scholarly journals Inhibitory action of cyclobutyrol on the secretion of biliary cholesterol and phospholipids

1990 ◽  
Vol 266 (1) ◽  
pp. 165-171 ◽  
Author(s):  
M J Monte ◽  
R A Parslow ◽  
R Coleman
Keyword(s):  
Bile Acid ◽  
Serum Albumin ◽  
Acid Secretion ◽  
Isolated Perfused Rat Liver ◽  
Perfusion Fluid ◽  
Rat Serum ◽  
Canalicular Membrane ◽  
Bile Acid Secretion ◽  
Secretion Rates ◽  
Rat Serum Albumin

A number of organic anions are known to decrease biliary secretion of cholesterol and phospholipid without affecting bile acid secretion. Cyclobutyrol (CB) is a choleretic agent which also inhibits biliary lipid secretion. Using isolated perfused rat liver we have studied this inhibition in relation to possible mechanisms suggested for other anions. Shortly after its administration to the isolated perfused liver, CB decreases biliary outputs of cholesterol and phospholipid, without changes in bile acid secretion, at low (450 nmol/min), high (1350 nmol/min) and nil taurocholate infusion rates. The absolute inhibition does not appear to be decreased by elevated bile acid secretion. There is a differential effect on secretion of cholesterol and phospholipid, more marked at low bile acid secretion rates. Biliary outputs of the canalicular membrane enzymes 5′-nucleotidase and alkaline phosphodiesterase I are also depressed by CB administration, but the anion does not affect the biliary output of bovine serum albumin or the output of rat serum albumin into the perfusion fluid. Since CB does not inhibit intracellular vesicular transport or apparently inhibit intracanalicular events, its effect is different from the effect of several other anions. From these studies it appears that the most likely effect of CB is exerted at the level of the canalicular membrane.

scholarly journals Abnormal secretion of proteins into bile from colchicine-treated isolated perfused rat livers

1983 ◽  
Vol 216 (2) ◽  
pp. 409-414 ◽  
Author(s):  
S G Barnwell ◽  
R Coleman
Keyword(s):  
Serum Albumin ◽  
Protein Composition ◽  
Bile Canaliculus ◽  
Perfusion Fluid ◽  
Rat Serum ◽  
Essential Change ◽  
Rat Livers ◽  
Rat Bile ◽  
Rat Serum Albumin ◽  
Microtubular System

The microtubule poison, colchicine, caused an abnormal output of a variety of proteins into rat bile. After 3 h of exposure to the drug, livers were isolated and perfused with media of defined protein composition. There was no essential change in permeability of the hepatobiliary system to proteins (e.g. bovine serum albumin) entering bile from the perfusion fluid. The rat (serum) albumin and fibrinogen that were secreted into bile from colchicine-treated livers were probably derived from the hepatocytes. Disruption of the microtubular system reduces the secretion of proteins at the sinusoidal face of the hepatocyte and results in an accumulation of secretory vesicles in the cytoplasm. It is suggested that under these conditions some of the vesicles discharge their contents into the bile canaliculus.

Bile acid secretion and direct targeting of mdr1-green fluorescent protein from Golgi to the canalicular membrane in polarized WIF-B cells

1999 ◽  
Vol 112 (24) ◽  
pp. 4535-4545
Author(s):  
Y. Sai ◽  
A.T. Nies ◽  
I.M. Arias
Keyword(s):  
Bile Acid ◽  
B Cells ◽  
Acid Secretion ◽  
Intracellular Trafficking ◽  
Fluorescent Protein ◽  
Canalicular Membrane ◽  
Canalicular Transporters ◽  
Phosphoinositide 3 Kinase ◽  
Green Fluorescent ◽  
Bile Acid Secretion

The bile canalicular membrane contains several ATP-dependent transporters that are involved in biliary secretion. Canalicular transporters are synthesized in ER, modified in Golgi and transported to the apical plasma membrane. However, the route and regulation of intracellular trafficking of ATP-dependent transporters have not been elucidated. In the present study, we generated a translational fusion of mdr1 and green fluorescent protein and investigated bile acid secretion and intracellular trafficking of mdr1 in WIF-B cells, a polarized liver derived cell line. Similar to hepatocytes, WIF-B cells secrete bile acids and organic cations (i.e. rhodamine-123) into the bile canaliculi. Canalicular secretion of fluorescein isothiocyanate-glycocholate was stimulated by taurocholate and a decapeptide activator of phosphoinositide 3-kinase and was decreased by wortmannin. WIF-B9 cells were transiently and stably transfected with a mdr1-GFP construct. Fluorescence was observed in the canalicular membrane, pericanalicular punctate structures and Golgi region. Time lapse microscopy revealed that mdr1-GFP is transferred from Golgi as tubular vesicular structures the majority of which traveled directly to the canalicular membrane. Recycling between the canalicular membrane and subapical region was also observed. At no time was mdr1-GFP detected in the basolateral plasma membrane. At 15 degrees C, mdr1-GFP accumulated in Golgi; after a shift to 37 degrees C, fluorescence moved directly to the canalicular membrane. This process was enhanced by taurocholate and blocked by wortmannin. In these studies as well, no mdr1-GFP fluorescence was observed at any time in basolateral membranes or other intracellular organelles. In conclusion, in WIF-B cells, there is a direct route from Golgi to the canalicular membrane for trafficking of mdr1, a bile canalicular ATP-dependent transporter of organic cations. As in normal hepatocytes, phosphoinositide 3-kinase regulates bile acid secretion and intracellular trafficking of mdr1 in WIF-B cells. WIF-B cells stably transfected with mdr1-GFP provide an important model in which to study trafficking and regulation of canalicular transporters. Movies available on-line: http://www.healthsci.tufts.edu/LABS/IMArias+++/Sai_F9.html

Bile Lipid Secretion in Obese and Non-Obese Individuals with and without Gallstones

1985 ◽  
Vol 69 (1) ◽  
pp. 71-79 ◽  
Author(s):  
A. Reuben ◽  
P. N. Maton ◽  
G. M. Murphy ◽  
R. H. Dowling
Keyword(s):  
Bile Acid ◽  
Acid Secretion ◽  
Biliary Lipid ◽  
Biliary Cholesterol ◽  
Cholesterol Gallstones ◽  
Lipid Secretion ◽  
Biliary Cholesterol Secretion ◽  
Cholesterol Secretion ◽  
Bile Acid Secretion ◽  
Secretion Rates

1. Biliary lipid secretion rates were measured in non-obese and obese individuals with and without cholesterol gallstones, using a steady-state, amino acid duodenal perfusion method. In addition, biliary lipid secretion rates were measured in five obese gallstone patients receiving high-dose chenodeoxycholic acid therapy (16-22 mg day−1 kg−1). 2. Bile acid secretion rates in the non-obese patients with cholesterol gallstones (563+sem 70 μmol/h, n = 6) were significantly lower than in the non-obese controls (1078 + 210 μmol/h, n = 10, P < 0.05), whereas cholesterol secretion rates were similar in the non-obese individuals with and without gallstones (51+7 and 42+4 μmol/h respectively). 3. In the obese, both with and without gallstones, the major abnormality was hypersecretion of cholesterol (107+7 μmol/h, n = 7, and 81 + 15 μmol/h, n = 7, respectively). Both these values were significantly greater than those in the non-obese controls (P < 0.01-0.02). 4. Biliary cholesterol secretion rates correlated significantly with bile acid secretion rates but, for every mole of bile acid secreted, the obese secreted more cholesterol than the non-obese. 5. Chenodeoxycholic acid treatment lowered biliary cholesterol saturation in obese gallstone patients by reducing biliary cholesterol secretion. 6. These results suggest that there are two major types of defect in biliary lipid secretion in gallstone patients: reduced biliary bile acid secretion in non-obese gallstone patients and excessive biliary cholesterol secretion in the obese.

Mechanism by which cAMP activates PI3-kinase and increases bile acid secretion in WIF-B9 cells

2002 ◽  
Vol 283 (6) ◽  
pp. C1655-C1666 ◽  
Author(s):  
Tatehiro Kagawa ◽  
Lyuba Varticovski ◽  
Yoshimichi Sai ◽  
Irwin M. Arias
Keyword(s):  
Bile Acid ◽  
Acid Secretion ◽  
Cell Lines ◽  
Membrane Vesicles ◽  
Fluorescein Isothiocyanate ◽  
Dominant Negative ◽  
Independent Manner ◽  
Canalicular Membrane ◽  
Bile Acid Secretion ◽  
K Activity

Previous studies in rat bile canalicular membrane vesicles and WIF-B9 cells revealed that cAMP-induced trafficking of ATP-binding cassette (ABC) transporters to the canalicular membrane and their activation require phosphoinositide 3-kinase (PI3-K) products. In the present studies, canalicular secretion of fluorescein isothiocyanate-glycocholate in WIF-B9 cells was increased by cAMP and a decapeptide that enhances PI3-K activity; these effects were inhibited by wortmannin. To determine the mechanism(s) whereby cAMP activates PI3-K, we examined signal transduction pathways in WIF-B9 and COS-7 cells. cAMP activated PI3-K in both cell lines in a phosphotyrosine-independent manner. PI3-K activity increased in association with p110β in both cell lines. The effect of cAMP was KT-5720 sensitive, suggesting involvement of protein kinase A. Expression of a dominant-negative β-adrenergic receptor kinase COOH terminus (β-ARKct), which blocks Gβγ signaling, decreased PI3-K activation in both cell lines. cAMP increased GTP-bound Ras in COS-7 but not WIF-B9 cells. Expression of dominant-negative Ras abolished cAMP-mediated PI3-K, which suggests that the effect is downstream of Ras and Gβγ. These data indicate that cAMP activates PI3-K in a cell type-specific manner and provide insight regarding mechanisms of PI3-K activation required for bile acid secretion.

scholarly journals Mechanisms by which cAMP increases bile acid secretion in rat liver and canalicular membrane vesicles

2003 ◽  
Vol 285 (2) ◽  
pp. G316-G324 ◽  
Author(s):  
Suniti Misra ◽  
Lyuba Varticovski ◽  
Irwin M. Arias
Keyword(s):  
Bile Acid ◽  
Acid Secretion ◽  
Rat Liver ◽  
Abc Transporters ◽  
Intracellular Trafficking ◽  
Membrane Vesicles ◽  
Canalicular Membrane ◽  
Pi3k Activity ◽  
Dependent Transport ◽  
Bile Acid Secretion

Bile acid secretion induced by cAMP and taurocholate is associated with recruitment of several ATP binding cassette (ABC) transporters to the canalicular membrane. Taurocholate-mediated bile acid secretion and recruitment of ABC transporters are phosphatidylinositol 3-kinase (PI3K) dependent and require an intact microtubular apparatus. We examined mechanisms involved in cAMP-mediated bile acid secretion. Bile acid secretion induced by perfusion of rat liver with dibutyryl cAMP was blocked by colchicine and wortmannin, a PI3K inhibitor. Canalicular membrane vesicles isolated from cAMP-treated rats manifested increased ATP-dependent transport of taurocholate and PI3K activity that were reduced by prior in vivo administration of colchicine or wortmannin. Addition of a PI3K lipid product, phosphoinositide 3,4-bisphosphate, but not its isomer, phosphoinositide 4,5-bisphosphate, restored ATP-dependent taurocholate in these vesicles. Addition of a decapeptide that activates PI3K to canalicular membrane vesicles increased ATP-dependent transport above baseline activity. In contrast to effects induced by taurocholate, cAMP-stimulated intracellular trafficking of the canalicular ABC transporters was unaffected by wortmannin, and recruitment of multidrug resistance protein 2, but not bile salt excretory protein (bsep), was partially decreased by colchicine. These studies indicate that trafficking of bsep and other canalicular ABC transporters to the canalicular membrane in response to cAMP is independent of PI3K activity. In addition, PI3K lipid products are required for activation of bsep in the canalicular membrane. These observations prompt revision of current concepts regarding the role of cAMP and PI3K in intracellular trafficking, regulation of canalicular bsep, and bile acid secretion.

scholarly journals The Biosynthesis of Rat Serum Albumin

1972 ◽  
Vol 247 (12) ◽  
pp. 3858-3863 ◽  
Author(s):  
Theodore Peters ◽  
James C. Peters
Keyword(s):  
Serum Albumin ◽  
Rat Serum ◽  
Rat Serum Albumin

scholarly journals Bile acid secretion by cultured rat hepatocytes. Regulation by cholesterol availability.

1983 ◽  
Vol 258 (6) ◽  
pp. 3661-3667 ◽  
Author(s):  
R A Davis ◽  
P M Hyde ◽  
J C Kuan ◽  
M Malone-McNeal ◽  
J Archambault-Schexnayder
Keyword(s):  
Bile Acid ◽  
Acid Secretion ◽  
Rat Hepatocytes ◽  
Cultured Rat Hepatocytes ◽  
Bile Acid Secretion
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