title: Dose-dependent inhibition of transporter-mediated hepatic uptake and biliary excretion of methotrexate by cyclosporine A in an isolated perfused rat liver model.
abstract: Methotrexate (MTX) and cyclosporine (CyA) are coadministered in a number of diseases. In this study, the effects of CyA on the hepatobiliary disposition of MTX were investigated in an isolated perfused rat liver model. A bolus 5-mg dose of MTX was added to a recirculating perfusate in the absence or presence of a relatively low (0.5 mg) or high (2.5 mg) dose of CyA or vehicle pretreatment, and perfusate, bile, and terminal liver samples were collected for analysis by high-performance liquid chromatography (HPLC). In control and vehicle groups, MTX showed a low hepatic extraction ratio (∼0.1) and was almost completely eliminated by excretion into the bile. The low-dose CyA significantly reduced (60%) the hepatic extraction ratio and clearance of MTX, without affecting the bile/liver concentration ratio, suggesting inhibition of sinusoidal uptake of MTX only. In contrast, the high-dose CyA significantly reduced both hepatic uptake and Mrp2-mediated biliary excretion of MTX. Isolated rat hepatocyte uptake studies showed significant inhibition of [(3)H]MTX uptake in the presence of CyA. It is concluded that CyA significantly alters the hepatobiliary disposition of MTX by inhibiting its sinusoidal uptake and/or biliary transport, potentially reducing enterohepatic recirculation of the drug in vivo.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 Coulter, Amarillo, Texas 79106, USA.
authors.forename: Ridhi
authors.initials: R
authors.lastname: Parasrampuria
authors.forename: Reza
authors.initials: R
authors.lastname: Mehvar
mesh_terms: D000818:Animals; D001646:Bile / Q000737:chemistry; D001659:Biliary Tract / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D050217:Metabolic Detoxication, Phase II; D008727:Methotrexate / Q000378:metabolism* / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D026901:Membrane Transport Proteins; D016572:Cyclosporine; D008727:Methotrexate