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Caffeine as a metabolic probe: Exploration of the enzyme‐inducing effect of cigarette smoking
Author(s) -
Kalow Werner,
Tang BingKou
Publication year - 1991
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1991.8
Subject(s) - caffeine , cotinine , nicotine , urine , enzyme , chemistry , cigarette smoking , population , enzyme inducer , metabolism , enzyme assay , medicine , urinary system , endocrinology , pharmacology , physiology , biochemistry , environmental health
It has been realized recently that the primary metabolism of caffeine in humans is catalyzed by P‐450IA2 and that the rate of caffeine metabolism can be estimated from a metabolic ratio in a single urine sample. A population of 178 students including 19 smokers were subjected to this caffeine test to establish their P‐450IA2 index. Both stated numbers of cigarettes smoked per day and urinary cotinine levels as a confirmatory measure correlated significantly with enzyme activity showing dose‐effect relationships (r = 0.62 and 0.89, respectively). Nevertheless, more nonsmokers than smokers had the highest enzyme indexes, suggesting that dietary elements or other factors may determine P‐450IA2 activities in populations. Because P‐450IA2 is a monooxygenase that may be confined to the liver, caffeine reveals directly the Ah‐receptor‐dependent enzyme induction only in the liver, but it may also be a signal of induction elsewhere. Clinical Pharmacology and Therapeutics (1991) 49 , 44–48; doi: 10.1038/clpt.1991.8