Musle protein breakdown rates in humans based on Ntau-methylhistidine (3-methylhistidine) content of mixed proteins in skeletal muscle and urinary output of Ntau-methylhistidine.
Samples of psoas muscle from nine infants (aged 1 day to 14 mo) and of several skeletal muscles from seven adult males (age 19-74 yr) were analyzed for content of protein-bound Ntau-methylhistidine (3-methylhistidine; 3-Mehis). The mean content of 3-Mehis (expressed as mumoles/g mixed protein) was 3.2 (range 2.4-3.7) in infants and 4.2 (range 3.7-4.6) in adults. The daily urinary excretion of 3-Mehis was measured in four young adult males receiving an egg-protein, flesh-free diet. Mean excretion of 3-Mehis was 211 (range 167-252) mumoles/day. From these two sets of data the mean rate of muscle protein breakdown in adult males was estimated to be 50 g/day, or 0.7 +/- 0.1 g/kg body weight/day. These results are compared with reported values for the 3-Mehis content of mixed proteins in muscle of various species, and with published estimates, computed by other techniques, of the rate of muscle protein breakdown in human subjects.
D000328:Adult; D000368:Aged; D004044:Dietary Proteins; D004531:Eggs; D005260:Female; D006639:Histidine / Q000031:analogs & derivatives*; D006801:Humans; D007223:Infant; D008297:Male; D008460:Meat; D008762:Methylhistidines / Q000032:analysis* / Q000652:urine; D008875:Middle Aged; D009124:Muscle Proteins / Q000032:analysis / Q000378:metabolism*; D009132:Muscles / Q000032:analysis* / Q000378:metabolism; D011485:Protein Binding
D004044:Dietary Proteins; D008762:Methylhistidines; D009124:Muscle Proteins; D006639:Histidine