Hepatocytes tight junctions

PJ Lowe, K Miyal, JH Steinbach, WGM Hardison. (1988). Hormonal regulation of hepatocyte tight junctional permeability. Am J Physiol 255 G454-G461. 

J Llopis, GEN Kass, SK Duddy, GA Moore, S Orrenius. (1991). Mobilization of hormone sensitive calcium pool increases hepatocyte tight junctional permeability in the perfused rat liver. FEBS Lett 280 84-86. 

Lora, L. Mazzon, E. et al. (1997). "Hepatocyte tight-junctional permeability is increased in rat experimental colitis." Gastroenterology, 113(4), 1347-54. 

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. 

Fig. 6 Multi-drug transporters in the human liver hepatocytes. Abbreviations TJ Tight junction. (Reproduced from [4])...

Fig. 2.9 Liver cell and sinusoidal cells with organelles and polarized membrane compartments hepatocytes (H), sinusoids (S), Disse s space (D), erythrocytes (ER), endothelial cells (E), Kupffer cells (K), Ito cells (I), microvilli (MV), canahculus (BC), nucleolus (N), tight junctions (tj), cell nucleus (CN), mitochondria (M), smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER), Golgi apparatus (GA), lysosomes (L), peroxisomes (P), ribosomes (R), microfilaments (ME) (modified from L. Cossel) (s. figs. 2.16-2.18)...

Primary bile, already containing various compounds (= solutes) collected during transcellular transport, is formed by osmotic filtration at the canalicular membrane of the hepatocytes. It is yellow to orange in colour. Para-cellular incorporation of further solutes into the bile occurs via the intercellular gap and the tight junctions. The canalicular bile flow comprises two fractions ... 

Bile produced by hepatocytes is secreted into the bile canaliculi between adjacent hepatic cells. The wall of the canaliculus is formed by the plasma membrane of the hepatocytes, which are held together by tight junctions. Canaliculi arise near central veins and extend to the periphery of the lobules. The direction of bile flow in the canaliculi is centrifugal, whereas that of the blood flow is centripetal. Canaliculi coalesce to form ducts, which are lined by epithelium, and the ducts coalesce to form the right and left hepatic ducts. Outside the liver these ducts form the common hepatic duct. 

Each day hepatocytes secrete about 1L of bile, consisting mostly of water, ions, bile salts (important for the absorption of lipids), cholesterol, and bile pigments. Bile formation by hepatocytes requires the active secretion of inorganic and organic solutes into the canalicular lumen, followed by the movement of water. Other solutes can be carried with this movement of water through the tight junctions between hepatocytes. 

Rassat, J. Robenek, H. et al. (1982). "Alterations of tight and gap junctions in mouse hepatocytes following administration of colchicine." Cell Tissue Res, 223(1), 187-200. 

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