The role of proliferation in the origin of mutations in mammalian cells

Biliary obstruction, produced by common bile duct ligation or alpha-naphthylisothiocyanate (ANIT) treatment in rats, has been associated with the development of type I biliary epithelial cell (BEC) hyperplasia. However, the exact mechanism(s) by which bile duct obstruction lead(s) to this proliferative lesion are not clear. The present studies were designed to determine if cholestasis, in the absence of biliary obstruction, would result in type I BEC hyperplasia. Male Sprague-Dawley rats were given a single oral dose of 150 mg/kg ANIT or i.v. doses of estradiol glucuronide (E2-17G; 21 mumol/kg/h for 48 h) to produce obstructive and non-obstructive cholestasis, respectively. E2-17G treatment resulted in cholestasis that was comparable in extent and duration to that observed following ANIT treatment. E2-17G and ANIT treatments produced comparable increases in serum bile acids (55- to 60-fold) and activities of ALT (36- to 38-fold), ALP (4- to 5-fold), and 5'-nucleotidase (7- to 11-fold), respectively, compared to controls. Both ANIT and E2-17G also increased serum bilirubin concentrations. ANIT treatment resulted in significant increases in biliary glucose concentrations that were associated with BEC damage/necrosis and obstruction of the bile duct lumen. Conversely, no evidence of BEC damage was observed in E2-17G-treated rats. Nonetheless, BEC hyperplasia was observed in the majority of rats following treatment with either ANIT or E2-17G, assessed by light microscopy and by BrdU immunohistochemistry. These data indicate that E2-17G treatment produces nonobstructive cholestasis and type I BEC hyperplasia, suggesting that biliary obstruction is not a prerequisite for type I BEC hyperplasia in rats. Differences in the time of onset of hyperplasia were observed: hyperplasia was noted immediately following 48 h of E2-17G-induced cholestasis but occurred several days after ANIT-induced cholestasis had subsided. Since the magnitude/duration of cholestasis was similar in the two models but the temporal association between cholestasis and type I BEC hyperplasia were different, these data suggest that the proliferative stimulus may be different in the two models and that E2-17G-induced type I BEC hyperplasia may not be attributed solely to cholestasis.     

A longitudinal study of circulating lymphocyte subsets in the peripheral blood during the acute stage of Guillain-Barré syndrome

We investigated sequential changes in bile flow, serum and biliary biochemical parameters in phalloidin-induced cholestasis in rats. Intrahepatic cholestasis was induced by administration with phalloidin (500 microg/kg) for 7 days, and then the animals were allowed to survive for 1, 2, 4, 7, 14 and 28 days after the last treatment. In phalloidin-treated rats, bile flow significantly decreased up to 4 days of recovery, compared with the control animals. In contrast, serum ALP activity, LAP activity, cholesterol concentration and phospholipid concentration exhibited a marked elevation throughout the recovery periods. For biliary parameters, bilirubin excretion rate was unchanged but, cholesterol excretion rate showed a marked decrease throughout the recovery periods. These results demonstrate that some parameters, particularly important indexes of cholestasis (serum ALP, cholesterol, bile flow and so on), continued significant changes at least 4 days after the last administration of phalloidin. These results demonstrate that successive treatment with phalloidin can cause damage in most of serum and biliary parameters at a chronic stage of cholestasis. Thus, our findings may provide useful information for diagnosis of drug-induced cholestasis and help to further elucidate the biochemical mechanisms of drug-induced cholestasis in humans.     

Effect of bile duct ligation on bile acid metabolism in rats

The effect of bile duct ligation on the quantitative and qualitative changes of bile acids in serum, liver, urine, and feces, and the concentration of cholesterol and phospholipids in serum and liver were examined in male rats. The concentration of bile acids in serum increased over 100-fold on day 5 but was lower than the 5-day level on days 10 and 15. The concentration in the liver also increased about 10-fold. beta-Muricholic acid predominantly increased but the secondary bile acids, deoxycholic acid and hyodeoxycholic acid, decreased. The urinary excretion of bile acids increased to about 40 mg/day per rat on the first day of bile duct ligation but this increase was reduced on day 2 to about half and remained at that level until day 24. These values exceeded that of fecal bile acids, 12 mg/day per rat, before bile duct ligation. The amount of bile acid sulfates in the urine was as low as 1% of the total. The urinary non-sulfated bile acids consisted mainly of beta-muricholic acid (60%) and cholic acid (20%), while the sulfates contained a considerable amount of unidentified acidic substances (40%) in addition to cholic acid and beta-muricholic acid. The concentration of cholesterol and phospholipids in serum markedly increased on day 5 but declined gradually thereafter. The liver cholesterol concentration did not change but the phospholipid concentration decreased. Fecal sterols did not change in both the total amount and composition. These data indicated that daily synthesis of bile acids, especially beta-muricholic acid, was accelerated in bile duct-ligated rats.     

Potential for cross-contamination from use of a needleless injector

In this study the severity 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.     

Hepatoprotection in ethinylestradiol-treated rats is provided by tauroursodeoxycholic acid, but not by ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) have been suggested as potential treatments for drug-induced cholestasis. It was therefore decided to study the effects of administration of UDCA or TUDCA on individual serum bile acid concentration, conventional liver tests and associated hepatic ultrastructural changes in ethinylestradiol-treated (EE) rats mg/kg per day). Control rats were treated s.c. with propylene glycol. EE-treated rats were randomly assigned to receive daily i.p. injections of placebo, TUDCA or UDCA. Four rats in each group were treated for 4 consecutive days, and a second four for 14 days. After 4 days of treatment, the serum levels of cholic acid and taurocholic acid were significantly increased in EE-treated rats. None of the conventional liver tests were significantly different among the four groups. After 14 days of treatment the serum levels of cholic acid, chenodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, bilirubin, alkaline phosphatase and gamma glutamyltransferase were significantly raised in EE and EE plus UDCA treated rats. EE plus TUDCA treated rats, however, had no significant changes in these individual serum bile acids or conventional liver tests. The ultrastructure of livers from EE plus TUDCA treated rats was similar to those of controls. On the other hand, EE and EE plus UDCA rats both showed a significant reduction in sinusoidal microvilli. These results show that treatment of rats for 4 days with EE induces significant rises in the serum concentrations of two individual bile acids and that TUDCA protects against this.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reversibility of hepatic mitochondrial damage in rats with long-term cholestasis

BACKGROUND/AIMS: Long-term bile duct ligation in rats is associated with secondary biliary cirrhosis and metabolic alterations, e.g. mitochondrial dysfunction. We performed the current studies to characterize the reversibility of hepatic mitochondrial dysfunction after reversing biliary obstruction by Roux-en-Y anastomosis. METHODS: Rats were studied after 4 weeks of bile duct ligation, and after 5 or 14 days of reanastomosis. Control rats were pair-fed to treated rats and all rats were studied after starvation for 24 h. Mitochondria were isolated by differential centrifugation and enzyme activities determined by spectrophotometric methods. RESULTS: In comparison to controls, plasma beta-hydroxybutyrate concentrations were decreased in bile duct ligated rats (200+/-70 vs. 790+/-200 micromol/l) and remained decreased after relief of biliary obstruction. In contrast, plasma free fatty acids were not different between controls and treated rats. Oxidative metabolism of L-glutamate, succinate and duroquinol was decreased in liver mitochondria from bile duct ligated rats. After relief of biliary obstruction, the metabolism of L-glutamate and duroquinol normalized quickly, whereas succinate metabolism remained impaired. Similar results were obtained for the mitochondrial oxidases in disrupted mitochondria. The activities of complex I, II, III and V of the respiratory chain were reduced in bile duct ligated rats. After relief of biliary obstruction, complex I and III normalized quickly, whereas complex II and V remained impaired. Oxidative metabolism of long-chain fatty acids by isolated liver mitochondria was decreased in bile duct ligated rats and did not recover after relief of biliary obstruction. CONCLUSIONS: Long-term cholestasis in the rat is associated with a decrease in specific functions of liver mitochondria which recover only partially after Roux-en-Y anastomosis. The persistence of decreased mitochondrial fatty acid metabolism cannot be explained by impaired activity of the respiratory chain, but is more likely due to alterations in mitochondrial beta-oxidation.     

Mn-DPDP enhanced MRI in experimental bile duct obstruction

To assess both the effect of Mn-DPDP as a hepatobiliary-specific contrast agent in bile duct obstruction and the relative role of liver and kidney in the elimination of this agent from the body, an animal experiment was set up. Twelve rats were used and divided into three groups. In group 1 the common bile duct was ligated, in group 2 bile duct ligation was limited to one lobe, and group 3 served as control. Magnetic resonance T1-weighted SE images were obtained before and after the injection of 25 mumol/kg of Mn-DPDP during the first 2 h and at day 1, 2, 3, 4, and, in some animals, up to 21 days. In normal rats the absolute enhancement signal-to-noise ratio (S/N) versus time plots obtained from the liver after Mn-DPDP injection returned to precontrast values within 24 h. In the group with common bile duct ligation, important liver enhancement persisted up to 21 days. In the group with selective obstruction, liver intensity normalized after 3 days. The S/N plots from spleen, renal cortex, and obstructed liver lobe showed similarities in time course. The present data indicate that Mn elimination is strongly impaired in the presence of bile duct obstruction. Renal glomerular filtration is ineffective in eliminating Mn from the body. The persisting splenic and renal cortical enhancement suggests that free Mn or some Mn-DPDP metabolite either is strongly bound to plasma proteins and acts as a blood pooling agent and/or is uptaken by the splenic or renal parenchyma.     

Liver tissue schistosomiasis mansoni vaccine, as a third generation livestock immunogenes

To assess the effects of cholestasis during pregnancy on fetal and neonatal mRNA expression, protein mass, and function of the Na+/taurocholate cotransporting polypeptide (Ntcp), common bile duct ligation (BDL) was performed in pregnant rats on day 14 of pregnancy (maternal cholestasis [MC] group), and livers were harvested at days 20 and 21 of fetal life, as well as at days 4, 7, 14, 21, and 28 after birth. Sham-operated rats and their litters were used as controls. Ntcp steady-state mRNA levels, protein mass, and function were determined by Northern blotting, immunoblotting, and taurocholate (TC) transport studies in isolated short-term cultured hepatocytes, respectively. In addition, protein mass and function of the organic anion transporting polypeptide (Oatp1), another sinusoidal bile acid transporter, were studied at 4 weeks of age. The majority of pregnant cholestatic rats (94%) were able to carry pregnancy to term. Body and liver weights of the offspring from the MC group were lower than those from sham-operated animals at all postnatal time points. Ntcp steady-state mRNA levels, protein mass, and function were unaffected by MC. The ontogenic pattern of expression was identical in offspring from MC and controls with detection of the Ntcp mRNA at day 21 of fetal life. There was a significant increase in mRNA postnatally, reaching adult levels by 7 days of age. Protein mass and function of Ntcp as well as of Oatp1 were similar in offspring from MC and control groups at 4 weeks of age. In conclusion, maternal obstructive cholestasis during the last third of pregnancy does not affect the fetal/neonatal expression of the basolateral bile acid transporters, Ntcp and Oatp1. This suggests that the impaired bile acid excretion described in this experimental model is not related to altered uptake of bile acids in the affected neonate.     

Alternative reproductive strategies in the ruff, Philomachus pugnax: a mixed ESS?

BACKGROUND/AIMS: Hepatic graft dysfunction is a major management problem in the early post-liver transplantation period. Our aims were to study how liver transplantation per se affects bile formation, and to investigate the role of cyclosporine in the pathogenesis of early graft dysfunction. METHODS: Syngeneic liver transplantation used male Lewis rats. Two weeks after transplantation, the rats were randomly assigned to receive either daily subcutaneous injections of cyclosporine 10 mg/kg for 1 week (n=8), or daily saline injections (Placebo, n=8). 24-h bile collections were performed 18 h after the last injection. Eight non-transplanted rats served as controls. RESULTS: Liver transplantation per se (Placebo) significantly increased basal bile flow (51%), particularly that portion which was bile salt-independent flow (81%), but did not impair bile salt kinetics or biliary lipid composition. Cyclosporine reduced basal bile flow and bile salt-independent flow by 41% and 30%, respectively. Bile salt synthesis was 52% suppressed, leading to a 22% decrease in the bile salt pool size. The recycling frequency of the bile salt pool was unaffected. The drug inhibited bile salt (37%) and phospholipid (23%) outputs; cholesterol secretion remained unaltered. This significantly elevated the cholesterol saturation of bile (25%). CONCLUSIONS: Liver transplantation per se is choleretic and does not impair bile formation or lipid composition in this inbred rat model. Parenteral administration of high-dose cyclosporine induces cholestasis by inhibiting bile salt secretion and BSIF. Bile salt synthesis is down-regulated and the bile salt pool size decreased. The drug adversely affects biliary lipid composition by differential inhibition of bile salt and phospholipid outputs relative to an unchanged cholesterol secretion.     

Elevated levels of bile acids in colostrum of patients with cholestasis of pregnancy are decreased following ursodeoxycholic acid therapy [see comemnts

BACKGROUND/AIMS: Intrahepatic cholestasis of pregnancy is characterised by increased levels of serum bile acids. Ursodeoxycholic acid therapy corrects the serum bile acid profile. The aims of this study were: (i) to investigate bile acid excretion into colostrum of women with intrahepatic cholestasis of pregnancy; (ii) to compare concentrations of bile acids in serum and colostrum of non-treated and ursodeoxycholic acid-treated patients; and (iii) to clarify whether ursodeoxycholic acid is eliminated into colostrum following treatment. METHODS: Bile acids were assessed by gas chromatography and high-performance liquid chromatography in serum collected at delivery, and in colostrum obtained at 2+/-1 days after labour, from patients with intrahepatic cholestasis of pregnancy, non-treated (n=9) and treated (n=7) with ursodeoxycholic acid (14 mg/kg bw per day, for 14+/-7 days) until parturition. RESULTS: The concentration of total bile acids in colostrum from patients with intrahepatic cholestasis of pregnancy was higher than in normals (23.3+/-14.8 micromol/l vs. 0.7+/-0.2 micromol/l, p<0.01) and cholic acid was a major species (19.0+/-13.1 micromol/l), reflecting the elevated concentrations in maternal serum (48.9+/-21.0 micromol/l, total bile acids; 33.9+/-16.7 micromol/l, cholic acid. Following ursodeoxycholic acid administration, total bile acids and cholic acid levels in colostrum diminished to 5.7+/-2.5 micromol/l and 3.6+/-1.5 micromol/l, respectively; the proportion of cholic acid decreased (60.6+/-8.0% vs. 76.8+/-5.0%, p<0.05). The ursodeoxycholic acid concentration in colostrum was maintained following treatment; its increased percentage (9.4+/-3.2% vs. 1.0+/-0.2%, p<0.01) was still lower than in maternal serum (20.8+/-3.6%, p<0.05). Only a small proportion (<1%) of lithocholic acid was found in colostrum following therapy. CONCLUSIONS: Bile acid concentrations are elevated and cholic acid is the major species accumulating in colostrum, reflecting serum bile acid profiles in intrahepatic cholestasis of pregnancy. Ursodeoxycholic acid therapy decreases endogenous bile acid levels in colostrum.     

Vascular hyporesponsiveness in aortic rings from cirrhotic rats: role of nitric oxide and endothelium

1. The role of nitric oxide as mediator of the vascular alterations present in different models of experimental liver cirrhosis is controversial. In the present study, we evaluated the role of nitric oxide and that of the endothelium in the response to phenylephrine and acetylcholine of isolated aortic rings from chronic bile duct-ligated (29 days) rats and their corresponding controls. Experiments were performed in rings with or without endothelium, in rings pretreated with N-omega-nitro-L-arginine methyl ester (10(-4) mol/l) to inhibit nitric oxide synthesis and in rings pretreated with aminoguanidine (10(-4) mol/l) to inhibit inducible nitric oxide synthesis. 2. Under basal conditions, the maximum absolute tension developed in response to cumulative addition of phenylephrine was significantly decreased in rings from bile duct-ligated animals (1.62 +/- 0.06 g) compared with the control rings (2.15 +/- 0.099). This hyporesponsiveness to phenylephrine of rings from bile duct-ligated animals was corrected after treatment with N-omega-nitro-L-arginine methyl ester and reduced, but not completely eliminated, in rings without endothelium. In contrast, aminoguanidine did not modify the lower response to phenylephrine rings from bile duct-ligated animals. ED50 values were not different between groups under any experimental conditions. 3. The endothelium-dependent vasodilatation to acetylcholine in phenylephrine-constricted rings was similar in both groups of animals, control and bile duct ligated, under all experimental conditions. N-omega-nitro-L-arginine methyl ester pretreatment and removal of the endothelium completely abolished the response to acetylcholine in cirrhotic and control rings. 4. These results demonstrate that in aortic rings from cirrhotic, bile duct-ligated rats, increased production of nitric oxide, mainly of endothelial origin, is responsible for the lower contractile response to phenylephrine. Our data, however, do not support the involvement of the inducible nitric oxide synthase isoform in this alteration. In contrast, endothelial vasodilatory response to acetylcholine is not altered in this model of cirrhosis, which indicates that not all mechanisms of nitric oxide release are abnormal.     

Role of newly synthesized cholesterol or its metabolites on the regulation of bile acid biosynthesis after short-term biliary diversion in the rat

Cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in the bile acid biosynthetic pathway, is thought to be regulated by hydrophobic bile acids through negative feedback control. The role of cholesterol in the regulation of cholesterol 7 alpha-hydroxylase is more controversial, in part because of incomplete understanding of the relationship between the pathways of cholesterol synthesis and degradation. The main objective of this study was to define the interaction between these two pathways in an experimental model in which the supply of newly synthesized cholesterol was interrupted by sustained infusion of mevinolin (lovastatin), an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) or accelerated by a continuous infusion of mevalonate, a cholesterol precursor. The study was carried out in rats subjected to short-term bile fistula. In one set of experiments, rats were treated postoperatively with mevinolin (5 mg/kg loading dose followed by 2 mg/kg/hr infusion), mevalonate (180 mumol/hr infusion) or both for up to 96 hr. In a separate set of experiments, rats were infused intraduodenally with taurocholate (36 mumol/100 gm/hr for up to 96 hr). We determined cholesterol 7 alpha-hydroxylase- and HMG-CoA reductase specific activities at those time intervals, whereas bile acid synthesis rates were determined throughout the study. Compared with rats not subjected to surgery, rats with short-term biliary diversion had increases in cholesterol 7 alpha-hydroxylase activity of 259% and 827% at 48 and 96 hr, respectively. The increase in bile acid biosynthesis was less pronounced. Continuous infusion of mevinolin completely prevented increases in cholesterol 7 alpha-hydroxylase specific activity and bile acid biosynthesis at both time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ethynylestradiol on biliary excretion of bile acids, phosphatidylcolines, and cholesterol in the bile fistula rat

The effects of ethynylestradiol on endogenous bile acids, their capacity to conjugate and excrete intravenously infused cholic acid, the concentrations of biliary cholesterol and lecithin, and the individual molecular species of phosphatidylcholine have been determined in male and female Sprague-Dawley rats. Endogenous biliary bile acids were analyzed by gas-liquid chromatography-mass spectrometry. Eleven bile acids were identified and several minor bile acids, primarily muricholates, could not be completely characterized. After 5 days of treatment with ethynylestradiol (1 mg/kg per day), the percentage of cholic acid decreased and the percentage of 6beta-hydroxylated bile acids, including several monounsaturated species, increased. Ethynylestradiol caused a decrease in bile acid-independent bile flow. Intravenous infusion of cholic acid at a high concentration caused cholestasis in control animals but, after ethynylestradiol treatment, cholestasis developed during the infusion of a much lower concentration of cholate, indicating a lowered threshhold for bile acid-induced cholestasis. In the treated rats, there was a slight increase in excretion of unconjugated endogenous bile acids, and a striking impairment of conjugation of intravenously administered cholic acid. One of the few sex-related differences observed was an increased concentration of biliary phospholipids in untreated male rats. Both phospholipid and cholesterol concentrations in the bile were higher in the treated animals. The molar percentage of cholesterol was always 1-2%, but it was slightly higher in treated animals, especially males. Ethynylestradiol treatment also affected biliary phospholipid by causing a marked increase of phosphatidylcholine species containing palmitic and oleic acid residues and a decrease of species containing stearic and linoleic acid residues. There was no increase in biliary excretion of long chain polyunsaturated species, which might have indicated damage to membranes, in response to ethynylestradiol either alone or with cholic acid infusion. Some of these ethynylestradiol-induced changes in biliary bile acid and lipid excretion are probably peculiar to the rat, but others, such as the increase in molar percentage of cholesterol and cholestasis, may be relevant to disorders in man, especially cholesterol gallstones and idiopathic cholestasis of pregnancy.     

Possible mechanism by which the carbapenem antibiotic panipenem decreases the concentration of valproic acid in plasma in rats

There is evidence indicating that the carbapenem antibiotic panipenem decreases plasma concentrations of valproic acid (VPA) in epileptic patients during VPA therapy. The mechanism for panipenem-induced changes in the pharmacokinetics of VPA was investigated in rats with and without bile duct cannulation. The effect of panipenem on the pharmacokinetics of diclofenac, which undergoes extensive enterohepatic recirculation, was also examined. VPA (50 mg/kg of body weight) or diclofenac (10 mg/kg of body weight) was administered intravenously under the steady-state plasma panipenem concentration of 4 microgram/ml, which had been achieved by a constant infusion rate. Panipenem decreased the plasma VPA concentrations in rats without bile duct cannulation but did not change the volume of the initial space and protein binding of VPA. However, panipenem had no effect on the plasma VPA concentrations and the biliary excretion of VPA in rats with bile duct cannulation. The secondary increase in plasma diclofenac concentration observed in the absence of panipenem was diminished in the presence of panipenem. These findings suggest that panipenem decreases plasma VPA concentrations by suppressing its enterohepatic recirculation, probably due to a panipenem-induced decrease in the numbers of enteric bacteria.     

Physiologically based pharmacokinetic model for digoxin distribution and elimination in the rat

A plasma flow rate-limited pharmacokinetic model was developed to describe the distribution of digoxin to the heart, liver, kidneys, skeletal muscle, and GI tract in the rat. The model also provides for renal, hepatic (metabolic and biliary), and GI clearance as well as for biliary and GI secretion and GI reabsorption of digoxin. Predicted concentrations of digoxin in the heart, liver, skeletal muscle, and plasma were consistent with experimental observations in conscious rats after an intravenous dose. The model was extended to describe digoxin concentrations in the plasma of bile duct-ligated rats and ureter-ligated rats, simply by modifying appropriate clearance parameters. Excellent agreement was obtained between predicted and observed urinary excretion rates of digoxin for 12 hr after in intravenous dose to normal and bile duct-ligated rats.     

Differential diagnosis between exudate and transudate in pleural effusion

We determined the relative contributions of endogenous gastrin, histamine and cholinergic tone to basal acid secretion in chronic fistula rats. Results were compared with those for acid secretion in pylorus-ligated rats. In chronic fistula rats, YM022 ?(R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1 H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea? dose-dependently inhibited pentagastrin-stimulated acid secretion and abolished this secretion at 1 mumol/kg, s.c., but did not affect histamine- and carbachol-induced acid secretion even at 10 mumol/kg. In contrast, famotidine at 1 mumol/kg completely inhibited not only the acid secretion induced by histamine but also those by pentagastrin and carbachol. Furthermore, atropine abolished carbachol- and pentagastrin-stimulated acid secretion and significantly suppressed histamine-stimulated acid secretion at 0.1 mumol/kg. YM022 dose-dependently inhibited basal acid secretion. The YM022 dosage required to inhibit basal acid secretion is consistent with that required to suppress pentagastrin-induced acid secretion. Famotidine (1 mumol/kg) and atropine (0.1 mumol/kg) also abolished basal acid secretion. In pylorus-ligated rats, YM022 inhibited acid secretion in a dose-dependent manner; the inhibition at 1 mumol/kg, i.v. was 65%. No additional effect was observed when rats were dosed at 30 mumol/kg. Famotidine partially inhibited acid secretion in these rats, whereas atropine abolished this secretion. These results indicate that the major part of basal acid secretion in rats is attributable to endogenous gastrin via histamine- and cholinergic tone-dependent pathways. Moreover, pylorus ligation reduces the relative contribution of gastrin to acid secretion due to the activation of cholinergic tone.     

The clinical significance of type 1 fiber predominance

Having recently demonstrated that taurine supplementation prevents total parenteral nutrition (TPN)-induced cholestasis, we chose to use this model to examine plasma membrane composition in relation to bile formation. Male guinea pigs received daily a mixture of glucose and of the amino acid solution Travasol with or without added taurine (1.2 mM). After 3 days, bile was collected and liver plasma membrane fractions enriched in sinusoidal lateral membrane and bile canalicular membrane domains were isolated. In animals receiving TPN alone, bile flow and biliary secretory rate of bile acid and bicarbonate decreased significantly compared with controls. Although membrane ATPases (Na+K+ and Mg+) were unchanged, TPN induced an increase in the lipid to protein ratio and a decrease of polyunsaturated fatty acids, in conjunction with a higher content of diene conjugates in sinusoidal lateral membrane fractions. Taurine corrected these changes and, in addition, reduced significantly the cholesterol to phospholipid ratio in both membrane fractions. The data show that changes in liver cell membranes occur in TPN-induced cholestasis and suggest that free radical injury may play a role. As taurine prevented cholestasis as well as membrane changes, it is suggested that taurine should be added to amino acid solutions used for parenteral nutrition.     

VEGF-A induces expression of eNOS and iNOS in endothelial cells via VEGF receptor-2 (KDR)

Acute vanishing bile duct syndrome is a rare but established cause of progressive cholestasis in adults, is most often drug or toxin related, and is of unknown pathogenesis. It has not been reported previously in children. Stevens-Johnson syndrome is a well-recognized immune complex-mediated hypersensitivity reaction that affects all age groups, is drug or infection induced, and has classic systemic, mucosal, and dermatologic manifestations. A previously healthy child who developed acute, severe, rapidly progressive vanishing bile duct syndrome shortly after Stevens-Johnson syndrome is described; this was temporally associated with ibuprofen use. Despite therapy with ursodeoxycholic acid, prednisone, and then tacrolimus, her cholestatic disease was unrelenting, with cirrhosis shown by biopsy 6 months after presentation. This case documents acute drug-related vanishing bile duct syndrome in the pediatric age group and suggests shared immune mechanisms in the pathogenesis of both Stevens-Johnson syndrome and vanishing bile duct syndrome.     

Basal total opioid peptide release in the striatum of rats with cholestasis from bile duct resection: a study by the use of in vivo microdialysis

The opiate withdrawal-like reaction experienced by patients with cholestatic liver disease after the ingestion of the opiate antagonist nalmefene led to the hypothesis that increased opioidergic neurotransmission/neuromodulation in the central nervous system (CNS) contributes to the pathophysiology of cholestasis. The state of antinociception, which is stereospecifically reversed by naloxone, documented in rats with cholestasis from bile duct resection supports this hypothesis. To further study the opioid system in this animal model of cholestasis, we studied the release of endogenous opioid peptides into the extracellular fluid of the dorso-lateral striatum by the technique of in-vivo microdialysis. Total opioid peptide concentration in the dialysate was measured by a solid phase radioimmunoassay with an antibody directed against the N-terminus of the Tyr-Gly-Gly-Phe-X amino acid sequence after acetylation. Basal total opioid peptide release was significantly higher after surgery in both sham resected and bile duct resected animals. However, basal (unstimulated) total opioid peptide release in the striatum of rats was not altered by cholestasis. It is inferred that the opioidergic abnormalities of cholestasis are not associated with an appreciable increase in the release of endogenous opioids into the extracellular fluid of the striatum. Abnormal processing of specific opioid peptides in cholestasis however, cannot be excluded.     

Expression of the liver Na+-independent organic anion transporting polypeptide (oatp-1) in rats with bile duct ligation

BACKGROUND/AIMS: In rats with cholestasis due to bile duct ligation, the expression of the Na+-dependent taurocholate co-transporting polypeptide, the major uptake system for conjugated bile acids in hepatocytes, is down-regulated. Our purpose was to examine the expression of the organic anion transporting polypeptide, a Na+-independent uptake system for bile acids and organic anions, in rats with bile duct ligation, and to compare the expression of organic anion transporting polypeptide to that of Na+-dependent taurocholate co-transporting polypeptide. METHODS: Rats with bile duct ligation were studied after 1, 3 or 7 days. The expression of organic anion transporting polypeptide and Na+-dependent taurocholate co-transporting polypeptide proteins was examined by Western blot analysis and steady-state mRNA levels were determined by Northern blot analysis using cDNAs encoding organic anion transporting polypeptide and Na+-dependent taurocholate co-transporting polypeptide. Sham-operated animals were used as controls. RESULTS: The expression of organic anion transporting polypeptide protein was slightly, but not significantly, decreased 1 day after ligation (10.3%); it was markedly decreased after 3 days (56.9%; p<0.03) and 7 days (46.8%; p<0.05) compared to sham-operated animals. Steady-state mRNA levels of organic anion transporting polypeptide were decreased by 79.7% (p<0.04), 48.8% (p<0.02) and 57.4% (p<0.02) after 1, 3 and 7 days respectively. For comparison, Na+-dependent taurocholate co-transporting polypeptide protein and mRNA levels were decreased by 73.8% (p<0.03) and 70.0% (p<0.05) at 1 day and remained low after 3 and 7 days. CONCLUSIONS: In rats with bile duct ligation, the expression of organic anion transporting polypeptide protein and mRNA is down-regulated. Down-regulation of organic anion transporting polypeptide seems less pronounced than that of Na+-dependent taurocholate co-transporting polypeptide. Nevertheless, it could contribute to a decreased uptake of potentially toxic bile acids or organic anions in this situation.