Kinetics of caffeine metabolism in control and 3-methylcholanthrene induced rat liver microsomes.

The kinetics of formation of primary metabolites of caffeine (paraxanthine, theophylline, theobromine and 1,3,7-trimethyluric acid) was studied in control (CO) and 3-methylcholanthrene-induced (MC) rat liver microsomes. Vmax was similar but Km was 16 times lower for total caffeine metabolism in CO and MC microsomes, respectively. Similar behavior was observed in the formation of each metabolite. Single metabolites showed different degrees of induction at non-saturating concentrations of caffeine. Kinetics was non-linear in CO microsomes.