Caffeine biotransformation in human hepatocyte lines derived from normal liver tissue.

Caffeine biotransformation was demonstrated in three novel human hepatocyte cell lines established from normal liver tissue and cultured continuously for 19 to 30 months. Caffeine and its metabolites were identified and quantified by high performance liquid chromatography. Without induction, caffeine was metabolized to the four primary metabolites [theobromine (37X), paraxanthine (17X), theophylline (13X), 1,3,7-trimethylurate (137U)]. Under these basal conditions 137U was the predominant metabolite. The actual pattern of metabolite production was a reproducible characteristic of each line. After induction with dibenz(a,h)anthracene, the formation of 17X was increased 4-17 fold. Induction with phenobarbital did not change the metabolic profile. These human hepatocyte lines can reproduce in vitro metabolism of caffeine observed in man in vivo.