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Abstract

Isolated hepatocyte cultures have become a frequently used model system for investigating drug metabolism. Although rat and hamster hepatocytes are frequently used for this purpose, metabolism in these species differs in many respects from human metabolism. A species with a metabolism more closely resembling that of humans might be more useful. Our in vivo experiments demonstrated that the metabolism of propranolol in the rabbit is more similar to that in humans than in rats or hamsters. We therefore examined the usefulness of rabbit parenchymal liver cells for studies of propranolol metabolism. A detailed method is presented for their preparation and culture, along with data on their viability, structure and protein synthesizing capability. One- or two-day-old hepatocyte cultures were exposed to 10 μmol/L 3H-propranolol from 30 min to hr; metabolites were identified by gas chromatography-mass spectrometry and quantitated by high-performance liquid chromatography. Propranolol metabolism was linear over 1 hr, with 15% of the substrate metabolized during this time. The cytochrome P-450 pathways, which result in ring oxidation and sidechain oxidation, were expressed in a reproducible fashion similar to that found in vivo in humans. The arylhydrocarbon hydroxylase inhibitor α-naphthoflavone (100 μmol/L) inhibited side-chain oxidation of propranolol by 90% without affecting ring oxidation. In contrast, cholorpromazine (100 μmol/L) was shown to inhibit ring oxidation of propranolol by 85% without affecting sidechain oxidation. Cimetidine (250 μmol/L) inhibited both pathways by about 50%. These observations suggest that rabbit hepatocyte metabolic pathways more closely resemble human cell metabolism and thus may be a more useful adjunct that rat or hamster hepatocytes in the study of drug-drug interactions when combined with in vivo studies in humans. (HEPATOLOGY 1990;11:394–400.)