TY - JOUR
T1 - Protein synthesis rates in human muscles
T2 - Neither anatomical location nor fibre-type composition are major determinants
AU - Mittendorfer, B.
AU - Andersen, J. L.
AU - Plomgaard, P.
AU - Saltin, B.
AU - Babraj, J. A.
AU - Smith, K.
AU - Rennie, M. J.
PY - 2005/2/15
Y1 - 2005/2/15
N2 - In many animals the rate of protein synthesis is higher in slow-twitch, oxidative than fast-twitch, glycolytic muscles. To discover if muscles in the human body also show such differences, we measured [13C]leucine incorporation into proteins of anatomically distinct muscles of markedly different fibre-type composition (vastus lateralis, triceps, soleus) after an overnight fast and during infusion of a mixed amino acid solution (75 mg amino acids kg-1 h-1) in nine healthy, young men. Type-1 fibres contributed 83 ± 4% (mean ± S.E.M.) of total fibres in soleus, 59 ± 3% in vastus lateralis and 22 ± 2% in triceps. The basal myofibrillar and sarcoplasmic protein fractional synthetic rates (FSR, % h-1) were 0.034 ± 0.001 and 0.064 ± 0.001 (soleus), 0.031 ± 0.001 and 0.060 ± 0.001 (vastus), and 0.027 ± 0.001 and 0.055 ± 0.001 (triceps). During amino acid infusion, myofibrillar protein FSR increased to 3-fold, and sarcoplasmic to 2-fold basal values (P < 0.001). The differences between muscles, although significant statistically (triceps versus soleus and vastus lateralis, P < 0.05), were within ∼15%, biologically probably insignificant. The rates of collagen synthesis were not affected by amino acid infusion and varied by < 5% between muscles and experimental conditions.
AB - In many animals the rate of protein synthesis is higher in slow-twitch, oxidative than fast-twitch, glycolytic muscles. To discover if muscles in the human body also show such differences, we measured [13C]leucine incorporation into proteins of anatomically distinct muscles of markedly different fibre-type composition (vastus lateralis, triceps, soleus) after an overnight fast and during infusion of a mixed amino acid solution (75 mg amino acids kg-1 h-1) in nine healthy, young men. Type-1 fibres contributed 83 ± 4% (mean ± S.E.M.) of total fibres in soleus, 59 ± 3% in vastus lateralis and 22 ± 2% in triceps. The basal myofibrillar and sarcoplasmic protein fractional synthetic rates (FSR, % h-1) were 0.034 ± 0.001 and 0.064 ± 0.001 (soleus), 0.031 ± 0.001 and 0.060 ± 0.001 (vastus), and 0.027 ± 0.001 and 0.055 ± 0.001 (triceps). During amino acid infusion, myofibrillar protein FSR increased to 3-fold, and sarcoplasmic to 2-fold basal values (P < 0.001). The differences between muscles, although significant statistically (triceps versus soleus and vastus lateralis, P < 0.05), were within ∼15%, biologically probably insignificant. The rates of collagen synthesis were not affected by amino acid infusion and varied by < 5% between muscles and experimental conditions.
UR - http://www.scopus.com/inward/record.url?scp=14844318032&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2004.077180
DO - 10.1113/jphysiol.2004.077180
M3 - Article
C2 - 15611031
AN - SCOPUS:14844318032
SN - 0022-3751
VL - 563
SP - 203
EP - 211
JO - Journal of Physiology
JF - Journal of Physiology
IS - 1
ER -