title: Impact of separating amino acids between plasma, extracellular and intracellular compartments on estimating protein synthesis in rodents.
abstract: Three models representing different separations of amino acid sources were used to simulate experimental specific radioactivity data and to predict protein fractional synthesis rate (FSR). Data were from a pulse dose of 14C-U Leu given to a non-growing 20-g mouse and a flooding dose of 3H Phe given to a non-growing 200 g rat. Protein synthesis rates estimated using the combined extracellular and intracellular (Ec + Ic) source pool and extracellular and plasma (Ec + Pls) source pool mouse models were 78 and 120% d(-1) in liver, 14 and 16% d(-1) in brain and 15 and 14% d(-1) in muscle. Predicted protein synthesis rates using the Ec + Ic, Ec + Ic + Tr (combined extracellular, intracellular and aminoacyl tRNA source pool) and Ec + Pls rat models were 57, 3.4 and 57% d(-1) in gastrocnemius, 58, 71 and 62% d(-1) in gut, 8.3, 8.4 and 7.9% d(-1) in heart, 32, 23 and 25% d(-1) in kidney, 160, 90 and 80% d(-1) in liver, 57, 5.5 and 57% d(-1) in soleus and 56, 3.4 and 57% d(-1) in tibialis. The Ec + Ic + Tr model underestimated protein synthesis rates in mouse tissues (5.0, 27 and 2.5% d(-1) for brain, liver and muscle) and rat muscles (3.4, 5.5 and 3.4% d(-1) for gastrocnemius, soleus and tibialis). The Ec + Pls model predicted the mouse pulse dose data best and the Ec + Ic model predicted the rat flooding dose data best. Model predictions of FSR imply that identification and separation of the source specific radioactivity is critical to accurately estimate FSR.
authors.affiliation: Animal Science Department, University of California at Davis, 95616, USA. HAJohnson@UCDavis.edu
authors.forename: H A
authors.initials: HA
authors.lastname: Johnson
authors.forename: R L
authors.initials: RL
authors.lastname: Baldwin
authors.forename: K C
authors.initials: KC
authors.lastname: Klasing
authors.forename: C C
authors.initials: CC
authors.lastname: Calvert
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000737:chemistry* / Q000302:isolation & purification*; D000818:Animals; D001921:Brain / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000737:chemistry; D051379:Mice; D008954:Models, Biological; D009132:Muscles / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry; D014176:Protein Biosynthesis; D011506:Proteins / Q000737:chemistry; D051381:Rats; D012984:Software; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D000596:Amino Acids; D011506:Proteins; D010649:Phenylalanine; D007930:Leucine