{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2023,4,28]],"date-time":"2023-04-28T04:44:27Z","timestamp":1682657067417},"reference-count":25,"publisher":"American Physiological Society","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Endocrinology and Metabolism"],"published-print":{"date-parts":[[2002,12,1]]},"abstract":" Expired 13<\/jats:sup>CO2<\/jats:sub>recovery from an oral l-[1-13<\/jats:sup>C]phenylalanine ([13<\/jats:sup>C]Phe) dose has been used to quantify liver function. This parameter, however, does not depend solely on liver function but also on total CO2<\/jats:sub> 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 [13<\/jats:sup>C]Phe, and breath and blood samples were collected over 4 h. CO2<\/jats:sub> production was measured by indirect calorimetry. The exhaled 13<\/jats:sup>CO2<\/jats:sub> enrichments were analyzed by isotope ratio mass spectrometry and the [13<\/jats:sup>C]Phe and l-[1-13<\/jats:sup>C]tyrosine enrichments by gas chromatography-mass spectrometry. The cumulative13<\/jats:sup>CO2<\/jats:sub> recovery was significantly lower in cirrhotic patients (7 vs. 12%; P < 0.01), in part due to lower total CO2<\/jats:sub> production rates. Phe turnover in cirrhotic patients was significantly lower (33 vs. 44 \u03bcmol \u00b7 kg\u22121<\/jats:sup> \u00b7 h\u22121<\/jats:sup>; 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 \u03bcmol \u00b7 kg\u22121<\/jats:sup> \u00b7 h\u22121<\/jats:sup>) than those for 13<\/jats:sup>CO2<\/jats:sub> recovery data. Also, the Phe-to-Tyr conversion rate, another indicator of Phe oxidation, was significantly reduced (0.7 vs. 3.0 \u03bcmol \u00b7 kg\u22121<\/jats:sup> \u00b7 h\u22121<\/jats:sup>). <\/jats:p>","DOI":"10.1152\/ajpendo.0311.2001","type":"journal-article","created":{"date-parts":[[2015,2,27]],"date-time":"2015-02-27T20:14:36Z","timestamp":1425068076000},"page":"E1223-E1231","source":"Crossref","is-referenced-by-count":15,"title":["Phenylalanine kinetics in healthy volunteers and liver cirrhotics: implications for the phenylalanine breath test"],"prefix":"10.1152","volume":"283","author":[{"given":"I.","family":"Tugtekin","sequence":"first","affiliation":[{"name":"Sektion An\u00e4sthesiologische Pathophysiologie und Verfahrensentwicklung, Universit\u00e4tsklinik f\u00fcr An\u00e4sthesiologie Ulm, und"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"U.","family":"Wachter","sequence":"additional","affiliation":[{"name":"Sektion An\u00e4sthesiologische Pathophysiologie und Verfahrensentwicklung, Universit\u00e4tsklinik f\u00fcr An\u00e4sthesiologie Ulm, und"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"E.","family":"Barth","sequence":"additional","affiliation":[{"name":"Sektion An\u00e4sthesiologische Pathophysiologie und Verfahrensentwicklung, Universit\u00e4tsklinik f\u00fcr An\u00e4sthesiologie Ulm, und"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H.","family":"Weidenbach","sequence":"additional","affiliation":[{"name":"Abteilung Innere Medizin I, Medizinische Universit\u00e4tsklinik und Poliklinik Ulm, 89070 Ulm, Germany; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"D. 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