Glutamine is considered to be a ‘conditionally’ essential amino acid. During situations of severe stress like sepsis or after trauma there is a fall in plasma glutamine levels, enhanced glutamine turnover and intracellular muscle glutamine depletion. Under these conditions, decreased intramuscular glutamine concentration correlates with reduced rates of protein synthesis. It has therefore been hypothesized that intracellular muscle glutamine levels have a regulatory role in muscle protein turnover rates. Administration of the glutamine synthetase inhibitor methionine sulphoximine (MSO) was used to decrease glutamine levels in male Wistar rats. Immediately after the MSO treatment (t = 0 h), and at t = 6 h and t = 12 h, rats received intraperitoneal injections (10 ml/100 g body weight) with glutamine (200 mM) to test whether this attenuated the fall in plasma and intracellular muscle glutamine. Control animals received alanine and saline after MSO treatment, while saline was also given to a group of normal rats. At t = 18 h rats received a primed constant infusion of l-[2,6-3H]phenylalanine. A three-pool compartment tracer model was used to measure whole-body protein turnover and muscle protein kinetics. Administration of MSO resulted in a 40% decrease in plasma glutamine and a 60% decrease in intracellular muscle glutamine, both of which were successfully attenuated by glutamine infusions. The decreased intracellular muscle glutamine levels had no effect on whole-body protein turnover or muscle protein kinetics. Also, glutamine supplementation did not alter these parameters. Alanine supplementation increased both hindquarter protein synthesis and breakdown but the net balance of phenylalanine remained unchanged. In conclusion, our results show that decreased plasma and muscle glutamine levels have no effect on whole-body protein turnover or muscle protein kinetics. Therefore, it is unlikely that, in vivo, the intracellular muscle concentration of glutamine is a major regulating factor in muscle protein kinetics.
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Research Article|
May 11 1999
Effects in vivo of decreased plasma and intracellular muscle glutamine concentration on whole-body and hindquarter protein kinetics in rats
Steven W. M. OLDE DAMINK;
Steven W. M. OLDE DAMINK
1Department of Surgery, Maastricht University, P. O. Box 616, NL-6200 MD Maastricht, The Netherlands
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Ivo DE BLAAUW;
Ivo DE BLAAUW
1Department of Surgery, Maastricht University, P. O. Box 616, NL-6200 MD Maastricht, The Netherlands
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Nicolaas E. P. DEUTZ;
1Department of Surgery, Maastricht University, P. O. Box 616, NL-6200 MD Maastricht, The Netherlands
Correspondence: Dr N. E. P. Deutz.
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Peter B. SOETERS
Peter B. SOETERS
1Department of Surgery, Maastricht University, P. O. Box 616, NL-6200 MD Maastricht, The Netherlands
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Publisher: Portland Press Ltd
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 1999
1999
Clin Sci (Lond) (1999) 96 (6): 639–646.
Citation
Steven W. M. OLDE DAMINK, Ivo DE BLAAUW, Nicolaas E. P. DEUTZ, Peter B. SOETERS; Effects in vivo of decreased plasma and intracellular muscle glutamine concentration on whole-body and hindquarter protein kinetics in rats. Clin Sci (Lond) 1 June 1999; 96 (6): 639–646. doi: https://doi.org/10.1042/cs0960639
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