A comparison of methods for the measurement of protein turnover in vivo.
Steady-state rates of turnover of two single proteins were measured in vivo by two independent methods. The fractional rate of synthesis of liver ornithine aminotransferase, measured by a continuous infusion of L-[2,6-3H]tyrosine, was 0.42 day-1, whereas in the same animals the fractional rate of degradation measured by loss of radioactivity from amino acids labelled via [14C]bicarbonate was 0.40 day-1. The agreement between methods confirms the reliability of each method for the study of hepatic protein turnover. In contrast, [14C]bicarbonate-labelled amino acids are extensively reutilized in muscle, and are therefore unsuitable for measuring rates of muscle protein breakdown.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002250:Carbon Radioisotopes; D005634:Fructose-Bisphosphate Aldolase / Q000096:biosynthesis / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D008722:Methods; D009132:Muscles / Q000201:enzymology; D009953:Ornithine-Oxo-Acid Transaminase / Q000096:biosynthesis / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D014316:Tritium; D014443:Tyrosine / Q000378:metabolism
D001639:Bicarbonates; D002250:Carbon Radioisotopes; D011506:Proteins; D014316:Tritium; D014443:Tyrosine; D009953:Ornithine-Oxo-Acid Transaminase; D005634:Fructose-Bisphosphate Aldolase