title: Optimum conditions for the 13C-phenylalanine breath test.
abstract: 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.
authors.affiliation: Department of Medicinal Chemistry, Meiji College of Pharmacy, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishii
authors.forename: K
authors.initials: K
authors.lastname: Takatori
authors.forename: K
authors.initials: K
authors.lastname: Iida
authors.forename: T
authors.initials: T
authors.lastname: Higuchi
authors.forename: A
authors.initials: A
authors.lastname: Ohshima
authors.forename: H
authors.initials: H
authors.lastname: Naruse
authors.forename: M
authors.initials: M
authors.lastname: Kajiwara
mesh_terms: 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
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D010615:Phenacetin