Measurement of protein turnover in rat liver. Analysis of the complex curve for decay of label in a mixture of proteins

Garlick, Peter J.; Waterlow, J. C.; Swick, Robert W.

doi:10.1042/bj1560657

Cited by 79 publications

(34 citation statements)

References 19 publications

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“…In man, rates of tissue protein synthesis have been measured in biopsy samples of muscle from normal volunteers or patients with muscular diseases Rennie, Edwards, Millward, Wolman, Halliday & Matthews, 1982b); and in muscle, liver, intestine and tumours, in samples removed at operation (Stein, Mullen, Oram-Smith, Rosato, Wallace & Hargrove, 1978 (Garlick, Waterlow & Swick, 1976 (Swick, 1981).…”

Section: Measurement Ofprotein Turnover Rates In Individual Tissuesmentioning

confidence: 99%

Protein Turnover With Special Reference to Man

1984

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This review is concerned with rates of N flux in the living animal rather than with mechanisms of protein synthesis and breakdown at the cellular level. Methods of measuring protein turnover in the whole body are discussed, with special emphasis on studies in man, and results obtained by different methods have been compared. Aspects of whole body protein turnover which are of physiological interest include its relation to body size, growth and development, energy metabolism and food intake. There are substantial increases in protein turnover in injury, and changes that occur in exercise are beginning to be explored. From the physiological point of view these results point the need for future research along two main lines. The first is that of regulation: a wide variety of hormones stimulate or repress protein synthesis and breakdown, with varying actions in different tissues. These effects, however, do not in themselves explain the mechanism by which a balance between synthesis and breakdown is maintained. Secondly, the fact that all cellular proteins are in a dynamic state poses questions about the relation between structure and function in tissues such as muscle and brain, which physiologists have hardly begun to tackle.

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Section: Measurement Ofprotein Turnover Rates In Individual Tissuesmentioning

confidence: 99%

Protein Turnover With Special Reference to Man

1984

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“…52 Total glycoprotein synthesis was found to be responsible for 6%-10% of total tracer incorporation in the mucosa, 53 whereas in rat liver about 10% of all proteins show a rapid turnover in the above range. 37,41 Our calculation of a size of 4% for such a rapidly turning over protein pool in human postoperative ileal mucosa would be in the range of these estimates and would, therefore, also support the validity of the rapidly turning over pool concept for explaining the enrichment changes that were seen during continuous isotope infusion over prolonged periods of time in ileal mucosa from controls. …”

Section: Resultsmentioning

confidence: 62%

“…It is obvious that turnover of individual proteins varies between a few minutes and many days. 37,40,41 Therefore, the time will also vary after which all proteins in a specific pool will be labeled during a continuous tracer infusion and at which point the isotopic plateau is being reached. Beyond that point, only those individual proteins or protein pools will add to the rising enrichment of the total pool that have not yet reached their isotopic plateau.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Hyperglycemic Hyperinsulinemia on Small‐Intestinal Mucosal Protein Synthesis in Patients After Surgical Stress

Rittler

Schiefer

Demmelmair

et al. 2006

J Parenter Enteral Nutr

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Hyperglycemic hyperinsulinemia cannot stimulate intestinal protein synthesis in healthy individuals but does so in conditions characterized by an altered somatotropic axis such as diabetes. Only in a state of growth hormone resistance (high growth hormone but low insulin like growth factor [IGF‐1] concentrations), extra insulin may acutely reverse the impaired, growth‐hormone‐induced IGF‐1 release, thereby exerting anabolic actions at the intestinal tract. Growth hormone resistance can be also found in patients after surgical stress. Therefore, we wanted to test the hypothesis whether hyperglycemic hyperinsulinemia would stimulate ileal protein synthesis in the latter condition. Mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) were used to directly determine the incorporation rate of 1‐[13C]‐leucine into ileal mucosal protein. All subjects had an ileostomy, which allowed easy access to the ileal mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 μmol/kg min). Isotopic enrichments and fractional protein synthesis were determined at baseline (period I) and after a 4‐hour glucose infusion (170 mg/kg/h) or after infusion of saline (control group) (period II). In controls, ileal protein synthesis declined significantly during prolonged isotope infusion (period I: 1.11± 0.14%/h, period II: 0.39 ± 0.13%/h, p < .01). In contrast, ileal protein synthesis remained constant during glucose infusion (period I: 1.32 ± 0.35%/h, period II: 1.33 ± 0.21%/h, n.s. vs period I, but p < .005 vs the corresponding value at the end of period II in the control group). Using the continuous tracer infusion technique, ileal protein synthesis seemingly declines over a short time in control subjects. We found evidence that this artificial decline was due to mass effects of a rapidly turning over mucosa protein pool in which an isotopic plateau was reached during the experiment and of which the size amounted to approximately 4% of the total mixed protein pool. Maintenance of ileal protein synthesis during glucose infusion therefore indicates a rise of ileal protein synthesis in a slowly turning over protein pool. This effect in postsurgical patients would be compatible with the concept of intestinal insulin action to depend on the specific clinical state (eg, growth hormone resistance).

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“…18 -22 Nevertheless, because the size of this specific pool amounts to Ͻ10% of the total protein pool, [23][24][25] the vast majority of proteins can still be studied in tracer infusion experiments such as ours.…”

Section: July-august 2005mentioning

confidence: 99%

Effect of Amino Acid Infusion on Human Postoperative Colon Protein Synthesis in Situ

Rittler

Schiefer

Demmelmair

et al. 2005

J Parenter Enteral Nutr

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ABSTRACT. Background: Amino acids are an integral part of parenteral nutrition because of their anabolic action helping to conserve body protein after surgical stress. At the gastrointestinal tract, an adequate supply of amino acids may be particularly important because of the gut's high rate of protein turnover, cell division, and proliferation. However, no information is available about the effects of amino acids on human intestinal protein metabolism after surgery. Methods: Studies were performed in postabsorptive patients 8 -10 days after major abdominal surgery. Mass spectrometry techniques (capillary gas chromatography/ combustion isotope ratio mass spectrometry) were used to directly determine the incorporation rate of 1-[13 C]-leucine into colon mucosal protein. All subjects had a colostomy, which allowed easy access to the colon mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 mol/kg min). Isotopic enrichments were determined at baseline and after a 4-hour infusion of amino acids or after infusion of saline (control group). Results: Compared with baseline, infusion of amino acids reduced fractional colon protein synthesis significantly by Ϫ29.2 Ϯ 8.3%. This decrease was also significantly different from the corresponding (insignificant) change during saline infusion (ϩ19.4 Ϯ 26.9%, p Ͻ .05 vs amino acid group). Conclusions: After surgery, an amino acid infusion acutely reduces postoperative colon protein synthesis. This effect possibly may be attributed to interactions of specific amino acids (glutamine) with an altered intestinal immune system and enterocyte activity. Amino acid supply has gained its firm place during parenteral nutrition in a wide range of patients who cannot tolerate enteral feeding. Amino acids are usually considered necessary to reduce protein loss after surgical stress. An optimal conservation of body protein will be obtained with daily administration of 1.2-1.5 g amino acids per kg body weight.1 Potential anabolic actions of amino acids are known to occur in muscle and in splanchnic tissues.2 At the intestinal tract, amino acid metabolism and protein turnover are particularly important because an efficient formation of new protein is essential for maintaining a high rate of cell division and proliferation and for the production of cellular structure compounds and secreted enzymes.3,4 Unfortunately, in humans effects of specific substrates have almost exclusively been studied in the whole splanchnic bed, not allowing a differentiation between hepatic and intestinal changes.5-7 Virtually nothing is known on the effects of amino acids on human intestinal protein metabolism in situ.We sought in the present study to examine the effects of a standard amino acid infusion on colon protein synthesis using stable isotopes (1-[ 13 C]-leucine) and advanced mass spectrometry techniques. Studies were performed in patients after major abdominal surgery whose mucosal function may be altered and who are frequent candidates for parenteral...

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Measurement of protein turnover in rat liver. Analysis of the complex curve for decay of label in a mixture of proteins

Cited by 79 publications

References 19 publications

Protein Turnover With Special Reference to Man

Protein Turnover With Special Reference to Man

The Effect of Hyperglycemic Hyperinsulinemia on Small‐Intestinal Mucosal Protein Synthesis in Patients After Surgical Stress

Effect of Amino Acid Infusion on Human Postoperative Colon Protein Synthesis in Situ

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