title: In silico and in vitro modeling of hepatocyte drug transport processes: importance of ABCC2 expression levels in the disposition of carboxydichlorofluroscein.
abstract: The impact of transport proteins in the disposition of chemicals is becoming increasingly evident. Alteration in disposition can cause altered pharmacokinetic and pharmacodynamic parameters, potentially leading to reduced efficacy or overt toxicity. We have developed a quantitative in silico model, based upon literature and experimentally derived data, to model the disposition of carboxydichlorofluroscein (CDF), a substrate for the SLCO1A/B and ABCC subfamilies of transporters. Kinetic parameters generated by the in silico model closely match both literature and experimentally derived kinetic values, allowing this model to be used for the examination of transporter action in primary rat hepatocytes. In particular, we show that the in silico model is suited to the rapid, accurate determination of K(i) values, using 3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid (MK571) as a prototypical pan-ABCC inhibitor. In vitro-derived data are often used to predict in vivo response, and we have examined how differences in protein expression levels between these systems may affect chemical disposition. We show that ABCC2 and ABCC3 are overexpressed in sandwich culture hepatocytes by 3.5- and 2.3-fold, respectively, at the protein level. Correction for this in markedly different disposition of CDF, with the area under the concentration versus time curve and C(max) of intracellular CDF increasing by 365 and 160%, respectively. Finally, using kinetic simulations we show that ABCC2 represents a fragile node within this pathway, with alterations in ABCC2 having the most prominent effects on both the K(m) and V(max) through the pathway. This is the first demonstration of the utility of modeling approaches to estimate the impact of drug transport processes on chemical disposition.
authors.affiliation: Centre for Toxicology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK.
authors.forename: Katharine
authors.initials: K
authors.lastname: Howe
authors.forename: G Gordon
authors.initials: GG
authors.lastname: Gibson
authors.forename: Tanya
authors.initials: T
authors.lastname: Coleman
authors.forename: Nick
authors.initials: N
authors.lastname: Plant
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D005452:Fluoresceins / Q000032:analysis / Q000378:metabolism*; D015870:Gene Expression; D022781:Hepatocytes / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D004364:Pharmaceutical Preparations / Q000378:metabolism; D010829:Physiological Phenomena; D051381:Rats
chemical_list: D018528:ATP-Binding Cassette Transporters; C423013:Abcc2 protein, rat; D005452:Fluoresceins; D004364:Pharmaceutical Preparations; C053897:5(6)-carboxy-2',7'-dichlorofluorescein