The secretion of bile requires the vectorial transport of organic and inorganic solutes from sinusoidal blood to the canalicular lumen.
Hydrostatic forces cannot account for biliary secretion, because secretory pressures within bile ducts exceed that of blood within the sinusoidal space. Instead, the process of bile formation requires active transport across the basolateral membrane, transcellular movement through a variety of mechanisms, and then active transport into the canalicular space between hepatocytes.
Separate hepatic and ductular transport mechanisms allow for rapid regulation of bile volume and composition required for changing physiologic needs.
The array of transport proteins localized to both poles of the hepatocyte have been characterized physiologically and during development.
See also
cellular secretion
References
Arrese M, Trauner M. Molecular aspects of bile formation and cholestasis. Trends Mol Med. 2003 Dec;9(12):558-64. PMID: 14659471
Arrese M, Ananthananarayanan M, Suchy FJ. Hepatobiliary transport: molecular mechanisms of development and cholestasis. Pediatr Res. 1998 Aug;44(2):141-7. PMID: 9702905