title: Differential effects of cyclosporin A on transport of bile acids by rat hepatocytes: relationship to individual serum bile acid levels.
abstract: Cyclosporin A treatment has been reported to induce hepatotoxicity marked by a rise in total serum bile acid and total bilirubin. The mechanism of cyclosporin A-induced hepatotoxicity seems to be related to interference with hepatocellular transport of these substrates although this remains to be fully substantiated. The purpose of this study was to investigate whether the hepatocellular uptake of the different bile acids, in the presence of cyclosporin A, is consistent with the changes in their respective individual serum bile acid concentrations. High-performance liquid chromatography has been used to assay individual serum bile acids in cyclosporin A-treated rats at doses of 0.1, 1, and 10 mg/kg/day for 4 days. Control rats were treated with Cremophor (1 ml/kg/day). At the higher doses, cyclosporin A produced a significant increase in levels of cholic acid, taurocholic acid, chenodeoxycholic acid, and deoxycholic acid compared with controls. Serum glycocholate was unaffected even at the highest dose. Inhibition of initial rate of uptake and accumulation of [14C]cholic acid, [14C]chenodeoxycholic acid, and [14C]deoxycholic acid by isolated rat hepatocytes was consistent with the changes in their respective serum bile acids. Coincubation of rat hepatocytes with unlabeled cholic acid (100 microM), the major serum bile acid in cyclosporin A-treated rats, showed a further inhibitory effect on [14C]cholic acid and [14C]deoxycholic acid accumulation. The initial rate of uptake of [14C]glycocholate was also inhibited. However, accumulation of glycocholic acid did not show significant changes at the longer incubation times (2-30 min). In addition, coincubation of rat hepatocytes with unlabeled cholic acid (100 microM) plus cyclosporin A did not induce any inhibition of glycocholate accumulation. Together, these differences provide an explanation for the unchanged serum levels of glycocholate. In conclusion, the changes in individual serum bile acids in cyclosporin A-treated rats are consistent with the effect of this drug on their hepatocellular accumulation.
authors.affiliation: Toxicology Unit, National Institute of Occupational Health and Safety, University of Sydney, New South Wales, Australia.
authors.forename: S A
authors.initials: SA
authors.lastname: Azer
authors.forename: N H
authors.initials: NH
authors.lastname: Stacey
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D001692:Biological Transport / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D016572:Cyclosporine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007274:Injections, Intraperitoneal; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001647:Bile Acids and Salts; D016572:Cyclosporine