L-[1-C-13] PHENYLALANINE OXIDATION AS A MEASURE OF HEPATOCYTE FUNCTIONAL-CAPACITY IN END-STAGE LIVER-DISEASE

BACKGROUND: Liver disease is associated with impaired metabolism of th ese amino acids phenylalanine and tyrosine. Decreased metabolism of th ese amino acids leads to abnormal plasma elevations and impaired clear ance rates. We have developed a noninvasive breath test that measures hepatic cytosolic enzyme activity. METHODS: The rate of hepatic phenyl alanine metabolism was quantitatively calculated from the appearance o f (CO2)-C-13 in the breath using the nonradioactive tracer L-[1-C-13]p henylalanine. RESULTS: Normal controls (n = 47) oxidized phenylalanine more than twice that of end-stage fiver disease patients (n = 117). S ignificant differences in the percent of phenylalanine oxidized per ho ur (mean +/- SEM) were found between controls (7.08% +/- 0.33%, 95% Cl : 6.42%-7.74%) and Child Pugh classification patients, class A (4.96% +/- 0.69%, 95% Cl: 3.50%-6.42%), class B (2.88% +/- 0.13, 95% Cl: 2.39 %-3.38%) and class C (1.75% +/- 0.13, 95% Cl: 1.50%-2.01%). The phenyl alanine breath test score significantly correlated with albumin levels , prothrombin time and total bilirubin. CONCLUSION: We have demonstrat ed that phenylalanine oxidation is significantly decreased with end-st age liver disease and is correlated with the best clinical measures of fiver disease. (C) 1997 by Excerpta Medica, Inc.