action of corticosterone in depressing muscle protein synthesis is time-dependent and requires longer than 1 h to develop. The failure of the hormone to alter the response to re-feeding for 1 h in post-absorptive rats suggest that corticosteroids are not important mediators of the acute stimulation of muscle protein synthesis by food intake.

Corrigendum - Skeletal muscle, liver and wool protein synthesis by sheep infected by the nematode Trichostrongylus colubriformis

1975 ◽  
Vol 26 (6) ◽  
pp. 1063
Author(s):  
LEA Symons ◽  
WO Jones
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Trichostrongylus Colubriformis ◽  
Intestinal Nematode ◽  
Skeletal Muscle Proteins

Incorporation of radioisotopically labelled L-leucine into skeletal muscle proteins was measured in vivo and in vitro, and into liver proteins in vivo in three groups of sheep: (1) infected by Trichostrongylus colubriformis, (2) uninfected, pair-fed with the infected animals, (3) uninfected, fed ad lib. Incorporation of [14C]L-leucine by an homogenate of wool follicles from infected and uninfected sheep was also measured. Incorporation of leucine by muscle, and hence muscle protein synthesis, was equally depressed in the anorexic infected sheep losing weight, and in pair-fed animals, whether measured in vivo or in vitro, or expressed in terms of either RNA or DNA. Incorporation into protein was elevated equally in vivo in the livers of the infected and pair-fed sheep when expressed in terms of content of tissue nitrogen, but not in terms of cither nucleic acid. Incorporation by the wool follicular homogenate was appreciably depressed by the infection and is consistent with the poor wool growth in nematode infections. These results show that the same depression of skeletal muscle and, possibly, elevation of liver protein synthesis occur in a ruminant as were reported earlier for laboratory monogastric animals with intestinal nematode infections. Pair-feeding uninfected animals in both this and the earlier experiments emphasized the importance of anorexia as a major cause of these effects on protein synthesis. The importance of these effects upon production is discussed briefly.

IGF-I stimulation of muscle protein synthesis in the awake rat: permissive role of insulin and amino acids

1996 ◽  
Vol 270 (1) ◽  
pp. E60-E66 ◽  
Author(s):  
R. Jacob ◽  
X. Hu ◽  
D. Niederstock ◽  
S. Hasan ◽  
P. H. McNulty ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Plasma Insulin ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Amino Acid Replacement ◽  
Igf I ◽  
Awake Rat

Infusion of insulin-like growth factor I (IGF-I) lowers plasma amino acid and insulin concentrations, which may limit the capacity of IGF-I to promote muscle protein synthesis in vivo. We measured heart and skeletal muscle incorporation of continuously infused L-[ring-2,6-3H]phenylalanine in awake postabsorptive rats receiving 4-h intravenous infusions of saline (n = 11), IGF-I (1 microgram.kg-1.min-1) with (n = 10) or without (n = 11) amino acid replacement, or IGF-I with insulin replacement (n = 8). There were no significant increases in muscle protein synthesis during the infusion of IGF-I alone, which was associated with decreases in both plasma insulin (52 +/- 5%, P < 0.001) and amino acids (25 +/- 5%, P < 0.05). When IGF-I was given together with amino acids, protein synthesis was significantly increased in gastrocnemius (4.7 +/- 0.4 vs. 2.5 +/- 0.3%/day, P < 0.001), oblique (4.5 +/- 0.4 vs. 2.8 +/- 0.4%/day, P < 0.05), and soleus (8.8 +/- 0.7 vs. 6.4 +/- 0.3%/day, P < 0.01) and tended to be higher than saline control values in heart (10.9 +/- 0.9 vs. 8.8 +/- 0.7%/day, P = 0.08). Amino acid replacement prevented plasma concentrations from falling and also blunted the decline in plasma insulin (22 +/- 5%, P < 0.01 vs. IGF-I alone). When IGF-I and insulin replacement were given, protein synthesis was increased in heart (13.0 +/- 0.6%/day), gastrocnemius (4.7 +/- 0.4%/day), and oblique (4.5 +/- 0.4%/day) (P < 0.001 for each, compared with saline). We conclude that the action of IGF-I to acutely stimulate muscle protein synthesis in the awake rat is limited by the fall in circulating insulin and/or amino acid concentrations that accompanies IGF-I infusion in vivo and is prevented by co-infusion of insulin or amino acids.

scholarly journals Muscle protein synthesis in the streptozotocin-diabetic rat. A possible role for corticosterone in the insensitivity to insulin infusion in vivo

1982 ◽  
Vol 202 (2) ◽  
pp. 363-368 ◽  
Author(s):  
B R Odedra ◽  
S S Dalal ◽  
D J Millward
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Insulin Infusion ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Pre Treatment ◽  
Adrenalectomized Rats

The effect of insulin infusion in vivo on muscle protein synthesis was investigated in rats. In 10-days-streptozotocin-diabetic rats infused in vivo with amino acids and glucose, the rate of protein synthesis per unit of RNA (RNA activity) was markedly decreased. Pre-treatment with large doses of insulin at 17 and 1 h before the infusion fully restored RNA activity to normal. Infusion of insulin for 6 h with amino acids and glucose did not restore RNA activity to normal in the diabetic rats. However, in diabetic-adrenalectomized rats similar infusions of insulin fully restored RNA activity to normal. Measurements of plasma corticosterone concentrations indicated a 50% increase in the diabetic rats. Since pre-treatment with corticosterone suppressed the stimulatory effect of insulin infusion on RNA activity in adrenalectomized rats, and since corticosterone treatment for 6 days suppressed RNA activity even though insulin concentrations were elevated, it is suggested that increased concentrations of corticosterone are responsible for the lag in response to insulin in the diabetic rat. This means that the catabolic effects of glucocorticoids must be also considered together with the catabolic effect of insulin lack in diabetes.

Sequential changes in in vivo muscle and liver protein synthesis and plasma and tissue glutamine levels in sepsis in the rat

2001 ◽  
Vol 101 (3) ◽  
pp. 295-304 ◽  
Author(s):  
Michael J. O'LEARY ◽  
Colin N. FERGUSON ◽  
Michael J. RENNIE ◽  
Charles J. HINDS ◽  
John H. COAKLEY ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Content ◽  
Total Protein ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Total Protein Content ◽  
Sham Operation ◽  
Liver Protein ◽  
Male Wistar Rats

We have investigated sequential changes in skeletal muscle and hepatic protein synthesis following sepsis, and their relationship to changes in circulating and tissue glutamine concentrations. Male Wistar rats underwent caecal ligation and puncture (CLP) or sham operation, with starvation, and were killed 24, 72 or 96 h later. A group of non-operated animals were killed at the time of surgery. Protein synthesis was determined using a flooding dose of l-[4-3H] phenylalanine, and glutamine concentrations were measured by an enzymic fluorimetric assay. Protein synthesis in gastrocnemius muscle fell in all groups. Gastrocnemius total protein content was reduced after CLP and at 72 and 96 h after sham operation. After CLP, protein synthesis was lower at 24 h, and total protein content was lower at 72 and 96 h, than in sham-operated animals. CLP was associated with increased liver protein synthesis at all time points, whereas there was no change after sham operation. Liver protein content did not change after CLP, but was lower at 72 and 96 h after sham operation than in non-operated animals. Plasma glutamine concentrations were reduced at 24 h after sham operation, and at 72 and 96 h after CLP. Muscle glutamine concentrations were reduced in all groups, with the decrease being greater following CLP than after sham operation. In the liver, glutamine concentrations were unchanged after CLP, but increased after sham operation. In rats with sepsis, decreases in muscle protein synthesis and content are associated with markedly reduced muscle glutamine concentrations. Plasma glutamine concentrations are initially maintained, but fall later. In liver, protein synthesis is increased, while glutamine concentrations are preserved. These results support a peripheral-to-splanchnic glutamine flux in sepsis.

scholarly journals Acute effects of corticosterone on tissue protein synthesis and insulin-sensitivity in rats in vivo

1990 ◽  
Vol 272 (1) ◽  
pp. 187-191 ◽  
Author(s):  
B G Southorn ◽  
R M Palmer ◽  
P J Garlick
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Optimal Time ◽  
Liver Protein ◽  
Time Period ◽  
Tissue Protein Synthesis ◽  
High Doses ◽  
Corticosterone Treatment

The effect of corticosterone treatment on the sensitivity of muscle protein synthesis to insulin infusion was assessed in post-absorptive young rats. To select the optimal time period for corticosterone treatment, protein synthesis was measured by injection of L-[2,6-3H]phenylalanine (1.5 mmol/kg body weight) 1, 4, 12 or 24 h after injection of corticosterone (5 mg/kg body wt.). Muscle protein synthesis was significantly decreased at 4 h and the effect was maximal by 12 h; liver protein synthesis was elevated at 12 h and 24 h. The dose-response of muscle protein synthesis to a 30 min infusion with 0-150 munits of insulin/h was then compared in rats pretreated with corticosterone (10 mg/100 g body wt.) or vehicle alone. When no insulin was infused, corticosterone inhibited protein synthesis in gastrocnemius muscle. High doses of insulin stimulated protein synthesis, but the inhibition by corticosterone was similar to that in the absence of insulin. At intermediate doses of insulin there was an increased requirement for insulin to elicit an equivalent response in muscle protein synthesis. Plantaris muscle responded in a manner similar to that of gastrocnemius, but neither soleus muscle nor liver responded significantly to insulin. These data suggest that corticosterone has two modes of action; one which is independent from and opposite to that of insulin, and a second which causes insulin-resistance through a decrease in sensitivity rather than a change in responsiveness.

scholarly journals The effect of glutamine on protein turnover in chick skeletal muscle in vitro

1990 ◽  
Vol 265 (2) ◽  
pp. 593-598 ◽  
Author(s):  
G Wu ◽  
J R Thompson
Keyword(s):  
Protein Synthesis ◽  
Skeletal Muscles ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Plasma Concentrations ◽  
Glutamine Concentration ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

The effect of glutamine on the rates of protein synthesis and degradation was studied in isolated chick extensor digitorum communis muscles incubated in the presence of plasma concentrations of amino acids. Addition of 0.5-15 mM-glutamine increases (P less than 0.01) intracellular glutamine concentrations by 31-670%. There is a positive relationship (r = 0.975, P less than 0.01) between intracellular glutamine concentration and the rate of muscle protein synthesis measured by the incorporation of [3H]phenylalanine. The stimulating effect of 15 mM-glutamine on protein synthesis was decreased from 58 to 19% in muscles incubated in the absence of tyrosine. The rates of protein degradation, estimated from [3H]phenylalanine release from muscle proteins prelabelled in vivo, decreased (P less than 0.05) by 15-30% in the presence of 4-15 mM-glutamine when compared with muscles incubated in the presence of physiological concentrations of glutamine (0.5-1 mM). Glutamine concentrations ranging from 2 to 15 mM appear to have an overall anabolic effect on chick skeletal muscles incubated in vitro.

Effect of nitrogen and calorie restriction on protein synthesis in the rat

1976 ◽  
Vol 230 (5) ◽  
pp. 1321-1325 ◽  
Author(s):  
TP Stein ◽  
JC Oram-Smith ◽  
MJ Leskiw ◽  
HW Wallace ◽  
LC Long ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Protein Catabolism ◽  
Intravenous Hyperalimentation ◽  
Major Response ◽  
Dietary Deficiency

The effect of a deficiency of calories and/or nitrogen on protein metabolism in the rat was investigated. During the 5 days of the study, the rats received all nutrients except water via intravenous hyperalimentation. Four diets were used: I) 1.25 g amino acids, 12.5 g glucose/day; II) 1.25 g amino acids/day; III) 1.25 g glucose/day; and IV) 12.5 glucose/day. The rate of protein synthesis in heart, lung, muscle, kidney, and liver was estimated by a modification of the technique of Garlick et al. (The diurnal response of muscles and liver protein synthesis in vivo in meal-fed rats. Biochem. J. 136: 935-945, 1973) except that [15N]glycine was used as the tracer. Heart and lung protein synthesis was depressed by both caloric and nitrogen restriction. Muscle protein synthesis was only significantly affected by omission of calories from the diet. Kidney nitrogen content increased with the amino acid diets and decreased with the nitrogen-deficient diets. The major response of the liver to a dietary deficiency was to lose nitrogen via an increase in the rate of liver protein catabolism.

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