Effect of exercise on protein turnover in man.
1. We have investigated the effects of moderate long-term exercise on protein turnover in fed man by measuring the extent of whole-body nitrogen production, the labelling of urinary ammonia from ingested [15N]glycine and plasma, muscle and urine free amino acid concentrations. 2. Judged both from nitrogen production, and from the extent of 13CO2 production from ingested L-[1-13C]leucine, exercise causes a substantial rise in amino acid catabolism. 3. Amino acids catabolized during exercise appear to become available through a fall in whole-body protein synthesis and a rise in whole-body protein breakdown. After exercise, protein balance becomes positive through a rise in the rate of whole-body synthesis in excess of breakdown. 4. Studies of free 3-methylhistidine in muscle, plasma and urine samples suggest that exercise decreases the fractional rate of myofibrillar protein breakdown, in contrast with the apparent rise in whole-body breakdown.
D000328:Adult; D000596:Amino Acids / Q000378:metabolism; D000641:Ammonia / Q000652:urine; D003404:Creatinine / Q000032:analysis; D005998:Glycine / Q000097:blood; D006801:Humans; D008297:Male; D008762:Methylhistidines / Q000096:biosynthesis; D008875:Middle Aged; D009132:Muscles / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D009584:Nitrogen / Q000096:biosynthesis; D005082:Physical Exertion; D011506:Proteins / Q000378:metabolism*; D014508:Urea / Q000032:analysis
D000596:Amino Acids; D008762:Methylhistidines; D011506:Proteins; D000641:Ammonia; D014508:Urea; D003404:Creatinine; C028118:3-methylhistidine; D009584:Nitrogen; D005998:Glycine