Bile canaliculus

Curtis LR. 1988. Chlordecone is a potent in vitro inhibitor of oligomycin-insensitive magnesium-ATPase of rat bile canaliculi-enriched fraction. J Biochem Toxicol 3(Winter) 321-328. 

Curtis LR, Mehendale HM. 1981. Hepatobiliary dysfunction and inhibition of adenosine triphosphatase activity of bile canaliculi-enriched fractions following in vivo mirex, photomirex, and chlordecone exposures. Toxicol Appl Pharmacol 61 429-440. 

A familial deficiency in the bile-acid export pump, 103 which conveys bile acids from hepatocyte cytoplasm into bile canaliculi, increases the incidence of hepatocellular carcinoma in children. 

The hepatocyte secretes biliary fluid into the bile canaliculi (dark green), tubular intercellular clefts that are sealed off from the blood spaces by tight junctions. Secretory activity in the hepatocytes results in movement of fluid towards the canalicular space (A). The hepatocyte has an abundance of enzymes carrying out metabolic functions. These are localized in part in mitochondria, in part on the membranes of the rough (rER) or smooth (sER) endoplasmic reticulum. 

The bile canaliculi form a network, which feed into ductules, which become bile ducts (Fig. 6.3). The structural and functional unit of the liver is the lobule, which is usually described in terms of the hepatic acinus (Fig. 6.5), based on the microcirculation in the lobule. When the lobule is considered in structural terms, it may be described as either a classical or a portal lobule (see "Glossary"). The acinus comprises a unit bounded by two portal tracts and terminal hepatic or central venules, where a portal tract is composed of a portal venule, bile ductile, and hepatic arteriole (Fig. 6.5). Blood flows from the portal tract toward the central... 

Moslen. M.T.. Dunsford. H.A., Kamasuta, C., Chieco, P. Kanz, M.F. (1989) Histochemical and immunocytochemical evidence of early, selective bile canaliculi injury after 1,1-dichlor-ethylene in rats. Am. J. Pathol., 134, 1099-1112... 

In addition to hepatic parenchymal cells which are hepatocytes, hepatocyte stem cells, termed oval cells, are reported to be located in the canals of Hering where bile canaliculi from the hepatic cords converge on bile ductules of the portal triad. It is postulated that new hepatocytes travel down hepatic cords to replace the aging and damaged zone 3 hepatocytes. 

Biliary excretion. In the liver there is one active transport system for acids and one for bases, similar to those in the proximal renal tubule and, in addition, there is a system that transports un-ionised molecules, e.g. digoxin, into the bile. Small molecules tend to be reabsorbed by the bile canaliculi and in general only compounds that have a molecular weight greater than 300 are excreted in bile. (See also, enterohepatic circulation, p. 105)... 

J. Henle describes the bile canaliculi in the liver lobules as simple, unwalled intracellular spaces. 

The bile canaliculus is formed as a bile capillary by means of a groove-like canal in the intercellular space, bounded by 2 adjacent liver cells. The bile canaliculi have no walls of their own, but are surrounded by a special zone of the cell membrane (so-calledpericanalicular ectoplasm). Their diameter amounts to 0.5-1.0 pm. They are interconnected and form an extensive polygonal network. The surface area of the bile capillaries is increased by microvilli, which show great functionally determined variability. The canalicular membrane constitutes 10% of the total plasma membrane in the hepatocytes. Similar to the pericanalicular ectoplasm, the hepatocytes contain contractile microfilaments and other components of the cytoskel-eton. These canaliculi are supplied with carrier proteins and enzymes to control bile secretion. (2,34)... 

Steiner, J.W., Carruthers, J.S. Studies on the fine structure of the terminal branches of the biliary tree. I. The morphology of normal bile canaliculi, bile pre-ductules (Ducts of Hering) and bile ductules. Amer. J. Path. 1961 38 640-649... 

Mucoviscidosis or cystic fibrosis (CF) is indeed one of the most common autosomal recessive diseases. It is characterized by the production of a viscous secretion in the excretory glands. Accordingly, pancreatic cystic fibrosis can be observed in the pancreatic area and cylindrical bronchiectases in the pulmonary area. The inspissation of bile and mucus leads to obstruction of the bile canaliculi and subsequently to cholestasis. The gene product is characterized as cystic fibrosis transmembrane regulator (CFTR). (252) The gene defect, which is located on chromosome 7, causes a disorder of the intracellular transport of chloride ions (probably also of chloride ion secretion) and thus triggers the occurrence of CF. The incidence of mucoviscidosis is about 1 2,000-4,500. 

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