| Abstract: | Abstract— Protein turnover in rat brain was measured over a period of 30 days by following the decay in specific radioactivity of acidic amino acids in proteins labelled by a single intraperitoneal injection of 14C]NaHCO3. Two major populations of brain proteins can be identified from the resultant non-linear decay curve—one with an average half-life of 4 days and another with an average half-life of 12 days. The half-lives of total brain, mitochondrial, microsomal and soluble proteins determined over a period of 5 days were 3.4, 5.8, 2.8, and 2.6 days, respectively. Turnover of these same brain subcellular fractions was also measured by continuous infusion of 14C]tyrosine. The estimated half-lives were in close agreement with those obtained from the 5 day measurement of radioactive decay following a pulse label of 14C]NaHCO3. |
