Stimulation of protein synthesis in pig skeletal muscle by infusion of amino acids during constant insulin availability.
Incorporation of L-[1-13C]leucine into muscle protein and leg exchange of L-[15N]phenylalanine were used to assess the effects over 240 min of amino acid supply on leg protein turnover in anesthetized, overnight-fasted (Landrace x Great White) female pigs. In all pigs, plasma insulin and glucagon stability was ensured by infusion of somatostatin (8 micrograms.kg-1.h-1), insulin (6 mU.kg-1.h-1), and glucagon (72 ng.kg-1.h-1). Mixed amino acid infusion (260 mg.kg-1.h-1) caused a 2- to 2.5-fold elevation of arterial plasma phenylalanine and leucine; in a control group (no amino acid infusion), an increase in phenylalanine and leucine concentration was observed as a result of the hormone clamp. Plasma insulin and glucagon concentrations were steady and not significantly different between control and amino acid-infused groups during the final 240 min, but plasma glucose fell (P less than 0.05) in both groups (4.57 +/- 0.17 to 3.15 +/- 0.73 mM). Muscle protein synthetic rate (estimated from the change in L-[1-13C]leucine incorporation compared with labeling of [13C]leucyl-tRNA) was greater in amino acid-infused (0.076%/h) than in control (0.053%/h) pigs. In the control group, leg amino acid balance was negative (Phe alone, -10.2 +/- 9.4 nmol Phe.100 g-1.min-1; total amino acids, -0.27 +/- 1.04 micrograms amino N.100 g-1.min-1), but during amino acid infusion, balance was positive (Phe alone, +33.6 +/- 8.8 nmol Phe.100 g-1.min-1; total amino acids, +58.2 +/- 4.9 micrograms amino N.100 g-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)
Watt
P W
PW
Department of Anatomy and Physiology, University of Dundee, Scotland.
Corbett
M E
ME
Rennie
M J
MJ
D000596:Amino Acids / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001682:Biological Availability; D001786:Blood Glucose / Q000032:analysis; D005260:Female; D005934:Glucagon / Q000097:blood; D006614:Hindlimb / Q000098:blood supply; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis*; D009132:Muscles / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D012039:Regional Blood Flow; D013552:Swine
D000596:Amino Acids; D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins; D010649:Phenylalanine; D005934:Glucagon; D007930:Leucine