[Bile secretion]

The canaliculus is the primary site for the formation of bile. Here, active secretion of bile acids creates an osmotic gradient between bile and blood, crossed passively by water and solutes. Numerous experimental data point to the existence of a canalicular bile fraction that is independent of the active transport of bile acids and related to active sodium secretion. The bile ducts are not mere conduits for the passage of bile, but can also change its volume and composition by means of both absorption and secretion. Nervous, vascular, hormonal and pharmacological factors serve to modify bile secretion. In most cases, however, their mechanism of action is virtually unknown.