The estimation of protein fractional synthesis rate (FSR) is dependent on using the appropriate amino acid source to approximate the precursor pool specific radioactivity. Amino acids for protein synthesis can arise from extracellular sources (channeling), intracellular sources or protein degradation (recycling). The objective was to determine if whole body rates were equivalent to tissue rates of recycling and channeling. In order to estimate recycling and channeling, a dynamic, theoretical model of protein turnover for a non-growing 26g mouse was developed using 14C leucine in a flooding dose. The model consists of three protein pools turning over at fast (102umoles leu, t1/2 = 11.5hr), medium (212umoles leu, t1/2 = 16.6hr) or slow (536umoles leu, t1/2 = 71.5hr) rates and three free amino acids pools; leucyl-tRNA (0.0249umoles leu), intracellular leucine (5.72umoles leu) and extracellular leucine (1.69umoles leu). The model was adjusted to represent protein turnover in specific tissues: liver, muscle and intestine. Specific radioactivities from whole body and tissue experiments were fit to the whole body and tissue models, respectively, to estimate the rates of recycling and channeling. Data from 14C leucine flooding dose experiments in whole mice showed amino acids for protein synthesis were from extracellular sources. However, data from tissues indicated that in fast turnover tissues, amino acids for protein synthesis were primarily from recycling. Therefore current methods of estimating FSR include error associated with incorrectly estimating the precursor pool specific radioactivity.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology