Human Hepatocytes in Primary Culture: The Choice to Investigate Drug Metabolism in Man
Different types of hepatic tissue, including whole or split livers from organ donors or waste liver from therapeutic liver resections, are used to prepare human hepatocyte cultures. Characteristics of liver samples from different origins (gender, age, healthy / pathological status, xenobiotic treatment) as sources of human hepatocytes are key factors which notably determine viability and functionality of hepatocytes. The characterisation of the CYP system can be assessed in terms of activity (using specific substrates / inhibitors), protein (antibody analysis) and molecular biology-based mRNA amplification techniques (PCR technology and DNA microarrays). It could reasonably be considered that human hepatocytes reflect the heterogeneity of CYP expression in human liver and is a suitable model for drug metabolism studies. Several key issues need to be addressed at the early stages of drug development to better select drug candidates (metabolic profile and rate, identification of CYPs involved, drug-drug interactions due to enzyme induction / inhibition). The metabolic stability and metabolite profile of new chemicals can be easily investigated by incubating the drugs with fully competent metabolic models like hepatocyte suspensions or 24 h-cultured hepatocytes. CYP inhibitory effects are usually screened in recombinant CYP enzymes or microsomes, however, the actual concentration of substrate and inhibitor available to the CYP enzyme depends on processes missing in subcellular models (transport mechanisms, cytosolic enzymes, binding to intracellular proteins). Since intact cells more closely reflect the environment to which drugs are exposed in the liver, cultured hepatocytes constitute a more predictive model for drug-drug interactions. Screening of CYP inducers cannot be done in microsomes as it requires a cellular system fully capable of expressing CYP genes. Primary hepatocytes are still the unique in vitro model for global examination of inductive potential of drugs (monitored as increases in mRNA content or activity).
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Document Type: Review Article
Affiliations: Centro de Investigacion, Hospital La Fe, Avda de Campanar 21, 46009-Valencia (Spain).
Publication date: October 1, 2004
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- Current Drug Metabolism aims to cover all the latest and outstanding developments in drug metabolism and disposition. The journal serves as an international forum for the publication of timely reviews in drug metabolism. Current Drug Metabolism is an essential journal for academic, clinical, government and pharmaceutical scientists who wish to be kept informed and up-to-date with the latest and most important developments. The journal covers the following areas:
In vitro systems including CYP-450; enzyme induction and inhibition; drug-drug interactions and enzyme kinetics; pharmacokinetics, toxicokinetics, species scaling and extrapolations; P-glycoprotein and transport carriers; target organ toxicity and interindividual variability; drug metabolism and disposition studies; extrahepatic metabolism; phase I and phase II metabolism; recent developments for the identification of drug metabolites and adducts.
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