Formation of lipoprotein-X. Its relationship to bile compounds.

In this study we have demonstrated that in native bile, lipids are organized in the form of a lipoprotein (bile LP) carrying albumin as apoprotein. The lipid composition of bile LP is almost identical to lipoprotein-X (LP-X, the characteristic lipoprotein of cholestasis). However, it differs from LP-X inits protein/lipid ratio and immunological and electrophoretic characteristics. Bile lipoprotein can be converted into "LP-X-like" material in vitro by adding albumin or serum to native bile. The LP-X-like material formed in vitro has physicochemical and chemical characteristics similar or identical to LP-X isolated from serum. As bile lipoprotein can be converted into LP-X-like material by the addition of albumin to bile, LP-X can be converted into bile-LP-like particles by adding bile salts to a LP-X-positive serum. Furthermore, experimental connection of the common bile duct to the vena cava is followed after a few hours by the appearance of LP-X-like material in the plasma. These facts taken together strongly suggest that bile LP is a precursor lipoprotein for LP-X and that it refluxes into the plasma pool under cholestatic conditions.     

Plasma alkaline phosphodiesterase I in intrahepatic cholestasis induced by alpha-naphthylisothiocyanate in rats

1. Administration of alpha-naphthylisothiocyanate (ANIT) to rats produced dose-dependent increases in plasma bile acid and bilirubin concentrations. Similar increases in plasma bile acid and bilirubin concentrations were evident in bile duct ligated rats, indicating that the severity of cholestasis is almost identical in both models. 2. Plasma alkaline phosphodiesterase I was increased by only 50-80% while alkaline phosphatase was increased more than threefold after ANIT administration. This is in contrast to an earlier study [S. R. Simpson, K. Rahman & D. Billington (1984) Clinical Science 67, 647-652] where, after bile duct ligation, serum alkaline phosphodiesterase I was elevated sixfold before any increase in alkaline phosphatase activity became apparent. Thus, plasma alkaline phosphodiesterase I does not offer as sensitive a marker of intrahepatic cholestasis (induced by ANIT) as it does of extrahepatic cholestasis (induced by bile duct ligation). 3. Hepatic alkaline phosphodiesterase I was unaffected by ANIT pretreatment while hepatic alkaline phosphatase was increased up to seven times. It is suggested that raised plasma alkaline phosphodiesterase I is due to regurgitation of the biliary enzyme rather than overspill of the enzyme from liver into blood. 4. Gel filtration showed that 24 h and 96 h after ANIT administration, rat serum contained a high molecular weight form of alkaline phosphodiesterase I, suggesting a different isoenzyme profile.     

Characteristics of hepatic excretory function during development.

The purpose of this investigation was to characterize the development of hepatic excretory function in rats. Cumulative (40 min) intestinal ouabain content was lower and plasma ouabain concentrations were higher in 15-day-old rats than in 21-, 25-, 35- and 45-day-old animals and reached adult levels when rats were 35 days old. Impaired transport of ouabain in rat neonates correlated to low initial ouabain concentration in liver, which suggested that the inability of young rats to accumulate ouabain in liver may be the most important determinant for functional insufficiency. Bile duct ligation and bile salt infusion, treatments that primarily depress and enhance (respectively) excretion of sulfobromophthalein from liver into bile, markedly altered the disappearance of sulfobromophthalein from plasma of adult rats but did not appreciably affect sulfobromophthalein disappearance from blood of 15-day-old rats. The effect of bile duct ligation on ouabain transport in 15-day-old rats was also not as dramatic as the effect produced in adult rats. Hepatic uptake is rapid in adult rats and overall excretion is limited by a slower rate of transport from liver into bile. The lower rate of uptake in 15-day-old rats may limit overall transport function in young animals.     

Alteration of Bile Canalicular Enzymes in Cholestasis. A POSSIBLE CAUSE OF BILE SECRETORY FAILURE

Bile secretory failure (cholestasis) may result from several possible mechanisms involved in bile secretion. We have examined the possibility that abnormalities in enzyme content, composition, and turnover of liver plasma membrane constituents are altered in cholestasis.Severe and mild cholestasis were produced by 5 days of bile duct ligation and ethinyl estradiol administration, respectively. Bile duct ligation but not ethinyl estradiol treatments was associated with elevations of the serum bilirubin level and 5'-nucleotidase activity. However, basal bile flow and bilirubin transport maximum (T(m)) were significantly reduced after ethinyl estradiol treatment. Liver plasma membrane fractions rich in canalicular membranes were prepared from groups of rats in each of three categories; normal, after bile duct ligation, or ethinyl estradiol administration, and their respective controls. Electron microscopy and enzyme marker studies demonstrated plasma membrane fractions free of significant contamination.Plasma membrane fractions prepared from mild as well as severe cholestasis had increased alkaline phosphatase activity, and reduced 5'-nucleotidase and Mg(2+)-ATPase activities. Co(2+)-CMPase activity was unchanged. Kinetic analysis of 5'-nucleotidase and Mg(2+)-ATPase activities in plasma membrane fractions demonstrated reduced V(maz) (but unaltered K(m)). Reducted V(maz) was unrelated to addition in vitro of di-or trihydroxy bile salts or ethinyl estradiol and, therefore, suggests that reduced activities in cholestasis are due to decreased enzyme content. Cholestasis was not associated with changes in the synthesis or degradation rate of pulse-labeled plasma membrane proteins or alterations in the major protein bands separated on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.Plasma membrane cholesterol, phospholipid, and neutral sugar content was unaltered, but sialic acid content was significantly increased in both forms of cholestasis. Alterations in specific canalicular enzymes in two forms of cholestasis suggest that these changes may be involved in the pathogenesis of bile secretory failure, or may result from cholestasis.     

Role of lipoprotein-X in the pathogenesis of cholestatic hypercholesterolemia. Uptake of lipoprotein-X and its effect on 3-hydroxy-3-methylglutaryl coenzyme A reductase and chylomicron remnant removal in human fibroblasts, lymphocytes, and in the rat.

Cholestasis is accompanied by the appearance of lipoprotein-X (LP-X) in plasma. This lipoprotein has a high content of unesterified cholesterol and phospholipids and appears to be ineffective in suppressing the enhanced hepatic cholesterogenesis of cholestasis. Its role as a possible causative factor for cholestatic hypercholesterolemia was investigated. When 125I-LP-X was injected into rats, it disappeared rapidly from the circulation. Calculated on the basis of gram wet weight, spleen took up more LP-X than liver. Prior ligation of the bile duct reduced the uptake in spleen. Experiments with isolated perfused rat liver showed that nonparenchymal cells (NPC) took up over eightfold more 125I-LP-X than hepatic parenchymal cells (PC). Incubation of PC, NPC, human lymphocyte suspensions, or fibroblast cultures with LP-X showed that NPC bound more LP-X than PC or fibroblasts. Lymphocytes took up 20-fold more LP-X than PC and the activity of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase was depressed by LP-X. Lymphocytes isolated from cholestatic patients showed low activity of this enzyme. The activity was increased by LP-X in isolated perfused livers, but suppressed in isolated microsomes. LP-X competitively inhibited the uptake of chylomicron remnants in isolated perfused livers and hepatocytes. In contrast, degradation of LDL by perfused livers, which were isolated from ethinyl estradiol-treated rats or human fibroblast cultures, remained unchanged in the presence of LP-X. The results indicate that cholesterol transported by LP-X is mainly taken up by the cells of the reticuloendothelial system. It increases the activity of hepatic HMG-CoA reductase and suppresses remnant uptake, thus emphasizing a major role of LP-X in cholestatic hypercholesterolemia.     

Effects of chronic nitric oxide activation or inhibition on early hepatic fibrosis in rats with bile duct ligation

Hepatic fibrosis or increased liver collagen contents drive functional abnormalities that, when extensive, may be life threatening. The purpose of this study was to assess the effects of the chronic stimulation or inhibition of nitric oxide synthesis in rats with hepatic fibrosis induced by permanent common bile duct ligation (3 weeks) and the role of expression of the different nitric oxide synthase isoforms. Bile duct ligation led to an important accumulation of collagen in the hepatic parenchyma, as shown both histologically and by the hydroxyproline contents of livers. Bilirubin and serum enzyme activities (measured as markers of cholestasis) increased several-fold after bile duct ligation. The area of fibrotic tissue, liver hydroxyproline content and serum markers of cholestasis were clearly related in obstructed rats. The absence of modifications in haemodynamic parameters excludes circulatory changes from being responsible for the development of liver alterations. In animals treated with NG-nitro-L-arginine methyl ester (L-NAME) the area of fibrosis was similar to that of untreated animals, the signs of cholestasis and cellular injury being more evident. In rats treated with L-arginine the area of fibrosis was almost three times larger than that found in bile duct ligated rats and in L-NAME-treated bile duct ligated rats, although the observed biochemical changes were similar to those seen in rats treated with L-NAME. Our results with inducible nitric oxide synthase, obtained by Western blots and immunohistochemistry, indicate a greater expression of the inducible enzyme in bile duct ligated and L-arginine-treated animals and a lower expression in the L-NAME and control groups. Constitutive nitric oxide synthase expression, obtained by Western blots, was very similar in all groups, except for the L-arginine-treated rats in which it was lower. These results suggest that nitric oxide production may be a key factor in the development of fibrosis in bile duct ligated rats. They also support the hypothesis of a dual role for nitric oxide; one beneficial, mediated by its circulatory effects, and the second negative, through its local toxic effects.     

Changes in rat serum lipoproteins following ligation of the bile duct.

Lipoproteins in the serum of normal and of cholestatic rats have been studied by crossed immunoelectrophoresis coupled with separations by rate and isopycnic density gradient centrifugation and by gel exclusion chromatography. Normal rat serum contained distinct lipoprotein species closely analogous to human VLDL, LDL, HDL2 and HDL3. Three days after ligation of the common bile duct, there were major changes in the lipoproteins of rat serum. The amounts of VLDL, LDL and of a minor HDL component were elevated and several novel types of lipoprotein were detected. Three of these could be identified as the characteristic lipoprotein of cholestasis, LP-X, as an enlarged and modified HDL and as a lipoprotein of density 1.055 g/ml intermediate in size between LDL and VLDL. Some unusually small VLDL particles were also detected. It is concluded that the changes in rat serum lipoproteins following ligation of the common bile duct are very similar to the changes observed in cholestatic disease in human patients.     

Lecithin.cholesterol acyl-transferase and lipoprotein-X in liver disease

Determinations of serum lecithin : cholesterol acyl transferase (LCAT) and the “abnormal serum lipoprotein of cholestasis” (LP-X) have been carried out in 52 patients with different liver disorders and in 20 normal subjects.In acute hepatitis reduced LCAT activity was demonstrated in both LP-X positive and LP-X negative patients. In primary biliary cirrhosis and large bile duct obstruction the presence of LP-X was associated with reduced, normal or increased LCAT activity. Thus this study could reveal no specific LCAT/LP-X pattern in liver diseases, nor were we able to differentiate between intra- and extrahepatic cholestasis on the basis of these two tests.Possible relationships between LP-X and LCAT are discussed and mechanisms for the formation of LP-X in liver- and bile duct diseases are considered.     

Enzyme changes and morphometric analysis of bile ducts in experimental bile duct obstruction.

Chronic bile duct obstruction causes a marked proliferation of bile ductules within the rat liver plus an increase in the activities of hepatic gamma-glutamyl transpeptidase, 5'-nucleotidase and alkaline phosphatase. To determine if the increase in the activities of these enzymes within the liver simply reflects the increase in bile duct mass, we subjected rats to bile duct ligation for periods up to one week and compared the activities of these enzymes within liver tissue with bile duct volume, determined by morphometric analysis. The activities of two enzymes not useful in the diagnosis of chronic cholestasis, aspartate aminotransferase (GOT) and alanine aminotransferase (GPT), were also measured. There was no correlation between the proliferation of bile ductules and the activity of any of these enzymes. Bile duct volume increased 4.9-fold within 24 h after ligation and rose steadily, reaching a value of 13 times control in one week. Alkaline phosphatase activity increased 3.6-fold within 24 h after bile duct ligation and then was relatively constant. Gamma-glutamyl transpeptidase and 5'-nucleotidase activity both fell 24 h after ligation but were slightly increased after 48 h. Enzyme activities of each were almost twice control at 120 and 168 h. Alanine aminotransferase activity fell steadily during the period of bile duct ligation, while aspartate aminotransferase was unchanged. The change in gamma-glutamyl transpeptidase and 5'-nucleotidase activity within the liver cannot be due simply to hypertrophy of bile duct epithelium.     

Critical role of plasminogen activator inhibitor-1 in cholestatic liver injury and fibrosis

Plasminogen activator inhibitor-1 (PAI-1) is an acute phase protein known to correlate with hepatic fibrosis. However, whether or not PAI-1 plays a causal role in this disease process had not been directly tested. Therefore, wild-type or PAI-1 knockout (PAI-1(-/-)) mice underwent bile duct ligation. Mice were sacrificed either 3 or 14 days after surgery for assessment of early (i.e., inflammation) and late (i.e., fibrosis) changes caused by bile duct ligation. Liver injury was determined by histopathology and plasma enzymes. Accumulation of extracellular matrix was evaluated by Sirius red staining and by measuring hydroxyproline content. Hepatic expression of PAI-1 was increased approximately 9-fold by bile duct ligation in wild-type mice. Furthermore, early liver injury and inflammation due to bile duct ligation was significantly blunted in PAI-1(-/-) mice in comparison with wild-type mice. Although PAI-1(-/-) mice were significantly protected against the accumulation of extracellular matrix caused by bile duct ligation, increases in expression of indices of stellate cell activation and collagen synthesis caused by bile duct ligation were not attenuated. Protection did, however, correlate with an elevation in hepatic activities of plasminogen activator and matrix metalloprotease activities. In contrast, the increase in tissue inhibitor of metalloproteases-1 protein, a major inhibitor of matrix metalloproteases, caused by bile duct ligation was not altered in PAI-1(-/-) mice compared with the wild-type strain. The increase in hepatic activity of urokinase-type plasminogen activator was also accompanied by more activation of the hepatocyte growth factor receptor c-Met. Taken together, these data suggest that PAI-1 plays a causal role in mediating fibrosis during cholestasis.     

Importance of renal prostaglandins in control of renal function after chronic ligation of the common bile duct in dogs

To explore the possible vasoregulatory role of renal prostaglandins during liver disease, excretory rates of PGE2, PGF2 alpha, and a metabolite of PGI2, 6k-PGF1 alpha, were determined before and after chronic ligation of the common bile duct in 23 dogs. Bile duct ligation for 50 +/- 3.7 days (mean +/- SEM) significantly increased serum bilirubin and alkaline phosphatase. PGE2, PGF2 alpha, and 6k-PGF1 alpha excretion rates were significantly (p less than 0.01) increased following chronic bile duct ligation, by approximately 100%, 80%, and 500%, respectively, with similar increments in both ascitic and nonascitic animals. In 10 sham-ligated animals, PGE2, PGF2 alpha, and 6k-PGF1 alpha excretion rates were unchanged. In 6 dogs sequential measurements of urine prostaglandins indicated that PGE2 and 6k-PGF1 alpha excretion were significantly increased at 2, 4, and 6 weeks after ligation, whereas the increase in PGF2 alpha excretion was not significant until 6 weeks. Indomethacin (2 mg/kg) reduced prostaglandin excretion by 65% to 90% and significantly increased arterial pressure, decreased glomerular filtration rate and renal blood flow, and increased renal vascular resistance from 0.53 +/- 0.09 to 0.90 +/- 0.13 mm Hg/ml/min. Fractional renal blood flow, assessed by microspheres, was disproportionately reduced in the inner cortex after prostaglandin inhibition in the chronic bile duct ligation group. Indomethacin did not significantly alter renal function in sham animals, despite comparable reductions in prostaglandin excretion. These data demonstrate that, in dogs with experimental liver disease produced by chronic bile duct ligation, renal prostaglandin synthesis is increased, and the enhanced synthesis of vasodilatory prostaglandins serves to maintain renal blood flow and glomerular filtration rate.     

Effect of cholestasis on hepatic transport of 99mtechnetium p-isopropyl-iminodiacetic acid

Hepatobiliary imaging with 99mTc-p-isopropyl-iminodiacetic acid (PIPIDA) and other acetanilidoiminodiacetic acid derivatives is a frequently used clinical tool in evaluating patients with jaundice. However, there has been little objective assessment of the effects of cholestasis on hepatic transport of acetanilioiminodiacetic acid derivatives. In our studies, transport of 99mTc-PIPIDA by isolated rat hepatocytes obtained from animals with extrahepatic obstruction secondary to bile duct ligation or intrahepatic cholestasis induced by ethinyl estradiol therapy was determined. Uptake constants for 99mTc-PIPIDA by hepatocytes isolated from livers of animals with ligated bile ducts were significantly decreased compared with uptake by liver cells from sham-operated controls (0.0030 +/- 0.0003 vs. 0.0089 +/- 0.0010 femtomole X 10(6) cells-1 X min-1 X pmol/L-1; p less than 0.001). Hepatocytes isolated from livers of animals given ethinyl estradiol also demonstrated significantly reduced 99mTc-PIPIDA uptake compared with controls given propylene glycol (0.0034 +/- 0.0002 vs. 0.0060 +/- 0.0004 fmol X 10(6) cells-1 X min-1 X pmol/L-1; p less than 0.001). Fractional rates of efflux of the study compound from hepatocytes preincubated with 99mTc-PIPIDA were significantly decreased in experiments using ethinyl estradiol (p less than 0.005) but did not differ significantly from controls in studies of bile duct ligation. 99mTc-PIPIDA uptake was significantly decreased in the presence of high bile salt concentrations (100 to 200 mumol/L), but unconjugated bilirubin concentrations as high as 200 mumol/L (approximately 12 mg/dl) had no effect on hepatocyte uptake of the ligand. The finding that cholestasis significantly impairs hepatocyte uptake of 99mTc-PIPIDA provides a possible explanation for the clinical observation that a patent biliary tree and normal serum bilirubin level are not always sufficient to ensure normal hepatobiliary imaging. These data also suggest that elevation of bile acid levels during cholestasis may either contribute to impaired uptake of hepatobiliary imaging agents or serve as a marker of cholestasis-induced abnormalities in the liver functions responsible for hepatic transport of these compounds.     

Class III P-glycoproteins mediate the formation of lipoprotein X in the mouse.

Cholestasis is associated with hypercholesterolemia and appearance of the abnormal lipoprotein X (LpX) in plasma. Using mice with a disrupted Mdr2 gene, we tested the hypothesis that LpX originates as a biliary lipid vesicle. Mdr2-deficient mice lack Mdr2 P-glycoprotein, the canalicular translocator for phosphatidylcholine, and secrete virtually no phospholipid and cholesterol in bile. Bile duct ligation of Mdr2(+)/+ mice induced a dramatic increase in the plasma cholesterol and phospholipid concentration. Agarose electrophoresis, density gradient ultracentrifugation, gel permeation, and electron microscopy revealed that the majority of phospholipid and cholesterol was present as LpX, a 40-100 nm vesicle with an aqueous lumen. In contrast, the plasma cholesterol and phospholipid concentration in Mdr2(-)/- mice decreased upon bile duct ligation, and plasma fractionation revealed a complete absence of LpX. In mice with various expression levels of Mdr2 or MDR3, the human homolog of Mdr2, we observed that the plasma level of cholesterol and phospholipid during cholestasis correlated very closely with the expression level of these canalicular P-glycoproteins. These data demonstrate that during cholestasis there is a quantitative shift of lipid secretion from bile to the plasma compartment in the form of LpX. The concentration of this lipoprotein is determined by the activity of the canalicular phospholipid translocator.     

Enhancement of aspirin-induced gastric damage by cholestasis in rats

Summary— In this study the seventy of aspirin-induced gastric mucosal damage was investigated in rats with obstructive cholestasis. Cholestasis was induced by ligation and resection of the bile duct under general anesthesia. Two weeks after operation, the rats were fasted for 24 hours. Aspirin was administered orally in doses of 0, 128, 192, 266 and 335 mg/kg, and the animals were killed four hours after dosing. The dose of 266 mg/kg was chosen for a study of the time-dependency; other groups of animals were killed at time intervals of one, three, five, seven and nine hours after aspirin administration. The results showed that aspirin induces more severe gastric damage in bile duct resected rats compared with sham-operated and control animals. Salicylate levels of serums were also measured but there was no significant difference in serum salicylate levels between bile duct resected, sham-operated and control rats. It can be concluded that cholestasis can potentiate aspirin-induced gastric damage in rats.     

Quantitative changes of serum lipoprotein-X after cholestyramine administration in infants with cholestatic biliary tract and liver disease

Lipoprotein-X (LP-X) was determined before and after the administration of cholestyramine in fifty-five infants with persistent cholestatic jaundice to differentiate between intra- and extrahepatic disease. In twenty-seven infants with biliary atresia, serum LP-X prior to cholestyramine ranged from 0.87 to 11.42 g/l (mean: 3.43 g/l; the average concentration was significantly lower (P less than 0.001) in males. After cholestyramine, LP-X rose in twenty-three, remained the same in two, and decreased slightly in two infants. Serum LP-X was present in twenty of the twenty-eight infants with intrahepatic cholestasis prior to cholestyramine in concentrations from 0.84 to 14.19 g/l (mean: 3.13 g/l). After cholestyramine, LP-X decreased in all by an average of 78% (P less than 0.005). The other eight infants did not have LP-X before or after cholestyramine. This study shows that LP-X in the serum of infants with cholestatic jaundice indicates severe cholestasis, but is not itself diagnostic of biliary atresia. The differentiation of biliary atresia from other diseases is readily achieved, as the administration of cholestyramine for 2-3 weeks causes a marked decrease of serum LP-X in patients with patent extrahepatic bile ducts. The absence of serum LP-X excludes biliary atresia.     

Chronic biliary obstruction induces pulmonary intravascular phagocytosis and endotoxin sensitivity in rats.

Endotoxin sensitivity varies among animal species and appears to correlate with the presence of pulmonary intravascular macrophage (PIM). In rats, which lack PIM, we investigated the hypothesis that chronic cholestatic liver injury leads to induction of PIM and endotoxin sensitivity. Rats were randomized to either common bile duct ligation (BDL) or sham-surgery and studied at 1 wk (acute cholestasis), 2 wk (cholestasis, early cirrhosis), and 4 wk (cholestasis, established cirrhosis) after surgery. Intravascularly injected fluorescent latex microspheres (1 micron diameter) were taken up by large phagocytic cells in lung parenchyma of BDL rats (at 2 and 4 wk), while no uptake was observed in lungs from control rats. Electronmicroscopy revealed accumulation of large, mononuclear, macrophage-like cells containing ingested latex particles within the pulmonary capillaries. Pulmonary intravascular phagocytosis, as reflected in lung uptake of 99mTc microaggregated albumin (Microlite, mean particle diameter = 1 micron), averaged 0.7 +/- 0.1% (mean +/- SEM) of total injected dose in 13 control rats and progressively increased with time after BDL (1 wk, 1.7 +/- 0.2%; 2 wk, 10.0 +/- 3.0%; 4 wk 35.1 +/- 5.9%). Rats with biliary cirrhosis were markedly sensitive to the lethal effects of low dose endotoxin and demonstrated marked lung edema at the time of death. Furthermore, the lung uptake of intravascular 125I-lipopolysaccharide was increased five-fold in cirrhotic rats. We conclude that chronic biliary obstruction leads to the induction of pulmonary intravascular phagocytes and enhances endotoxin sensitivity in rats. Pulmonary intravascular phagocytosis in patients with advanced cirrhosis may account for their increased susceptibility to sepsis-induced adult respiratory distress syndrome.     

Viral gene delivery of superoxide dismutase attenuates experimental cholestasis-induced liver fibrosis in the rat

Hydrophobic bile acids lead to generation of oxygen free radicals in mitochondria. Accordingly, this study investigated if gene delivery of superoxide dismutase (SOD) would reduce hepatic injury caused by experimental cholestasis. Rats were given adenovirus (Ad; 3 x 10(9) p.f.u., i.v.) carrying the bacterial control gene lacZ, mitochondrial Mn-SOD or cytosolic Cu/Zn-SOD genes 3 days before bile duct ligation. Both Mn- and Cu/Zn-SOD activity was increased in the liver about four-fold 3 days after viral infection. Serum alanine transaminase increased to about 710 U/l after bile duct ligation, which was blunted by about 70% in rats receiving Ad-Mn-SOD, but by only 30% in rats receiving Ad-Cu/Zn-SOD. Bile duct ligation caused focal necrosis, apoptosis and fibrosis in the liver and increased collagen alpha1 mRNA about 20-fold. These effects were reduced significantly by Ad-Mn-SOD, but not by Ad-Cu/Zn-SOD. In addition, bile duct ligation increased 4-hydroxynonenal, a product of lipid peroxidation, activated NF-kappaB and increased synthesis of TNF(alpha) and TGF-beta. These effects were also blunted significantly by Ad-Mn-SOD, but not by Ad-Cu/Zn-SOD. Taken together, it is concluded that cholestasis causes liver injury by mechanisms involving mitochondrial oxidative stress. Gene delivery of mitochondrial Mn-SOD blocks formation of oxygen radicals and production of toxic cytokines thereby minimizing liver injury caused by cholestasis.     

Biliary levels of ceforanide.

Ceforanide levels in plasma, gallbladder bile, gallbladder tissue, and common bile duct were studied in 10 patients with normal biliary tracts and in 35 patients with biliary disease at various intervals after intravenous injection of 1 g of the drug. Peak blood levels were obtained within 1 h of administration (mean, 67 +/- 15 micrograms/ml). Patients with a normal bilary tract, as well as patients with chronic cholecystitis and a patent cystic duct, achieved high gallbladder bile levels of ceforanide within 2 h (mean, 76 +/- 25 micrograms/ml) and attained even higher levels by 4 h (mean, 182 +/- 51 micrograms/ml). However, all patients with chronic cholecystitis and an occluded cystic duct had very low drug concentrations in the gallbladder bile (14 +/- 7 micrograms/ml at 2 h). Despite this difference in gallbladder bile levels, ceforanide levels of 21 +/- 3 micrograms/g were achieved at 1 to 3 h in gallbladder tissue in both groups with chronic cholecystitis. The concentration of ceforanide in common bile duct was 149 +/- 59 micrograms/ml at 2 h after administration, with levels over 60 micrograms/ml present from 1 to 4 h after administration. These results indicate that ceforanide reaches high levels in the biliary tract. Its potential value in the prevention and treatment of biliary infections should be assessed.     

Lack of detrimental effects of nitric oxide inhibition in bile duct-ligated rats with hepatic encephalopathy

BACKGROUND: The pathogenetic mechanisms of hepatic encephalopathy (HE) are not fully understood. Vasodilatation induced by nitric oxide (NO) may be involved in the development of HE. There is no comprehensive data concerning the effects of NO inhibition on HE in chronic liver disease. METHODS: Male Sprague-Dawley rats weighing 240-270 g at the time of surgery were selected for experiments. Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Counts of movements were compared between BDL rats and rats receiving a sham operation. In another series of experiments, BDL rats received either Nomega-nitro-L-arginine methyl ester (L-NAME, 25 mg kg-1 day-1 in tap water) or tap water (control) from the 36th to 42nd days after BDL. Besides motor activities, plasma levels of tumour necrosis factor (TNF)-alpha and nitrate/nitrite, liver biochemistry tests and haemodynamics were determined after treatment. RESULTS: Compared with the sham-operated rats, the total, ambulatory and vertical movements were significantly decreased in the BDL rats (P 相似文献   

Cholestatic effect of carmustine in rats

A single i.p. dose of 20 mg/kg of carmustine [1,3-bis-(2-chloroethyl)-1-nitrosourea; BCNU] caused intrahepatic cholestasis in rats within 48 hr of administration. Cholestasis was characterized by a selective reduction of the bile salt independent fraction of bile flow. Increased plasma K+ and decreased plasma Na+ concentrations, consistent with this effect, were observed. Because bile: plasma osmolality and biliary bile salt concentrations were elevated, increased permeability to bile salts and other osmotically active solutes between bile and plasma is unlikely. Bile salt excretion was normal despite the reduced bile flow because biliary bile salt concentration was increased. In contrast, the treated rats were unable to concentrate bromosulfophthalein in bile before, during and after the onset of cholestasis. Because no reduction in hepatic perfusion was observed in vivo in BCNU-treated rats, reduced xenobiotic organic anion excretion may be a selective effect of the drug. The cholestatic effects of BCNU appear to be different from either alpha-naphthylisothiocyanate or estrogenic steroids.