PMID: 8599317Apr 1, 1996Paper

Twenty-four-hour intravenous and oral tracer studies with L-[1-13C]phenylalanine and L-[3,3-2H2]tyrosine at a tyrosine-free, generous phenylalanine intake in adults

The American Journal of Clinical Nutrition
M SánchezV R Young

Abstract

The daily rates of whole-body phenylalanine oxidation and hydroxylation were determined in young men receiving [1-13C]phenylalanine and [2H2]tyrosine via primed, constant intravenous (n=3) or oral (n=5) infusion for 24 consecutive hours (12-h fast followed by 12-h fed period), and given a generous phenylalanine (100 mg.kg-1.d-1), tyrosine-free, but otherwise adequate L-amino acid-based diet for 6 d before the tracer study. Our hypothesis was that subjects would be in whole-body phenylalanine equilibrium. Estimates of the daily rates of phenylalanine oxidation (phe-ox) and hydroxylation (phe-OH) were significantly higher for the subjects receiving the oral compared with intravenous tracer (P<0.01 for both comparisons), with the estimates of phe-ox obtained with oral tracer during the 12-h fast period being close to those predicted from similar 24-h leucine kinetic studies. The precision of the agreement between the measured 24-h rates of phe-ox and phe-OH compared with the predicted daily rates by extrapolation from the last hour of the 12-h fast and fifth hour of the fed period was poor. From the 24-h data, daily phenylalanine balances were estimated to be positive for both the intravenous and oral tracer protocols, although it...Continue Reading

Citations

May 25, 1999·JPEN. Journal of Parenteral and Enteral Nutrition·Y M YuV R Young
Jan 10, 2006·The American Journal of Clinical Nutrition·Jean W-C HsuPaul B Pencharz
Feb 7, 2001·The American Journal of Clinical Nutrition·F J van SpronsenP G Smit
May 3, 2001·The American Journal of Clinical Nutrition·A V KurpadV R Young
May 2, 2003·The British Journal of Nutrition·Gerald E LobleyNgaire Dennison
Dec 24, 2010·Pediatric Research·Jean W HsuWilliam C Heird
Jan 29, 2000·The American Journal of Clinical Nutrition·C A RagusoV R Young
Oct 22, 2008·The Journal of Nutrition·Raffaella AntonioneGianni Biolo
Jun 10, 2006·The American Journal of Clinical Nutrition·Anura V KurpadVernon R Young
Apr 25, 2000·Metabolism: Clinical and Experimental·J M ThorpeP B Pencharz

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