Abstract
The origin of the amino acids in the precursor pool for hepatic protein synthesis has been studied by following the distribution of administered [3H]Asp and [3H]Val to the tRNA-charged, the extracellular (EC) and the intracellular (IC) amino acid pools of rat liver under two physiological states (fed and starved). Our results indicated that both the EC and IC amino acids contributed to the precursor pool for hepatic protein synthesis. Asp was mainly derived from the IC pool for protein synthesis, but in Val, the contribution of the IC and EC pools was not differentiated in fed rats, because the specific radioactivities of the three Val pools were very close. In starved rats, the difference in the contributions of IC and EC Val was relatively small. The difference in the specific radioactivities between tRNA-charged and hepatic EC or IC free amino acids depended on the kind of amino acids and the physiological states of the animals.
