The paracellular pathway and bile formation.

Choleretic infusions of taurocholate (40 μ moles for one hour) result in a significant increase in the number of lateral cell surface invaginations observed by scanning electron microscopy adjacent to the junctional complex of bile canaliculi in rat liver. Transmission electron microscopy indicates that these invaginations resemble "blisters" induced by osmotic gradients across epithelial tissues, a morphologic change which correlates with increases in ionic and hydraulic conductivity of the paracellular "shunt" pathway in such tissue. Since taurocholate infusions result in localization of ionic lanthanum chloride within hepatocyte junctional complexes, bile acids may also stimulate the movement of fluid and electrolytes across paracellular pathways during the process of bile formation.