title: Caffeine as a metabolic probe: validation of its use for acetylator phenotyping.
abstract: The use of two caffeine metabolite ratios for acetylator phenotyping was validated by demonstrating concordance with two sulfamethazine tests in 178 unrelated healthy subjects. The caffeine metabolites used for this purpose were 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X), and 1-methylurate (1U). The ratio AAMU/(AAMU + 1X + 1U), referred to as molar ratio or N-acetyltransferase, was compared with the ratio AAMU/1X. The results indicated that, for screening purposes, the acetylator phenotype can be determined by analysis of a 6-hour urine sample after a cup of coffee or strong tea or a can of caffeine-containing soft drink. The ratio AAMU/1X is the ratio of choice for the study of subjects in whom variability of xanthine oxidase can be neglected; use of the ratio AAMU/(AAMU + 1X + 1U) appears appropriate for special purposes. Gender, ethnic origin, habitual or moderate consumption of coffee, tea, soft drinks, or ethanol, or cigarette smoking have little if any effect on the caffeine tests for acetylator phenotyping.
authors.affiliation: Department of Pharmacology, University of Toronto, Ontario, Canada.
authors.forename: B K
authors.initials: BK
authors.lastname: Tang
authors.forename: D
authors.initials: D
authors.lastname: Kadar
authors.forename: L
authors.initials: L
authors.lastname: Qian
authors.forename: J
authors.initials: J
authors.lastname: Iriah
authors.forename: J
authors.initials: J
authors.lastname: Yip
authors.forename: W
authors.initials: W
authors.lastname: Kalow
mesh_terms: D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism*; D000328:Adult; D002110:Caffeine / Q000378:metabolism*; D006801:Humans; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000502:physiology*; D013418:Sulfamethazine / Q000097:blood / Q000652:urine; D013997:Time Factors; D014498:Uracil / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D014527:Uric Acid / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D014970:Xanthines / Q000097:blood / Q000652:urine
chemical_list: D014970:Xanthines; D014527:Uric Acid; C030530:1-methyluric acid; D002110:Caffeine; D013418:Sulfamethazine; D014498:Uracil; C053085:1-methylxanthine; D000123:Acetyltransferases; C054188:5-acetylamino-6-amino-3-methyluracil