Bile Flow Rate Research Articles

Neurotensin elevates hepatic bile acid secretion in chickens by a mechanism requiring an intact enterohepatic circulation.

Neurotensin (NT), given intravenously at 10-50 pmol/kg per min to anesthetized female chickens equipped with a bile duct fistula, dose-dependently elevated hepatic bile flow and bile acid output but only when the enterohepatic circulation was maintained by returning the bile to the intestinal lumen. Infusion of NT at 10 and 50 pmol/kg per min increased the average hepatic bile acid output over a 30-min period to 138 +/- 11 and 188 +/- 13% of control, respectively. During infusion of NT, plasma levels of immunoreactive NT (iNT) increased in time from the basal level (14 +/- 1.3 pM) to reach steady state at 30 min. There was a near linear relationship between the dose of NT infused and the increment in plasma iNT. In addition, infusion of NT at 40 pmol/kg min gave a plasma level of iNT (approximately/= 88 pM) which was within the range of those observed during duodenal perfusion with lipid (54-300 pM) and near to that measured in hepatic portal blood from fed animals (52 +/- 5 pM). Perfusion of duodenum with lipid released endogenous NT and increased the rate of hepatic bile flow. When NT antagonist SR48692 was given, bile flow rate decreased to the basal level. These results suggest that intestinal NT, released by lipid, may participate in the regulation of hepatic bile acid output by a mechanism requiring an intact enterohepatic circulation.

Biliary excretory function is regulated by canalicular membrane fluidity associated with phospholipid fatty acyl chains in the bilayer: implications for the pathophysiology of cholestasis.

Bile canalicular membrane fluidity is modulated by phospholipid molecular species within membrane lipid bilayers. Thus, organellar membrane lipid composition is a determinant of canalicular function. In this study, the effect of phalloidin-induced cholestasis on bile lipid composition and liver subcellular membrane fraction composition in rats was examined to clarify the relationship between cholestasis and hepatic lipid metabolism. Each rat received one phalloidin dose (400 microg/kg, i.v.). After the bile was collected, liver microsomes and canalicular membranes were analysed. The bile flow rate decreased by 50% 3.5 h after phalloidin administration. Although the bile acid output remained almost the same, the phospholipid and cholesterol output were significantly decreased (by 40.3+/-5.97% and 76.9+/-5.56%, respectively). Thus, the cholesterol:phospholipid (C:P) ratio in bile was significantly decreased by 80.4+/-10.1%. Phalloidin administration also increased the saturated: unsaturated fatty acid ratio (S:U) in bile for phosphatidylcholine by 25.5+/-3.2%. In the canalicular membrane, the C:P and S:U ratios for phosphatidylcholine were increased (24.8+/-4.2% and 34.4+/-6.9%, respectively), while the S:U for sphingomyelin was decreased by 61.0+/-6.2%. In microsomes, the C:P was decreased by 41.0+/-6.0%, but the S:U for both phosphatidylcholine and sphingomyelin were unaffected. Canalicular membrane fluidity, assayed by 1,6-diphenyl-1,3,5-hexatriene fluorescence depolarization, decreased significantly. Therefore, increased secretion of hydrophobic phosphatidylcholine into bile was associated with more hydrophobic canalicular membrane phosphatidylcholine, while sphingomyelin in the canalicular membrane was less hydrophobic. These results indicate that phalloidin uncouples secretion of cholesterol and phospholipids, which causes a redistribution of fatty acyl chain species among canalicular membrane phospholipids that alters membrane fluidity. These changes may be a homeostatic response mediated by the phospholipid translocator in the canalicular membrane, although direct evidence for this is unavailable.

Secretion of Insulin-Like Growth Factor-II into Bile of Rats of Different Ages

Bile from rats of different ages (suckling 10–12 days; weanling 30–33 days, and adult 60–70 days) was collected and studied for the presence of immuno- and receptor-assayable insulin-like growth factor-II (IGF-II) concentrations. Concentrations of RIA IGF-II in bile were highest in suckling rats (230 ± 38 ng/ml) and lowest in adults (47 ± 7 ng/ml). These concentrations were approximately twice those of the bile IGF-I concentration in sucklings, as measured in a previous study. Selected bile samples were also assayed using a competitive binding assay with a crude preparation of adult rat liver membranes bearing the IGF-II receptor. These studies confirmed the presence of receptor- (as well as immuno-) active IGF-II in bile. Since bile flow rates increased dramatically after the suckling period, bile delivery rates of IGF-II were normalized as picograms per gram body weight per hour. When such calculations were done, bile IGF-II delivery rates to the small intestine were highest in sucklings and weanlings in comparison to adult rats. Thus non-enterically derived (milk- and bile-borne) IGF-II delivery to the suckling small intestine can be approximated at roughly 1 μg/day. Unlike IGF-I, intravenously injected IGF-II could not be detected in suckling bile, suggesting a predominantly hepatic origin. From this study we conclude that there exists a significant delivery of receptor-active IGF-II to the gastrointestinal tract of rats of all ages.

The function of alkaline phosphatase in the liver: Regulation of intrahepatic biliary epithelium secretory activities in the rat

We studied the effects of alkaline phosphatase (AP) on the secretory processes of the rat intrahepatic biliary epithelium as well as the role of the intrahepatic biliary epithelium in the uptake and biliary secretion of exogenous AP. The effects of acute and chronic administration of AP on bile secretory parameters were investigated in vivo in normal and bile duct ligated (BDL) rats and in vitro in isolated rat bile duct units (IBDU).In vivo, acute AP administration decreased bile flow and biliary bicarbonate excretion and abolished secretin choleresis in BDL rats but not in normal rats. On the contrary, the AP inhibitor, levamisole, increased in BDL rat bile flow and biliary bicarbonate excretion. In vitro, basal and secretin-stimulated Cl−/HCO3− exchanger activity in IBDU was immediately inhibited by AP intraluminal microinjection (apical exposure) but only after a prolonged exposure to the basolateral pole. Levamisole increased the Cl−/HCO3− exchanger activity of IBDU. A significant basolateral uptake of AP occurs in IBDU with a progressive transport to the apical domain. AP chronic treatment increased AP and γ-glutamyltranspeptidase (γ-GT) activities in the intrahepatic bile ducts and hepatocyte canalicular pole, promoted enlargement of bile canaliculi, and decreased bile flow and biliary bicarbonate excretion. In conclusion, the intrahepatic biliary epithelium plays a role in the uptake and biliary secretion of serum AP. AP inhibits the secretory processes of the intrahepatic biliary epithelium and induces features of intrahepatic cholestasis after chronic administration. These findings indicate that AP plays an active role in down-regulating the secretory activities of the intrahepatic biliary epithelium. (Hepatology 2000;32:174-184.)

Role of perivenous hepatocytes in taurolithocholate-induced cholestasis in vivo

The magnitude of cholestasis induced by taurolithocholic acid (TLCA) and its relationship with phase I metabolism were analyzed in rats treated with bromobenzene (BZ), a chemical that causes selective necrosis of perivenous (zone 3) hepatocytes. Forty-eight hours after BZ administration (600 mg/Kg bw), a single dose of 20 μmol/Kg bw of TLCA was injected. Bile was collected during 180 min and bile flow and total bile acid excretion rate were determined. Biliary bile acid composition was analyzed by gas–liquid chromatography-mass spectrometry. BZ administration did not affect the development of TLCA-induced cholestasis, but exacerbated the bile acid-induced decrease in bile flow during the period of recovery from cholestasis. Biliary excretion of total bile acids after TLCA injection relative to basal value was not effected by BZ. The analysis of bile acid composition in bile revealed that TLCA was partially converted to hyodeoxycholic and muricholic acids. The cumulative excretion of all exogenous bile acids and their contribution to the composition of the biliary bile acid pool were not substantially affected by zone 3 necrosis, suggesting that synthesis and secretion of hydroxylated derivatives of TLCA were maintained by zone 1 and 2 hepatocytes. The relative content of endogenous bile acids was not affected by BZ during TLCA-induced cholestasis. Thus, it seems unlikely that the exacerbation of the cholestasis in BZ-treated rats is due to different choleretic properties and/or toxicity of the bile acid pool.

Biliary indocyanine green excretion as a predictor of hepatic adenosine triphosphate levels in patients with obstructive jaundice

Background: Correlation of the hepatic adenosine triphosphate (ATP) level with indocyanine green (ICG) excretion into bile was examined in patients with obstructive jaundice after the relief of hyperbilirubinemia by preoperative percutaneous transhepatic biliary drainage (PTBD). Methods: Patients with complete bile duct obstruction, the mean serum total bilirubin concentration being 13.6 ± 8.5 (SD) mg/dL, underwent PTBD prior to surgery. Within a few days before surgery when the mean serum total bilirubin level decreased to 1.2 mg/dL, ICG (0.5 mg/kg) was intravenously injected, and the whole bile was collected at 1-hour intervals for 5 hours. The ICG concentration in bile, bile flow rate, amount of ICG excreted in bile, and biliary ICG excretion rate as percentage of the injected dose were determined. At the time of surgery, a small liver tissue sample was obtained immediately after laparotomy without any ischemic procedures, and ATP concentrations were determined. Results of hepatic ATP levels were correlated with laboratory and clinical determinations. Results: The bile flow rate was essentially constant during the 5-hour period, the mean value being 21 mL/hour. The ICG concentrations in bile gradually increased, reached the maximal level in 3 hour, and declined thereafter. The biliary ICG excretion rate for 5 hours was 40% ± 18% of its injected dose. The biliary ICG excretion rate and amount of ICG excreted in bile for 5 hours significantly ( P <0.05) correlated with the hepatic ATP level. The decline index of serum bilirubin during PTBD was also correlated with the hepatic ATP level. The serum ICG retention rate, bile flow rate, maximal ICG concentration in bile, and other liver function tests including serum albumin and cholinesterase levels did not correlate with the hepatic ATP level. Conclusions: Both the amount of and excretion rate of ICG in bile reflect the hepatic ATP level. Determination of biliary ICG excretion contributes to precise evaluation of hepatic energy status before surgery in patients with obstructive jaundice.

Increased Sinusoidal Pressure Is Associated with Early Liver Weight Gain in Ischemia–Reperfusion Injury in Isolated Perfused Rat Liver

Background. Hepatic ischemia–reperfusion (I/R) is accompanied by liver weight gain and ascites formation. This could be caused by an increase in sinusoidal pressure, a determinant of hepatic transvascular fluid movement. We determined the role of sinusoidal pressure, assessed by triple vascular occlusion pressure (Pto), in the I/R injury in isolated rat livers perfused with leukocyte-free diluted blood bivascularly via the portal vein and hepatic artery.Materials and methods. Ischemia was induced at room temperature by occlusion of either the inflow lines of the hepatic artery and portal vein (the open outflow group, n = 10) or both the inflow and the outflow (hepatic venous) lines (the closed outflow group, n = 10) for 1 h, followed by 1-h reperfusion in a recirculating manner.Results. Liver weight in both groups increased biphasically after reperfusion; the initial peak occurred at 3 min and the second peak at 60 min. Immediately after reperfusion, Pto peaked, followed by a gradual decline. The initial weight increase in groups combined was significantly and positively correlated with an increase in Pto (r = 0.716, P = 0.0002), but the second peak was independent of Pto. Liver injury, assessed by perfusate levels of hepatic enzymes and reduced bile flow rate, was observed at 60 min after reperfusion in both groups.Conclusions. These findings suggest that increased sinusoidal pressure contributes to only the early liver weight gain after reperfusion in isolated perfused rat livers. The late weight gain may be presumably due to liver injury.

Effects of Re-Arterialization on Early Graft Function and Regeneration in the Rat Model of Heterotopic Auxiliary Liver Transplantation

In the rat model of heterotopic auxiliary liver transplantation, graft re-arterialization may influence the outcome of inter-liver competition. This was investigated in the current study using two transplanted groups with or without graft re-arterialization. Immediately after reperfusion, the re-arterialized grafts showed significantly higher bile flow rate and bilirubin excretion than the grafts without re-arterialization. DNA synthesis rate was also increased more drastically in the re-arterialized group following the transplantation. Without re-arterialization, the rats developed more pronounced cytolysis and cholestasis. Among the long-term survivors, all healthy re-arterialized grafts regenerated, whereas 5/6 non-re-arterialized grafts atrophied. These data demonstrate that the re-arterialization increases graft survival by improving early hepatic function, enhancing regenerative response and preventing post-transplant biliary complications in this rat model.

FACTORS THAT AFFECT ABSORPTION BEHAVIOR OF CYCLOSPORIN A IN GENTAMICIN-INDUCED ACUTE RENAL FAILURE IN RATS

Factors that affect the absorption of cyclosporin A (CsA) were examined in gentamicin-induced acute renal failure (ARF) rats. In ARF rats, the area under the blood CsA concentration-time curve after oral administration was significantly decreased in comparison with that of control rats; 5.81 ± 0.55 vs 11.30 ± 1.59 mg h mL−1 (mean ± s.e.m.), respectively, and the relative bioavailabilities in ARF and control rats after oral administration were 15.2% and 43.4%, respectively. The flow rate of bile and the amount of bile acids in ARF rats were markedly decreased to about 61% of control, and 41% of control, respectively. The amount of CsA uptaken into the evened sac of jejunum, transferred to serosal side, and metabolized in tissues was significantly decreased in ARF rats without verapamil, while with 0.3 mM verapamil, the amount in ARF rats recovered to the levels of control rats. The absorption clearance of CsA in ARF rats was significantly decreased, however it was significantly improved by adding bile or bile acid. Adenosine triphosphate released from enterocytes in ARF rats was significantly decreased in the presence of 2.0 1−M CsA, 0.3 mM verapamil, or both, in comparison with control rats. From these findings, we concluded that a reduction of CsA bioavailability during ARF is caused by depression in bile excretion and renal function-dependent depression of uptake from intestinal tract via maybe P-gLycoprotein in enterocytes. They are main two factors that reduce the absorbed fraction of CsA in ARF rats.

Effects of clofibrate and indocyanine green on the hepatobiliary disposition of acetaminophen and its metabolites in male CD-1 mice

1. The effects of clofibrate (CFB) and indocyanine green (ICG) on the biliary excretion of acetaminophen (APAP) and its metabolites were investigated. 2. Male CD-1 mice were pretreated with 500 mg CFB/kg, i.p. for 10 days. Controls received corn oil vehicle only. After overnight fasting, common bile duct-cannulated mice were challenged with a non-toxic dose of APAP (1 mmol/kg, i.v.). 3. CFB pretreatment did not affect bile flow rate, nor did it affect the cumulative biliaryexcretion of APAP and its conjugated metabolites. 4. Additional CFB or corn oil pretreated mice were given 30 μmol indocyanine green(ICG)/kg, i.v., immediately before APAP dosing. ICG is a non-metabolizable organic anion that is completely excreted into the bile through a canalicular transport process for organic anions. 5. ICG significantly decreased the bile flow rate and biliary concentration of APAPglutathione, APAP-glucuronide and APAP-mercapturate within the first hour after dosing without affecting the biliary concentration of APAP.6. The results indicate thatCFB pretreatment does not affect the total amount of APAP and its metabolites excreted in bile. They also suggest that the biliary excretion of several conjugated metabolites of APAP share the same excretory pathway with the organic anion ICG.

Choleretic activity of phloracetophenone in rats: structure–function studies using acetophenone analogues

The relationship between the chemical structure and choleretic activity of phloracetophenone (2,4,6-trihydroxyacetophenone) was investigated in adult male rats. Fourteen acetophenone analogues, with different substituents on the benzene nucleus, were intraduodenally administered and bile samples were collected via a bile fistula. All of the compounds tested immediately induced choleresis. For the same number of substituents on the benzene ring, hydroxy analogues induced a greater choleresis. The number and position of hydroxy substituents on the benzene nucleus play an important role in determining choleretic activity and biliary secretion of bile acid, but had no relation to biliary excretion of cholesterol. The choleretic activity of the hydroxylated compounds was inversely related to hydrophobicity, as inferred by thin-layer chromatography (TLC). Among the hydroxylated acetophenone analogues, 2,4,6-trihydroxyacetophenone was identified as the most potent, with a choleretic activity of 231.8±6.1 μl/mmol/min. It induced both a high bile flow rate and a high bile salt output and led to lower plasma cholesterol levels. This bile had a low lithogenic potential. The results suggest that a structural requirement for high choleretic activity of 2,4,6-trihydroxyacetophenone is a substituent hydroxy group at 4-position. Additional hydroxy groups at 2- and 6-positions are essential for the induction of higher an output of bile acid, and possibly, other solid materials.

Phenotypic characterization of Lith genes that determine susceptibility to cholesterol cholelithiasis in inbred mice: pathophysiology of biliary lipid secretion

The inbred C57L strain but not the AKR strain of mice carry Lith genes that determine cholesterol gallstone susceptibility. When C57L mice are fed a lithogenic diet containing 15% fat, 1% cholesterol, and 0.5% cholic acid, gallbladder bile displays rapid cholesterol supersaturation, mucin gel accumulation, increases in hydrophobic bile salts, and rapid phase separation of solid and liquid crystals, all of which contribute to the high cholesterol gallstone prevalence rates (D. Q-H. Wang, B. Paigen, and M. C. Carey. J. Lipid Res. 1997. 38: 1395;-1411). We have now determined the hepatic secretion rates of biliary lipids in fasting male and female C57L and AKR mice and the intercross (C57L x AKR)F(1) before and at frequent intervals during feeding the lithogenic diet for 56 days. Bile flow and biliary lipid secretion rates were measured in the first hour of an acute bile fistula and circulating bile salt pool sizes were determined by the "washout" technique after cholecystectomy. Compared with AKR mice, we found that i) C57L and F(1) mice on chow displayed significantly higher secretion rates of all biliary lipids, and larger bile salt pool sizes, as well as higher bile salt-dependent and bile salt-independent flow rates; ii) the lithogenic diet further increased biliary cholesterol and lecithin outputs, but bile salt outputs remained constant. Biliary coupling of cholesterol to lecithin increased approximately 30%, setting the biophysical conditions necessary for cholesterol phase separation in the gallbladder; and iii) no gender differences in lipid secretion rates were noted but male mice exhibited significantly more hydrophobic bile salt pools than females. We conclude that in gallstone-susceptible mice, Lith genes determine increased outputs of all biliary lipids but promote cholesterol hypersecretion disproportionately to lecithin and bile salt outputs thereby inducing lithogenic bile formation.

In vivo protection of the pig liver against ischemia/reperfusion injury by tauroursodeoxycholate.

Tauroursodeoxycholate (TUDC) is used routinely in the treatment of cholestatic liver disease. The present study was designed to determine whether it would mitigate ischemia/reperfusion injury in an in vivo pig liver-transplantation model. Transplantation was performed in 12 animals after a preservation time of 8 h. In the control group (n=6), 0.9% saline was infused into the donor. In the experimental group (n=6), TUDC was given intravenously at a rate of 2 micromol/kg body weight per minute. In the recipient, infusion was started at the time of reperfusion; saline was infused for 400 min in the control group, TUDC for the same duration at a rate of 0.2 micromol/kg body weight per minute in the experimental group. Blood was drawn for determination of liver enzymes. Bile samples were collected and bile flow (BF) and bile salt secretion rate (BSSR) were determined. One-week survival was 92% and not different among groups. Liver enzymes were lower in the TUDC group than the saline group. Prior to TUDC infusion in the donor animals, there were no differences in BF and BSSR. After infusion of TUDC, BF and BSSR were highly significantly different than the control group. Infusion of TUDC in pig livers protects against ischemia/reperfusion injury in vivo. This might be due to the membrane-stabilizing effect of TUDC. Preconditioning of liver grafts with TUDC could potentially lead to improved liver function post-transplantation.

Communication via gap junctions modulates bile secretion in the isolated perfused rat liver

Background & Aims: Bile secretion is regulated in part by adenosine 3',5'-cyclic monophosphate (cAMP) and cytosolic Ca 2+ (Ca 2+ i). Hormone receptors that link to these second messengers are not uniformly distributed across the hepatic lobule, but both cAMP and Ca 2+ i cross gap junctions, so we tested whether gap junctional communication plays a role in changes in bile flow induced by the activation of these receptors. Methods: cAMP levels in isolated perfused rat livers were increased by using glucagon, because glucagon receptors are predominantly on pericentral hepatocytes, or by using dibutyryl cAMP, which acts on hepatocytes throughout the hepatic lobule. Ca 2+ i concentration was increased by using vasopressin, because V 1a receptors are most heavily expressed on pericentral hepatocytes, or by using 2,5-di( tert-butyl)-1,4-benzo-hydroquinone ( t-BuBHQ), which increases the Ca 2+ i concentration in hepatocytes throughout the hepatic lobule. We used 18α-glycyrrhetinic acid (αGA) to block gap junction conductance, which was assessed by fluorescence recovery after photobleaching. Results: αGA blocked fluorescence recovery after photobleaching without altering the basal rate of bile flow. Glucagon and dibutyryl cAMP increased bile flow; αGA blocked the glucagon-induced increase but not that induced by dibutyryl cAMP. Vasopressin and t-BuBHQ decreased bile flow; αGA exacerbated the decrease induced by vasopressin but not by t-BuBHQ. Conclusions: Glucagon and vasopressin modulate bile flow in a manner that depends in part on gap junctional communication, even though the two hormones activate second messengers with opposing effects on bile flow. The organization of second messenger signals across the hepatic lobule may be an important component of hormonal regulation of bile secretion. GASTROENTEROLOGY 1999;116:1176-1183

Cholic acid aids absorption, biliary secretion, and phase transitions of cholesterol in murine cholelithogenesis.

Cholic acid is a critical component of the lithogenic diet in mice. To determine its pathogenetic roles, we fed chow or 1% cholesterol with or without 0.5% cholic acid to C57L/J male mice, which because of lith genes have 100% gallstone prevalence rates. After 1 yr on the diets, we measured bile flow, biliary lipid secretion rates, hepatic cholesterol and bile salt synthesis, and intestinal cholesterol absorption. After hepatic conjugation with taurine, cholate replaced most tauro-beta-muricholate in bile. Dietary cholic acid plus cholesterol increased bile flow and biliary lipid secretion rates and reduced cholesterol 7alpha-hydroxylase activity significantly mostly via deoxycholic acid, cholate's bacterial 7alpha-dehydroxylation product but did not downregulate cholesterol biosynthesis. Intestinal cholesterol absorption doubled, and biliary cholesterol crystallized as phase boundaries shifted. Feeding mice 1% cholesterol alone produced no lithogenic or homeostatic effects. We conclude that in mice cholic acid promotes biliary cholesterol hypersecretion and cholelithogenesis by enhancing intestinal absorption, hepatic bioavailability, and phase separation of cholesterol in bile.

Intravenous fish oil emulsion attenuates total parenteral nutrition-induced cholestasis in newborn piglets.

Total parenteral nutrition (TPN) causes intrahepatic cholestasis and membrane phospholipid changes. Fatty acid (FA) composition of bile and hepatocyte phospholipid is influenced by dietary FA composition. We hypothesized that altering FA composition of i.v. lipid emulsions modifies 1) severity of TPN-induced cholestasis; 2) hepatocyte membrane composition and function; 3) bile flow and composition. Newborn piglets received either sow's milk, TPN with i.v. soybean oil or TPN with i.v. fish oil (FO). After 3 wk, basal and stimulated bile flow were measured after bolus injections of 20, 50, and 100 micromol/kg of taurocholate (TCA). Bile was analyzed for bile acids, cholesterol, phospholipids, and phospholipid-FA. Sinusoidal and canalicular membrane PL-FA, fluidity, and Na+/K+-ATPase were measured. Although the soybean oil-fed animals developed cholestasis, the FO and milk group had similar liver and serum bilirubin. Basal and stimulated bile flow rates were impaired in the soybean oil but not in the FO group. Hepatocyte membrane FA composition reflected dietary FA. Changes in sinusoidal and canalicular membrane fluidity and sinusoidal Na+/K+-ATPase activity did not explain the effect of FO on TPN-induced cholestasis. Intravenous FO reduces TPN-induced cholestasis by unknown mechanisms.

Estradiol replacement in ovariectomized rats increases the hepatic concentration and biliary secretion of α-tocopherol and polyunsaturated fatty acids

Previously, we showed that estradiol replacement in ovariectomized rats produced prominent increases in serum and liver α-tocopherol (αTP). The present study was conducted to examine whether the estrogen-induced increase in the liver concentrations of αTP affects its biliary secretion and the fatty acid compositions of hepatic and biliary lipids. Ten ovariectomized rats were assigned to two groups: five rats were implanted subcutaneously with time-release estradiol pellets (OXE; 25 μg/day/rat) and five with placebo (OXP). Twice daily rats were pair-fed a modified AIN-93G diet containing soybean oil. At 5 weeks, bile was collected via a bile cannula hourly for 8 hours during duodenal infusion of a lipid emulsion (565 μmol triolein and 396 μmol Na-taurocholate/24 mL phosphate buffered saline, pH 6.45) at 3.0 mL/hr. During the 8-hour period, no difference was noted in the hourly rate of bile flow (0.95 mL/hr in OXE rats vs. 0.99 mL/hr in OXP rats). The biliary output of αTP for 8 hours was higher in OXE rats (51.6 ± 3.6 nmol) than OXP rats (31.7 ± 2.9 nmol). Likewise, the liver concentration of αTP was higher in OXE rats (81.9 ± 3.5 nmol/g liver) than in OXP rats (53.3 ± 7.4 nmol/g liver). The biliary secretion of phospholipids (PL) for 8 hours was significantly ( P < 0.05) higher in OXE rats (55.1 ± 4.9 μmol) than in OXP rats (42.3 ± 4.7 μmol). Among the PL fatty acids, the outputs of 20:4 and 22:6n-3 were increased most markedly by estradiol replacement. The total outputs of 22:6n-3 for 8 hours in OXE and OXP rats were 2.95 ± 0.20 μmol and 1.37 ± 0.23 μmol, respectively. In the liver, the concentrations of PL 22:5n-3 and 22:6n-3 were elevated significantly in OXE rats. The present results suggest that estradiol may protect hepatic PL and membranes against oxidative damage by improving the liver status of αTP.

Biliary bacterial infection decreased the secretion of bile acids and bilirubin into bile

Background: Bacterial cholangitis is frequently associated with serious complications. Methods: The plasma disappearance rates and the biliary output of bile acids and bilirubin after percutaneous transhepatic biliary drainage (PTBD) were examined in 29 patients with extrahepatic biliary obstruction. Results: Twenty-nine patients were divided into the bacteria-minus (n = 17) and bacteria-plus (n = 12) groups. Decreases in the plasma bile acid and bilirubin levels of the bacteria-minus group (t 1/2 = 0.38 and 3.8 days for bile acids and bilirubin, respectively) were faster than those of the bacteria-plus group (t 1/2 = 1.7 and 7.5 days). The bile flow rate was significantly increased in the bacteria-plus group compared with the bacteria-minus group. The calculated values of bilirubin and bile acid in the bile were higher in the bacteria-minus group than in the bacteria-plus group. Conclusions: Bacterial colonization in the bile stimulates bile duct cells to increase bile volume and inhibits the hepatocyte transport activity of bile acids and bilirubin.

Cholestatic effects of the K+ channel blockers Ba2+ and TEA occur through different pathways in the rat liver.

The role of K+ channels in bile acid-independent bile flow (BAIF) was studied in the isolated and bile duct-cannulated perfused rat liver by changing the driving force on K+ and by using a variety of K+ channel blockers. Bile flow rate, effluent perfusate K+ content, and portal pressure were measured. Increase in perfusate K+ from 5.9 to 80 mM caused inhibition of bile flow that could be fitted to a Boltzmann distribution, indicating partial dependence of bile formation on the K+ equilibrium potential and hence K+ channel activity. To investigate this further, the effects of compounds established as K+ channel blockers in liver or other tissues were surveyed. Ba2+ (1-5 mM) inhibited mean bile flow by 20%. Tetraethylammonium (TEA) inhibition of basal bile flow was biphasic with saturable (IC50 approximately 0.7 mM) and linear components. In contrast, infusion of the K+ channel blockers 4-aminopyridine (5 mM), cesium (2.5 mM), quinidine (0.1 mM), iberiotoxin (90 nM), or paxilline (100 nM) did not affect bile flow. As expected for a K+ channel blocker, Ba2+ caused a net K+ uptake. Conversely, TEA did not affect basal K+ fluxes, although TEA-induced cholestasis was accompanied by a 26% decrease in biliary glutathione excretion. These results suggest that the partial cholestasis induced by the K+ channel blockers Ba2+ and TEA occurs by significantly different mechanisms. Whereas the Ba2+ response implicates K+ channel activity as a significant driving force in BAIF, TEA-sensitive K+ channels are not present or are not involved in bile formation.

Effect of phloracetophenone on bile flow and biliary lipids in rats

Phloracetophenone is the aglycone part of phloracetophenone glucoside, a naturally-occurring compound from the indigenous plant, Curcuma comosa. The glucoside has previously been identified as the choleretic principle of the plant. In the present study, the effects of synthetic phloracetophenone (2,4,6-trihydroxyacetophenone (THA)) on bile flow and biliary lipid secretion were investigated in male rats, using a bile fistula. A single intraduodenal administration of THA at doses of 10–150 mg kg −1 induced a dose-dependent increase in bile flow rate. The increase in bile flow was associated with increased biliary secretion of bile acid, decreased secretion of cholesterol and phospholipid, and lowered bile lithogenic index. THA at a dose of 100 mg kg b.w. −1 induced a maximal increase of bile flow rate (up to 233.8±6.5% of pre-THA control) and bile acid output (up to 293.4±15.2% of pre-THA control). The stimulation of bile secretion by THA was due to an increase in both bile acid-dependent and bile acid-independent flow. A considerable decrease in plasma cholesterol was also observed, which was attributed to the great choleretic activity with enhancement of biliary bile acid secretion. These findings suggest that THA may have potential for development as a therapeutic agent for treatment of cholestasis, dissolving gallstones, and reducing plasma cholesterol.