scholarly journals Role of protein degradation in the growth of livers after a nutritional shift

1976 ◽  
Vol 158 (2) ◽  
pp. 385-390 ◽  
Author(s):  
R D Conde ◽  
O A Scornik
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Liver Protein ◽  
Protein Ratio ◽  
Liver Growth ◽  
Adequate Diet ◽  
Rapid Restoration ◽  
The Difference ◽  
Net Protein

Fractional rates of synthesis and degradation of liver porteins were estimated during the rapid restoration of liver mass observed in protein-depleted mice when they are fed with an adequate diet. 1. Net protein gain was fastest 12h after the nutritional shift, when it reached a rate of 48% per day. 2. The RNA/protein ratio in livers of protein-depleted animals was essentially the same as in normal livers; it increased by a maximum of 13% 12h after the nutritional shift. 3. Rates of protein synthesis in vivo were measured by the incorporation into liver protein of massive amounts of L-[1-14C]leucine. In protein-depleted animals, the rate of synthesis per mg of RNA was 72% of that in normal livers. Normal rates were recovered within 12h of the nutritional shift. 4. The fraction of newly synthesized protein retained by the liver was studied after they were pulse-labelled by the intravenous injection of radioactive leucine, and, 5 min later, pactamycin (an inhibitor of the initiation of protein synthesis); 3h later the livers in both experimental situations retained 58% of the newly synthesized protein. 5. Fractional rates of protein degradation were estimated either from the difference between the synthesis of stable liver proteins and the net protein increase, or by the disappearance of radioactivity from the liver protein previously labelled by the administration to the mice of NaH14CO3. Both procedures demonstrated a large decrease in the rate of protein degradation during liver growth.

Decreased rate of protein breakdown during nutritional recovery of mouse kidney

1982 ◽  
Vol 243 (5) ◽  
pp. E360-E364
Author(s):  
J. A. Bur ◽  
R. D. Conde
Keyword(s):  
Protein Degradation ◽  
Normal Values ◽  
Normal Diet ◽  
Protein Mass ◽  
Nutritional Recovery ◽  
Complete Diet ◽  
Degradation Rates ◽  
The Difference ◽  
Net Protein

After a 5-day protein-depletion diet, there is a 23% decrease in kidney protein content in mice. When mice are shifted to a normal diet, protein mass is restored to its normal value 15 h after the nutritional change. The mechanism for this protein-depleted mice have a protein synthesis efficiency in vivo equal to 71% of that in normal kidneys, and normal values were reached within 6 h after the nutritional shift; 2) protein degradation rates were estimated either from the difference between the synthesis of kidney proteins and the net protein increase or by the disappearance of radioactivity from kidney proteins previously labeled by the administration of NaH14CO3 to mice. By both procedures, a large decrease in protein degradation rates during the recovery through a complete diet was observed.

Turnover of total proteins and ornithine aminotransferase during liver regeneration in rats

1980 ◽  
Vol 238 (1) ◽  
pp. E46-E52
Author(s):  
S. L. Augustine ◽  
R. W. Swick
Keyword(s):  
Amino Acids ◽  
Liver Regeneration ◽  
Protein Degradation ◽  
Partial Hepatectomy ◽  
Free Amino ◽  
Liver Protein ◽  
Ornithine Aminotransferase ◽  
Fractional Rate

The recovery of approximately 40% of the total liver protein during the first day after partial hepatectomy was shown to be due to the near cessation of protein breakdown rather than to an increase in protein synthesis. The decrease in degradation of total protein was less if rats were adrenalectomized or protein-depleted prior to partial hepatectomy. The effect of these treatments originally suggested that changes in free amino acid levels in liver might be related to the rate of protein degradation. However, no correlation was found between levels of total free amino acids and rates of breakdown. Measurements of individual amino acids during liver regeneration suggested that levels of free methionine and phenylalanine, amino acids that have been found to lower rates of protein degradation in vitro, are not correlated with rates of breakdown in vivo. The difference between the fractional rate of ornithine aminotransferase degradation (0.68/day and 0.28/day in sham-hepatectomized and partially hepatectomized rats, respectively) was sufficient to account for the higher level of this protein 3 days after surgery in the latter group.

Regulation of hepatic protein synthesis in chronic inflammation and sepsis

1992 ◽  
Vol 262 (2) ◽  
pp. C445-C452 ◽  
Author(s):  
T. C. Vary ◽  
S. R. Kimball
Keyword(s):  
Protein Synthesis ◽  
Sterile Inflammation ◽  
Chain Elongation ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Translational Efficiency ◽  
Liver Protein ◽  
Ribosomal Subunits ◽  
Hepatic Protein Synthesis

The regulation of protein synthesis was determined in livers from control, sterile inflammatory, and septic animals. Total liver protein was increased in both sterile inflammation and sepsis. The rate of protein synthesis in vivo was measured by the incorporation of [3H]phenylalanine into liver proteins in a chronic (5 day) intra-abdominal abscess model. Both sterile inflammation and sepsis increased total hepatic protein synthesis approximately twofold. Perfused liver studies demonstrated that the increased protein synthesis rate in vivo resulted from a stimulation in the synthesis of both secreted and nonsecreted proteins. The total hepatic RNA content was increased 40% only in sterile inflammation, whereas the translational efficiency was increased twofold only in sepsis. The increase in translational efficiency was accompanied by decreases in the amount of free 40S and 60S ribosomal subunits in sepsis. Rates of peptide-chain elongation in vivo were increased 40% in both sterile inflammation and sepsis. These results demonstrate that sepsis induces changes in the regulation of hepatic protein synthesis that are independent of the general inflammatory response. In sterile inflammation, the increase in protein synthesis occurs by a combination of increased capacity and translational efficiency, while in sepsis, the mechanism responsible for accelerated protein synthesis is an increased translational efficiency.

scholarly journals Key role of l-alanine in the control of hepatic protein synthesis

1987 ◽  
Vol 241 (2) ◽  
pp. 491-498 ◽  
Author(s):  
D Pérez-Sala ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Physiological Role ◽  
Chain Elongation ◽  
Liver Protein ◽  
Isolated Liver Cells ◽  
Metabolic Transformation ◽  
Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

scholarly journals Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

1980 ◽  
Vol 186 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Liver Protein ◽  
Isolated Cells ◽  
Isolated Liver Cells ◽  
Rat Liver Cells ◽  
Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

In vivo measurements of the contributions of protein synthesis and protein degradation in regulating cardiac pressure overload hypertrophy in the mouse

2012 ◽  
Vol 367 (1-2) ◽  
pp. 205-213 ◽  
Author(s):  
Paul J. McDermott ◽  
Catalin F. Baicu ◽  
Shaun R. Wahl ◽  
An O. Van Laer ◽  
Michael R. Zile
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Pressure Overload ◽  
In Vivo Measurements

scholarly journals The effect of denervation on protein synthesis and degradation in adult rat diaphragm muscle

2009 ◽  
Vol 107 (2) ◽  
pp. 438-444 ◽  
Author(s):  
Heather M. Argadine ◽  
Nathan J. Hellyer ◽  
Carlos B. Mantilla ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Caspase 3 ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Ubiquitin Proteasome Pathway ◽  
Protein Ubiquitination ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway ◽  
Net Protein

Previous studies showed that unilateral denervation (DNV) of the rat diaphragm muscle (DIAm) results in loss of myosin heavy chain protein by 1 day after DNV. We hypothesize that DNV decreases net protein balance as a result of activation of the ubiquitin-proteasome pathway. In DIAm strips, protein synthesis was measured by incorporation of 3H-Tyr, and protein degradation was measured by Tyr release at 1, 3, 5, 7, and 14 days after DNV. Total protein ubiquitination, caspase-3 expression/activity, and actin fragmentation were analyzed by Western analysis. We found that, at 3 days after DNV, protein synthesis increased by 77% relative to sham controls. Protein synthesis remained elevated at 5 (85%), 7 (53%), and 14 days (123%) after DNV. At 5 days after DNV, protein degradation increased by 43% relative to sham controls and remained elevated at 7 (49%) and 14 days (74%) after DNV. Thus, by 5 days after DNV, net protein balance decreased by 43% compared with sham controls and was decreased compared with sham at 7 (49%) and 14 days (72%) after DNV. Protein ubiquitination increased at 5 days after DNV and remained elevated. DNV had no effect on caspase-3 activity or actin fragmentation, suggesting that the ubiquitin-proteasome pathway rather than caspase-3 activation is important in the DIAm response to DNV. Early loss of contractile proteins, such as myosin heavy chain, is likely the result of selective protein degradation rather than generalized protein breakdown. Future studies should evaluate this selective effect of DNV.

scholarly journals Effect of a nutritional shift on the degradation of abnormal proteins in the mouse liver. Decreased degradation during rapid liver growth

1977 ◽  
Vol 164 (2) ◽  
pp. 363-369 ◽  
Author(s):  
R Amils ◽  
R D Conde ◽  
O A Scornik
Keyword(s):  
Protein Degradation ◽  
Size Distribution ◽  
Intravenous Injection ◽  
Mouse Liver ◽  
Liver Protein ◽  
Large Decrease ◽  
General Phenomenon ◽  
Liver Growth ◽  
Selective Degradation ◽  
Total Liver

1. The intravenous injection of puromycin to mice 0.5 min after administration of radioactive leucine resulted in the release of labelled ribosome-bound nascent protein chains with the next 0.5 min. 2. During the subsequent 13 min, 40% of the liver protein radioactivity disappeared. The rate of this process was already maximal 0.5 min after the injection of puromycin, with no apparent lag. 3. Evidence is presented that this phenomenon represents the selective degradation of puromycinyl-peptides: (a) the magnitude of this fraction corresponded to the calculated proportion of protein radioactivity in nascent chains at the time of the puromycin effect; (b) the size distribution of the proteins disappearing between 2 and 14 min was smaller than that of those retained at 14 min; and (c) when the injection of puromycin was delayed for 5 min, or when the leucine pulse was interrupted by the injection of cycloheximide (rather than puromycin), the fraction disappearing within 14 min was much smaller. 4. The degradation of puromycinyl-peptides was much slower in the rapidly growing livers of animals recovering from a protein depletion than in the protein-depleted controls. It is concluded that the large decrease in the overall rates of total liver protein degradation previously described during liver growth is a general phenomenon, also affecting the rate of scavenging of abnormal proteins.

Changes in protein turnover in rat uterus during pregnancy

1986 ◽  
Vol 250 (2) ◽  
pp. E114-E120 ◽  
Author(s):  
A. J. Morton ◽  
D. F. Goldspink
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Protein Turnover ◽  
Cathepsin D ◽  
Cell Loss ◽  
Protein Breakdown ◽  
Rat Uterus ◽  
Fractional Rate ◽  
Uterine Growth

The adaptive growth and protein turnover of the rat uterus were studied during the 21 days of gestation and up to 3 days after parturition. Despite large increases (13-fold) in uterine size during gestation, the fractional rate of protein synthesis (measured in vivo) remained unchanged when compared with nonpregnant tissue values of 44 +/- 5%/day. However, decreases were found in the rate of protein breakdown after implantation (i.e., 75% on day 7 and 28% on day 11) and in the activity of cathepsin D (i.e., 33 and 85% on days 8 and 16 of gestation). Changes in the degradative processes would therefore appear to be primarily responsible for the massive uterine growth during pregnancy. In contrast to the uterus the fractional rates of synthesis in the placenta and fetus progressively decreased during gestation. After parturition the uterus rapidly returned to its normal size by a combination of cellular atrophy and cell loss. After 2 days, a complementary decrease in the fractional rate of synthesis (30%) and an increase in protein degradation (2-fold) explained the process of involution.

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.

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