title: Comparison of turnover rates of proteins of the brain, liver and kidney in mouse in vivo following long term labeling.
abstract: Intraperitoneal injection of [14C]tyrosine suspension followed by subcutaneous implantation of a [14C]tyrosine pellet in mice produced a fairly constant specific activity of plasma free tyrosine for 5 days, and for 3-5 days in the tissue free amino acid pool. The specific activity of tyrosine in the tissue (brain, liver, and kidney) free amino acid pool was 75-90% of that in plasma. Incorporation of tyrosine into tissue proteins was followed for 5 days in brain; during this time 33% of tissue proteins were labeled. Incorporation for 68 h in liver and kidney showed labeling of over 70% of the protein of these tissues. These percentages assume a homogeneous tissue free tyrosine pool as the precursor. The rate of incorporation initially was 0.6, 2.8, and 2.0% per h in brain, liver, and kidney protein, respectively. These rates decreased in longer term experiments. The best fit to the incorporation curves was obtained by assuming the following average half-lives for tissue proteins: brain, two compartments, 5.7% with a half-life of 15 h, 94.3% with a half-life of 10 days; liver, a single compartment with a 26-h half-life; kidney, two compartments, 41% with an 18-h half-life, and 59% with a 63-h half-life.
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002250:Carbon Radioisotopes; D004355:Drug Stability; D006207:Half-Life; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008433:Mathematics; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009928:Organ Specificity; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D002250:Carbon Radioisotopes; D009419:Nerve Tissue Proteins; D011506:Proteins; D014443:Tyrosine