Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids
Article first published online: 5 AUG 2004
The Journal of Physiology
Volume 532, Issue 2, pages 575–579, April 2001
How to Cite
Bohé, J., Low, J. F. A., Wolfe, R. R. and Rennie, M. J. (2001), Rapid Report. The Journal of Physiology, 532: 575–579. doi: 10.1111/j.1469-7793.2001.0575f.x
- Issue published online: 5 AUG 2004
- Article first published online: 5 AUG 2004
- (Received 15 January 2001; accepted after revision 22 February 2001)
- 1The aim of this study was to describe the time course of the response of human muscle protein synthesis (MPS) to a square wave increase in availability of amino acids (AAs) in plasma. We investigated the responses of quadriceps MPS to a ≈1.7-fold increase in plasma AA concentrations using an intravenous infusion of 162 mg (kg body weight)−1 h−1 of mixed AAs. MPS was estimated from D3-leucine labelling in protein after a primed, constant intravenous infusion of D3-ketoisocaproate, increased appropriately during AA infusion.
- 2Muscle was separated into myofibrillar, sarcoplasmic and mitochondrial fractions. MPS, both of mixed muscle and of fractions, was estimated during a basal period (2.5 h) and at 0.5-4 h intervals for 6 h of AA infusion.
- 3Rates of mixed MPS were not significantly different from basal (0.076 ± 0.008 % h−1) in the first 0.5 h of AA infusion but then rose rapidly to a peak after 2 h of ≈2.8 times the basal value. Thereafter, rates declined rapidly to the basal value. All muscle fractions showed a similar pattern.
- 4The results suggest that MPS responds rapidly to increased availability of AAs but is then inhibited, despite continued AA availability. These results suggest that the fed state accretion of muscle protein may be limited by a metabolic mechanism whenever the requirement for substrate for protein synthesis is exceeded.