Optimum conditions for the 13C-phenylalanine breath test.
We have conducted optimization studies to develop a superior 13C-phenylalanine breath test for the diagnosis of liver disease. First, we examined the optimum 13C-labeling position in phenylalanine for use in a breath test based on infrared spectroscopic detection of 13CO2 in exhaled air. L-[1-13C]Phenylalanine gave the best result. Next, a suitable dosage to give a short peak time (the time expressed in minutes at which 13CO2 excretion is maximal) after administration was determined. The 13CO2/12CO2 ratio in exhaled air after administration of 100 mg/body of L-[1-13C]phenylalanine peaked sharply at 15 min. We also examined the effect of food on the hepatic metabolism of L-[1-13C]phenylalanine. We found that a fasting period of over 7 h before the test resulted in a higher 13CO2 peak excretion. The peak appeared sooner than that in the 13C-phenacetin breath test and, therefore, the 13C-phenylalanine breath test appears preferable for the rapid evaluation of hepatic function.
Ishii
T
T
Department of Medicinal Chemistry, Meiji College of Pharmacy, Tokyo, Japan.
Takatori
K
K
Iida
K
K
Higuchi
T
T
Ohshima
A
A
Naruse
H
H
Kajiwara
M
M
D001944:Breath Tests / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis* / Q000378:metabolism*; D002247:Carbon Isotopes; D005215:Fasting / Q000378:metabolism; D005260:Female; D006801:Humans; D007536:Isomerism; D008107:Liver Diseases / Q000175:diagnosis / Q000378:metabolism; D008297:Male; D010615:Phenacetin / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism*; D013055:Spectrophotometry, Infrared; D013379:Substrate Specificity
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D010615:Phenacetin