Abstract
1. 1. The distribution of acid-soluble and acid-insoluble radioactivity in homogenates of rat liver and the distribution of acid-insoluble radioactivity in various cell fractions of homogenates have been studied in a balance-sheet manner at various time points following a single intraperitoneal injection of labeled orotic acid. 2. 2. Equilibrium between the amounts of radioactivity in the acid-soluble pool and in the pool of nuclear RNA reached a ratio of about 8:1 by 3 h and remained constant from that time on. By the same criterion, equilibrium between the amounts of radioactivity in the acid-soluble pool and in the total acid-insoluble pool was reached after 36 h, with approx, 20% of the total radioactivity in the acid-soluble fraction. 3. 3. The apparent half lives of RNA in the nuclei, total ribosome fraction and nonsedimentable RNA were found to be 120 ± 13, 99 ± 11 and 90 ± 11 h, respectively. Similar half lives were calculated from the decay of the total radioactivity in these fractions per mg DNA. The total radioactivity per mg DNA in the acid-soluble fraction decayed with an apparent half life of 104 h. 4. 4. Evidence for reutilization of nucleotides has been obtained.
Published Version
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