Influence of Verapamil and Cyclosporin A on bile acid metabolism and transport in rat liver slices.
Verapamil (V) is a specific inhibitor of the P-glycoprotein (mdr1) in the hepatocyte canalicular membrane. Cyclosporin A (CsA) as an essential immunosuppressive drug has potentially cholestatic adverse effects on the liver, but increases the expression of mdr1. In precision-cut liver slices from 34- to 40-day-old male Wistar rats 26 individual free and conjugated bile acids (BAs) as markers of hepatic transport and synthesis function were analysed after 4 h incubation with V (100 microM) or CsA (5 microM) in Krebs-Henseleit buffer. Some slices were loaded with cholic acid (CA 5 microM) or tauro-ursodeoxycholic acid (T-UDCA 5 microM) to investigate the V and CsA effects under conditions of BA supplementation. BAs were determined in tissue and medium by HPLC with postcolumn derivatisation and fluorescence detection. V and CsA, influencing different targets in BA transport, enhanced slice concentrations of T- and glyco- (G-) conjugated CA only when exogenous CA was given additionally. This BA accumulation in tissue is more reflected at decreased medium concentrations of these BAs after V and CsA incubations. Both V and CsA also inhibited CA uptake into the slices. The acidic chenodeoxycholic acid (CDCA) synthesis pathway is disturbed: T- and G-CDCA concentrations are diminished in slices and medium after V and CsA incubations. T-UDCA plus V or CsA enhanced not only its own slice concentration but also the concentration of the trihydroxylated tauro-muricholic acid (T-beta-MCA), reflecting the conversion of the accumulated dihydroxylated T-UDCA into the T-beta-MCA. The similar effects of V and CsA on BA transport and metabolism can be explained by mdr1 mediated disturbances of cellular ATP transport rather than by inhibition of individual BA transporters.
Barth
Astrid
A
Institute of Pharmacology and Toxicology, Friedrich Schiller University Jena, D-07740 Jena, Germany. Astrid.Barth@mti.uni-jena.de
Braun
Jerome
J
Müller
Dieter
D
D000818:Animals; D021461:Animals, Outbred Strains; D001692:Biological Transport / Q000187:drug effects; D002793:Cholic Acids / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D016572:Cyclosporine / Q000494:pharmacology*; D004338:Drug Combinations; D066298:In Vitro Techniques; D008099:Liver / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013655:Taurochenodeoxycholic Acid / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology*
D002793:Cholic Acids; D004338:Drug Combinations; D013655:Taurochenodeoxycholic Acid; D016572:Cyclosporine; D014700:Verapamil