Comparative hepatotoxicity of cholic acid, deoxycholic acid and lithocholic acid in the rat: in vivo and in vitro studies

Until now, the cytotoxicity of the bile acids was mostly seen as being inversely associated with their degree of lipophilicity. The present study aimed at comparing the hepatotoxicity of cholic acid (CA), deoxycholic acid (DCA) and lithocholic acid (LCA), which are respectively, tri-, di- and monohydroxylated bile acids. For in vivo studies, the bile acids have been given at the dose of 0.5% or 1 % in the diet of male Wistar rats for 2 weeks. The histological analysis of the liver, and the measurement of serum parameters of cytotoxicity and cholestasis (aminotransferases activity, bilirubin and total bile acids concentration), indicate that, among the bile acids tested, DCA is the most hepatotoxic, at both doses, while CA is the least hepatotoxic and cholestatic compound. Moreover, DCA is the only bile acid which, when given at the dose of 0.5%, induces lipid peroxidation in the liver, as evidenced by the measurement of thiobarbituric reactive substances in liver homogenates. The analysis of bile acids in liver homogenates by gas liquid chromatography revealed that feeding the animals with DCA results in its hepatic accumulation. Feeding rats with LCA or CA only slightly modifies the proportion of tri-, di- and monohydroxylated bile acids in the liver, as compared to controls. An in vitro experiment aimed at studying the hepatocellular lysis induced in vitro by the three bile acids by measuring the release of lactate dehydrogenase in the incubation medium of surviving hepatocytes in suspension. At a concentration of 1 mM, only DCA induces a significant cellular lysis, while at this concentration the lytic effects of CA and LCA are progressive and time-dependent. From this study, we gather that the hepatotoxicity of bile acids does not necessarily depend on their degree of hydroxylation. Our results are in accordance with some studies in rat hepatocarcinogenesis, showing a predominant initiating and promoting effects of DCA, as compared to LCA.