Cytotoxic effect and uptake mechanism by isolated rat hepatocytes of lithocholate and its glucuronide and sulfate

Abstract The hepatotoxicity and uptake mechanism of lithocholate and its glucuronide and sulfate were studied using isolated rat hepatocytes. Cytotoxicity was in the order of litocholate > lithocholate-gluronide > lithocholate-sulfate; their 50% cytotoxic concentrations on hepatocytes were 50, 150 and 700 μM, respectively. Thus, glucuronidation as well as sulfation acted to detoxify lithocholate, not relating to the previously reported higher cholestatic effect of lithocholate-glucuronide than lithocholate. Lithocholate uptake was linear up to 50 μM, whereas the uptakes of lithocholate-glucuronide and sulfate were saturable with an apparent K m and V max of 32 μM and 6.4 nmol/min per 10 6 cells for lithocholate-glucuronide and 26 μM and 11.8 nmol/min per 10 6 cells for lithocholate-sulfate. Na + replacement by choline + had no effect on the uptake of lithocholate and lithocholate-glucuronide, whereas it slightly inhibited lithocholate-sulfate uptake. Lithocholate-glucuronide uptake was inhibited by lithocholate-sulfate and sulfobromophthalein, whereas lithocholate-glucuronide and sulfobromophthalein had no effect on lithocholate-sulfate uptake. These data indicate that hepatic lithocholate uptake is mediated by simple diffusion, and that hepatic uptake of lithocholate-glucuronide and sulfate is mainly mediated by a Na + -independent carrier.