Document Detail


Metabolic conversion of L-[U-14C]phenylalanine to respiratory 14CO2 in healthy subjects, phenylketonuria heterozygotes and classic phenylketonurics.
MedLine Citation:
PMID:  3089645     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Ten healthy volunteers, 12 classic phenylketonuria (PKU) heterozygotes, and 5 classic phenylketonurics have been loaded orally with a mixture of 5 microCi of L-[U-14C]phenylalanine plus 25 mg/kg of L-[2H5]phenylalanine. For 3 h thereafter, carbon-14 activity in expired air and total carbon dioxide were measured continuously and the levels of L-phenylalanine and L-tyrosine in plasma were determined in six blood samples. After 3 h, 15.1 +/- 2.1% of the applied dose of radioactivity was recovered in the expired air of the healthy subjects, compared to 10.1 +/- 2.2% for PKU heterozygotes and 0.32 +/- 0.18% for classic phenylketonurics. The integrated activity expired provides a discrimination between normals and PKU heterozygotes with a classification error of about 13% compared to an error of about 9% based on the fasting L-phenylalanine over L-tyrosine ratio. A combination of these two parameters in a two-dimensional discriminatory analysis reduces the classification error to less than 1%. An intraindividual correlation between the absolute activity expired and the formation of L-[2H4]tyrosine formed is shown, confirming that ring hydroxylation of L-phenylalanine to L-tyrosine is mandatory in the catabolism of L-phenylalanine to carbon dioxide.
Authors:
W D Lehmann; R Fischer; H C Heinrich; P Clemens; R Grüttner
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Clinica chimica acta; international journal of clinical chemistry     Volume:  157     ISSN:  0009-8981     ISO Abbreviation:  Clin. Chim. Acta     Publication Date:  1986 Jun 
Date Detail:
Created Date:  1986-09-25     Completed Date:  1986-09-25     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  1302422     Medline TA:  Clin Chim Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  253-66     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Breath Tests
Carbon Dioxide / metabolism*
Carbon Radioisotopes / diagnostic use
Deuterium / diagnostic use
Heterozygote
Humans
Hydroxylation
Phenylalanine / metabolism*
Phenylketonurias / metabolism*
Tyrosine / metabolism
Chemical
Reg. No./Substance:
0/Carbon Radioisotopes; 124-38-9/Carbon Dioxide; 55520-40-6/Tyrosine; 63-91-2/Phenylalanine; 7782-39-0/Deuterium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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