Lithocholate cholestasis—Sulfated glycolithocholate-induced intrahepatic cholestasis in rats

Abstract

The intrahepatic cholestasis induced by lithocholic acid and its conjugates is characterized by specific morphological and biochemical changes in the bile canalicular membrane. Although sulfation of lithocholates has been suggested as an important detoxification mechanism, there is as yet little experimental evidence to support this contention. A bile fistula was created in male Wistar rats and 2 h later, they were given i.v. (24 μmoles/100 g body wt) one of the following: lithocholic acid sulfate, its taurine or glycine conjugate. Taurolithocholic acid sulfate-injected animals showed no change in bile flow monitored every 15 min over a 2-h period when compared to controls who received a bile acid-free solution of 7.5% albumin in 0.45% NaCl. The response to lithocholic acid sulfate was variable and characterized by a 20% decrease in bile flow limited to the first 30 min. In contrast, glycolithocholic acid sulfate reduced bile flow by more than 60% in the first 30 min in a dose-dependent manner. Thereafter, bile flow gradually returned to 70% of the control level. Lithocholic acid sulfate was mainly excreted as a taurine conjugate. Taurolithocholic acid sulfate rapidly appeared in bile in contrast to the delayed appearance of glycolithocholic acid sulfate. Lithocholic acid sulfate and taurolithocholic acid sulfate did not lead to any electron microscopy changes in hepatocytes. However, glycolithocholic acid sulfate induced the formation of single membrane bound cytoplasmic vacuoles containing material of low electron density which were evident as early as 10 min after injection. The percent of hepatocytes with cytoplasmic vacuoles and the percent volume density of vacuoles reached its maximum at 60 min after injection. At 2 h, these values did not differ significantly from controls. The bile canaliculi appeared normal and contained canalicular microvilli. These data suggest that sulfated lithocholic acid conjugated with glycine is cholestatic in rats and that the mechanism may differ from the cholestasis induced by lithocholic acid.