Phenylalanine kinetics in healthy volunteers and liver cirrhotics: implications for the phenylalanine breath test.
Am J Physiol Endocrinol Metab
; 283(6): E1223-31, 2002 Dec.
Article
em En
| MEDLINE
| ID: mdl-12424105
ABSTRACT
Expired 13CO2 recovery from an oral l-[1-13C]phenylalanine ([13C]Phe) dose has been used to quantify liver function. This parameter, however, does not depend solely on liver function but also on total CO2 production, Phe turnover, and initial tracer distribution. Therefore, we evaluated the impact of these factors on breath test values. Nine ethyl-toxic cirrhotic patients and nine control subjects received intravenously 2 mg/kg of [13C]Phe, and breath and blood samples were collected over 4 h. CO2 production was measured by indirect calorimetry. The exhaled 13CO2 enrichments were analyzed by isotope ratio mass spectrometry and the [13C]Phe and l-[1-13C]tyrosine enrichments by gas chromatography-mass spectrometry. The cumulative 13CO2 recovery was significantly lower in cirrhotic patients (7 vs. 12%; P < 0.01), in part due to lower total CO2 production rates. Phe turnover in cirrhotic patients was significantly lower (33 vs. 44 micro mol. kg(-1). h(-1); P < 0.05). When these extrahepatic factors were considered in the calculation of the Phe oxidation rate, the intergroup differences were even more pronounced (3 vs. 7 micro mol. kg(-1). h(-1)) than those for 13CO2 recovery data. Also, the Phe-to-Tyr conversion rate, another indicator of Phe oxidation, was significantly reduced (0.7 vs. 3.0 micro mol. kg(-1). h(-1)).
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fenilalanina
/
Dióxido de Carbono
/
Cirrose Hepática Alcoólica
Tipo de estudo:
Clinical_trials
/
Prognostic_studies
Limite:
Adult
/
Aged
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
Am J Physiol Endocrinol Metab
Assunto da revista:
ENDOCRINOLOGIA
/
FISIOLOGIA
/
METABOLISMO
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Alemanha