Do intracellular organelles have any role in transport of bile acids by hepatocytes?

The mechanisms of intracellular transport of bile acids by the hepatocyte and the regulation of their canalicular secretion are still incompletely understood. In this article, the evidence for a role of intracellular vesicles in bile acid transport by the hepatocyte is reviewed. Electron microscopic, immunoperoxidase, immunofluorescent and autoradiographic observations have shown a localization of bile acids on intracellular vesicles, on the Golgi apparatus and endoplasmic reticulum. Microtubule inhibitors, such as colchicine and vinblastine, have been shown to inhibit bile acid transport into bile. These observations are consistent with the hypothesis that bile acid canalicular transporters are recycled from an intracellular vesicular pool to the canalicular membrane. This membrane trafficking is a microtubule-dependent process. Confirmation of this hypothesis will require direct demonstration of the transporters on intracellular vesicles and movement of these vesicles to the canalicular membrane under appropriate conditions.