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Original Article

Role of cyclooxygenase isoforms in encephalopathy of cirrhotic rats

Ho, Hsin-Linga,b; Hsu, Shao-Junga,b,c; Lee, Fa-Yauha,c; Huang, Hui-Chuna,c,d,*; Hsin, I-Fanga,b,c,e; Hou, Ming-Chiha,b,c; Lee, Shou-Dongc,f

Author Information
Journal of the Chinese Medical Association: November 2016 - Volume 79 - Issue 11 - p 583-588
doi: 10.1016/j.jcma.2016.05.007


    1. Introduction

    Hepatic encephalopathy (HE) is a neuropsychiatric derangement associated with acute or chronic hepatic decompensation with or without portal-systemic shunts.1,2 The disorder consists of a diversity of symptoms, varying from trivial mental instability or memory impairment to confusion, coma, and death. The initiation and maintenance of HE have been ascribed to several substances, such as ammonia, gamma-aminobutyric acid, benzodiazepines, aromatic amino acids, false neurotransmitters, endotoxin, and tumor necrosis factor-α.1–3 However, the true nature mechanism remains not totally clarified.

    Prostacyclin (PGI2), a vasodilatory prostaglandin, has been postulated to play a role in the pathogenesis of hepatic failure with encephalopathy. PGI2 participates in the mechanism of hyperdynamic circulation in portal hypertensive status. For instance, increased levels of 6-keto-prostaglandin-F (6-keto-PGF), a stable metabolite of PGI2, have been noted in animals with portal hypertension and patients with liver cirrhosis.4,5 The vasodilatory nature of PGI2 may contribute to HE6: cerebral vasculature dilatation increases capillary surface and subsequently facilitates the diffusion of noxious gut-derived compounds, such as ammonia.7 It has also been shown that PGI2 alters the permeability of the blood–brain barrier.8 Therefore, it is reasonable that PGI2 may participate, at least partly, in the pathophysiology of HE.

    The role of PGI2 during hepatic injury seems to be quite controversial. Although raised blood prostaglandin levels have been noted in massive hepatic necrosis,9 prostaglandins have been shown to ameliorate hepatic insult in terms of prolonged survival and histological improvements.10 Our previous study showed a detrimental effect of indomethacin administration on HE in rats with thioacetamide (TAA)-induced fulminant hepatic failure, which is believed to be derived from nonselective prostaglandin synthesis inhibition.11 Because indomethacin exerts a universal blockade of two prostaglandin synthesis isoenzymes, cyclooxygenase-1 (COX1) and cyclooxygenase-2 (COX2), the roles of COX isoforms in HE, indeed, require further clarification.

    As chronic liver parenchymal disease is a more prevalent form of hepatic failure and encephalopathy in clinical practice, we used bile duct-ligated cirrhotic rats to quantitatively survey the degree of HE with motor activities.12–14 The plasma levels of 6-keto-PGF and liver biochemistry parameters were also measured, and the hepatic COX isoform expressions were evaluated. Furthermore, the correlations between them were assessed.

    2. Methods

    2.1. Animal model

    Male Sprague–Dawley rats weighing 240–270 g were used for this study. The rats were caged at 24°C, with a 12-hour light–dark cycle and free access to food and water until the time of the experiments. Rats with secondary biliary cirrhosis were induced by common bile duct ligation (BDL).15 Under ketamine anesthesia (100 mg/kg, intramuscularly), the common bile duct was exposed through a midline abdominal incision, catheterized by a PE-10 catheter and doubly ligated with 3–0 silk. The first ligature was made below the junction of the hepatic ducts and the second above the entrance of the pancreatic duct. Ten percent formalin (˜10 μL/100 g) was slowly injected into the biliary tree to prevent the subsequent dilatation of the ligated residual bile duct. Thus, this animal model is abbreviated as FBDL. The PE-10 catheter was then removed and the ligatures were tightened, followed by sectioning of the common bile duct between the ligatures. The incision was then closed, and the animal was allowed to recover. A high yield of secondary biliary cirrhosis was noted at least 4 weeks after the ligation.15–17 To avoid coagulation defects, FBDL rats received weekly vitamin K injection (50 μg/kg, intramuscularly).18 The studies were performed in overnight-fasted rats, 6 weeks after the operation. Two series of studies were performed. In the first series, after measurements of the motor activities, heparinized blood samples were obtained from the inferior vena cava for alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALK-P), total bilirubin, and PGF measurements (n = 10 for each group). In the second series, livers were dissected and removed for RNA extraction and reverse transcription-polymerase chain reaction (RT-PCR; n = 9 for each group). The animal experiments were conducted according to Guide for the Care and Use of Laboratory Animals, prepared by the National Academy of Sciences and published by the National Institutes of Health (NIH publication 86-23 revised 1985).

    2.2. Measurement of motor activities

    The severity of HE was quantified with motor activities. Motor activities in an open field were determined using the Opto-Varimex animal activity meter (Columbus Instruments, Inc., Columbus, OH, USA).12,18 The Opto-Varimex activity sensors utilize high-intensity, modulated infrared light beams to detect animal motion. Animals were housed in transparent cages (17 × 17 × 8 inches), through which 30 infrared beams passed in the horizontal plane, 15 on each axis. This device differentiated nonambulatory movements (scratching, gnawing) from ambulation on the basis of consecutive interruption of the infrared monitoring beams. An additional row of infrared beams in the horizontal plane (15 on each axis) about 10 cm above the floor was used to count vertical movements. During the activity measurements, animals had no access to food or chow. All studies were performed under strictly standardized conditions in a dark room for 30 minutes. Counted numbers of total movements, ambulatory movements, and vertical movements were separately recorded to reflect the motor activities of the rats.

    2.3. Determination of plasma 6-keto-PGF levels

    Heparinized blood was centrifuged at 1789g for 10 minutes, then the plasma was separated, added with indomethacin (10 μg/ml), and stored under −80°C. At the time of measurement, samples were thawed, and 6-keto-PGF was determined with a commercially available enzyme immunoassay according to the protocol supplied by the manufacturer (R&D Systems, Minneapolis, MN, USA).

    2.4. RNA extraction and RT-PCR

    Total RNA was extracted from the vessel with an RNeasy Mini Kit according to the manufacturer's instructions (Qiagen GmbH, Hilden, Germany).19,20 A one-step RT-PCR kit (Qiagen) was used with the following components: 10 μL RT-PCR buffer containing Tris–HCl, KCl, (NH4)2SO4, and 2.5mM MgCl2; 2 μL deoxynucleotide mixture containing 400μM dATP, dCTP, dGTP, and dTTP, respectively; 2 μL enzyme mixture containing Omniscript reverse transcriptase, Sensiscript reverse transcriptase, and HotStar Taq DNA polymerase; 1 μL RNase inhibitor (40 U); 3 μL of each random primer (10 pmol/μL), and 1 μg substrate RNA. RNase-free water was added in each reaction to the final volume of 50 μL. The sequences of primers for COX1 were 5′-TGCATGTGGCTGTGGATGTCATCAA-3′ (sense) and 5′-CACTAAGACAGACCCGTCATCTCCA-3′ (antisense), respectively. Those for COX2 were 5′-ACACTCTATCACTGGCATCC- 3′ (sense) and 5′-GAAGGGACACCCTTTCACAT-3′ (antisense), respectively. A constitutively expressed gene, β-actin, was analyzed as internal control, and the primers for β-actin were 5′-TTGTAACCAACTGGGACGATATGG-3′ (sense) and 5′-GATCTTGATCTTCATGGTGCTAGG-3′ (antisense), respectively. The primers for COX1, COX2, and β-actin were designed to allow amplification of 450, 584, and 764 base-pair (bp) fragments, respectively.20,21 A negative control was included in each set of experiments. The tubes were placed in a thermocycler (Biometra T Gradient thermocycler; Biometra GmbH, Göttingen, Germany) at 50°C for 30 minutes for RT, 95°C for 15 minutes for initial denaturation, followed by 35 cycles of the following sequential steps: 30 seconds at 94°C (denaturation), 45 seconds at 56°C for COX-1, 57.2°C for COX-2, 59.6°C for β-actin (annealing), respectively, and 45 seconds at 72°C (extension). The final extension was performed at 72°C for 10 minutes. Then, 10 μL of the PCR-amplified mixture was subjected to electrophoresis on a 2% agarose gel, and DNA was visualized by ethidium bromide staining. Location of the predicted PCR products (base pairs) was confirmed with a 100-bp ladder (Gibco BRL, Gaithersburg, MD, USA) as standard size marker. The gel was then photographed, and the PCR products were quantitated by a digitalized software (Kodak Digital Science ID Image Analysis Software; Eastman Kodak Company, Rochester, NY, USA). The intensities of COX1 and COX2 signals were standardized against that of β-actin from the same RNA sample and expressed as COX1/β-actin and COX2/β-actin ratio for comparison.

    2.5. Data analysis

    All results are expressed as mean ± standard error of the mean. Statistical analyses were performed using Student t test. Results were considered statistically significant at p < 0.05.

    3. Results

    3.1. Motor activities

    Fig. 1 shows the motor activities of the FBDL and control (sham) groups. The FBDL group showed lower motor activity counts than those of the control group in total (FBDL vs. control: 1472 ± 156 vs. 2174 ± 262 counts/30 min; p = 0.034), ambulatory (824 ± 99 vs. 1443 ± 206 counts/30 min, p = 0.014), and vertical movements (431 ± 69 vs. 849 ± 145 counts/30 min, p = 0.018).

    Fig. 1
    Fig. 1:
    Individual and mean values of total, ambulatory and vertical movements (counts/30 min) of control (sham) and FBDL rats. FDBL = formalin-injected rats with bile duct ligation.

    3.2. Plasma ALT, AST, ALK-P, bilirubin, and 6-keto-PGF levels

    Table 1 shows the plasma concentrations of ALT, AST, ALK-P, bilirubin, and 6-keto-PGF of the two experimental groups. They were significantly higher in the FBDL group (all p < 0.05).

    Table 1
    Table 1:
    Parameters of hepatic injury and PGF1-α in FBDL and control groups.

    3.3. Cyclooxygenases expression

    Fig. 2 shows the hepatic COX1 and COX2 mRNA expressions. Hepatic COX2 expression was significantly higher in the FBDL group (COX2/β-actin: 0.41 ± 0.04 vs. 0.13 ± 0.03, p < 0.001). However, the hepatic COX1 mRNA expression (COX1/β-actin: 1.13 ± 0.11 vs. 0.90 ± 0.08, p = 0.117) was not significantly different between the two groups.

    Fig. 2
    Fig. 2:
    Representative diagram of agarose gel electrophoresis of COX1 and COX2 cDNA: (A) liver of control rats (A) and (B) FBDL rats (marker: 100-bp DNA ladder; COX1: 450 bp; COX2: 584 bp). Semiquantitative RT-PCR analysis: (C) COX1 expression. (D) COX2 expression. bp = base pairs. COX1 = cyclooxygenase-1; COX-2 = cyclooxygenase-2; FDBL = formalin-injected rats with bile duct ligation; RT-PCR = reverse transcription-polymerase chain reaction.

    3.4. Correlations between severity of hepatic injury, HE, and hepatic COX expression

    Figs. 3 and 4 depict the correlations among the aforementioned parameters. Plasma ALK-P and bilirubin levels were negatively correlated with total movements (p = 0.035, γ = −0.474; p = 0.009, γ = −0.569, respectively). In addition, hepatic COX2 mRNA expression was positively correlated with AST, ALK-P, bilirubin, and 6-keto-PGF (p = 0.004, γ = 0.608; p < 0.001, γ = 0.745; p = 0.001, γ = 0.700; and p < 0.001, γ = 0.722, respectively). However, there was no significant relationship between hepatic COX2 mRNA expression or 6-keto-PGF level and total movements.

    Fig. 3
    Fig. 3:
    Correlations between severity of hepatic encephalopathy (total movements) and plasma levels of alkaline phosphatase (ALK-P) and bilirubin.
    Fig. 4
    Fig. 4:
    Correlations between hepatic COX2 mRNA expression and plasma levels of AST, ALK-P, bilirubin, and 6-keto-PGF. ALK-P = alkaline phosphatase; AST = aspartate transaminase; COX-2 = cyclooxygenase-2; 6-keto-PGF = 6-keto-prostaglandin-F.

    4. Discussion

    Different from animal models with acute hepatic damage, the BDL model is an applicable model of chronic liver disease with moderate to severe degree of hepatic injury and modest or moderate degree of shunting.17,22,23 In our previous study, we demonstrated that BDL rats steadily developed HE.24 Compatible with that previous finding, we also found markedly decreased motor activities in the current FBDL group.

    In the present study, the FBDL rats showed significantly elevated plasma levels of ALT, AST, ALK-P, and bilirubin, compatible with cholestatic liver injury. The 6-keto-PGF level was also elevated, consistent with previous studies: The vasodilatory prostanoids, especially PGI2, have been implicated as mediators of the systemic and splanchnic hyperemia characteristic of portal hypertension.5,25 The increased portal venous PGI2 levels may maintain the portal hypertensive state in cirrhotic patients.26 In addition, plasma and urinary levels of 6-keto-PGF were higher in rats with portal vein stenosis and cirrhosis.27 The urinary excretion of 2,3-dinor-6-keto-PGF in cirrhotic patients was also increased.4

    PGI2 has been postulated to take part in the pathogenesis of HE.6 PGI2 altered the permeability of the blood–brain barrier.8 In addition, cerebral vasculature dilatation may increase capillary surface and subsequently facilitate the diffusion of noxious gut-derived compounds, such as ammonia.7 The absence of cerebral blood flow autoregulation in TAA-induced acute liver failure appears to arise from cerebral arteriolar dilatation28–30 and brain edema has been found in cirrhotic patients with HE.31 In addition, indomethacin, an inhibitor of cyclooxygenase, has been considered a cerebral vasoconstrictor.32 The administration of indomethacin decreased cerebral blood flow, brain water, and intracranial pressure in rats that underwent portocaval anastomosis.33 A retrospective study also revealed a strong relationship among cerebral blood flow, brain swelling, outcome, and depth of coma.34 Therefore, it is reasonable that PGI2 may participate in the pathophysiology of hepatic coma, and pharmacological manipulation of the cerebral circulation might prevent the development of brain edema in hepatic failure. However, according to our recent study,11 indomethacin, a nonselective COX inhibitor, exerted detrimental effects in terms of mortality and severity of encephalopathy in rats with TAA-induced acute liver failure. By contrast, no detrimental or therapeutic effect was identified in BDL rats receiving indomethacin.35 These findings suggest different roles of COX in acute and chronic liver failure-induced HE.

    Interestingly, a previous study identified that a COX1 inhibitor, SC-560, significantly improved HE in rats with TAA-induced fulminant hepatic failure,36 implying that COX1 plays a significant role in HE related to acute liver failure. In the current study, although hepatic COX2 expression was upregulated in FBDL rats with HE, there was no significant correlation between hepatic COX2 expression and motor activities. Rather, the motor activities correlated with ALK-P and bilirubin, two parameters of cholestatic liver damage. Furthermore, hepatic COX1 expression was not significantly different between FBDL and sham rats. The results indicated that first, compatible with our previous finding,37 HE in FBDL-cirrhotic rats is correlated with the severity of cholestatic liver injury rather than portosystemic shunting; second, the pathophysiological mechanism of HE in cirrhosis is multifactorial and not limited to prostaglandins.

    Prostaglandins have been shown to reverse acute experimental hepatic damage.10 Indomethacin administration following liver damage induced by carbon tetrachloride also increased liver cell death in rats.38 The previous investigations have indicated that PGI2 may exert a protective effect on liver damage attributed to its lysosomal membrane stabilization effect.39,40 Another study addressed that although PGI2 did not induce vasodilatory effects on the hepatic circulation, it exerted a beneficial action by inducing redistribution of flow to certain areas of the liver or by decreasing hepatic shunt flow.40 We found in the present study that hepatic COX2 mRNA expression was enhanced in BDL rats. Interestingly, the hepatic COX2 expression correlated with AST, ALK-P, and bilirubin levels. Whether it is activated following liver injury to modulate the hepatic circulation or the COX2 overexpression actually damages liver function remains to be clarified, and further studies are required.

    In conclusion, although hepatic COX2 mRNA overexpression and an increased plasma level of PGF were found in FBDL rats with HE, they were not significantly correlated with the severity of HE, suggesting a multifactorial and complicated nature of HE in cirrhosis.


    1. Sherlock S. Fulminant hepatic failure. Adv Intern Med. 1993;38:245-267.
    2. Gammal SH, Jones EA. Hepatic encephalopathy. Med Clin North Am. 1989;73:793-813.
    3. Mousseau DD, Butterworth RF. Current theories on the pathogenesis of hepatic encephalopathy. Proc Soc Exp Biol Med. 1994;206:329-344.
    4. Guarner C, Soriano G, Such J, Teixidó M, Ramis I, Bulbena O, et al. Systemic prostacyclin in cirrhotic patients. Relationship with portal hypertension and changes after intestinal decontamination. Gastroenterology. 1992;102:303-309.
    5. Sitzmann JV, Campbell KA, Wu Y, Cameron JL. Effect of portosystemic shunting on PG12 and glucagon levels in humans. Ann Surg. 1993;217:248-252.
    6. Groszmann RJ. Hyperdynamic circulation of liver disease 40 years later: pathophysiology and clinical consequences. Hepatology. 1994;20:1359-1363.
    7. Lockwood AH, Yap EWH, Wong W. Cerebral ammonia metabolism in patients with severe liver disease and minimal hepatic encephalopathy. J Cereb Blood Flow Metab. 1991;11:337-341.
    8. Awad I, Little JR, Lucas F, Skrinska V, Slugg R, Lesser RP. Treatment of acute focal cerebral ischemia with prostacyclin. Stroke. 1983;14:203-209.
    9. Rueff B, Benhamou JP. Acute hepatic necrosis and fulminant hepatic failure. Gut. 1973;14:805-815.
    10. Alp MH, Hickman R. The effect of prostaglandins, branched-chain amino acids and other drugs on the outcome of experimental acute porcine hepatic failure. J Hepatol. 1987;4:99-107.
    11. Chu CJ, Hsiao CC, Wang TF, Chan CY, Lee FY, Chang FY, et al. Prostacyclin inhibition by indomethacin aggravates hepatic damage and encephalopathy in rats with thioacetamide-induced fulminant hepatic failure. World J Gastroenterol. 2005;11:232-236.
    12. Ribeiro J, Nordlinger B, Ballet F, Cynober L, Coudray-Lucas C, Baudrimont M, et al. Intrasplenic hepatocellular transplantation corrects hepatic encephalopathy in portacaval- shunted rats. Hepatology. 1992;15:12-18.
    13. Conjeevaram HS, Nagle A, Katz A, Kaminsky-Russ K, McCullough AJ, Mullen KD. Reversal of behavior changes in rats subjected to portacaval shunt with oral neomycin therapy. Hepatology. 1994;19:1245-1250.
    14. Gammal S, Basile AS, Geller D, Skolnick P, Jones EA. Reversal of the behavioral and electrophysiologial abnormalities of an animal model of hepatic encephalopathy benzodiazepine receptor ligands. Hepatology. 1990;11:371-378.
    15. Franco F, Gigou M, Szekely AM, Bismuth H. Portal hypertension after bile duct obstruction: effect of bile diversion on portal pressure in the rat. Arch Surg. 1979;114:1064-1067.
    16. Cameron GR, Muzaffar Hasan S. Disturbances of structure and function in the liver as the result of biliary obstruction. J Pathol Bacteriol. 1958;75:333-349.
    17. Kountouras J, Billing BH, Scheuer PJ. Prolonged bile duct ligation obstruction: a new experimental model for cirrhosis in the rat. Br J Exp Pathol. 1984;65:305-311.
    18. Bengtsson F, Gage FH, Jeppsson B, Nobin A, Rosengren E. Brain monoamine metabolism and behavior in portacaval shunted rats. Exp Neurol. 1985;90:21-35.
    19. Chirgwin JM, Pryzbyla RJ, McDonald RJ, Rutter WJ. Isolation of biologically active ribonucleic acid from sources enriched in ribonuclease. Biochemistry. 1979;18:5294-5299.
    20. Chamberlain LH, Buroyne RD. Identification of a novel cysteine string protein variant and expression of cysteine string proteins in non-neuronal cells. J Biol Chem. 1996;271:7320-7323.
    21. Yang T, Singh I, Pham H, Sun D, Smart A, Schnermann JB, et al. Regulation of cyclooxygenase expression in the kidney by dietary salt intake. Am J Physiol. 1998;274:F481-F489.
    22. Lebrec D, Blanchet L. Effect of two models of portal hypertension on splanchnic organ blood flow in the rat. Clin Sci (Lond). 1985;68:23-28.
    23. Koyama K, Muto I, Yamauchi H, akagi Y, Anezaki T. Biochemical study of fibrosis in the rat liver in biliary obstruction. Tohoku J Exp Med. 1975;116:161-172.
    24. Chan CY, Huang SW, Wang TF, Lu RH, Lee FY, Chang FY, et al. Lack of detrimental effects of nitric oxide inhibition in bile duct-ligated rats with hepatic encephalopathy. Eur J Clin Invest. 2004;34:122-128.
    25. Fernandez M, Garcia-Pagan JC, Casadevall M, Mourelle MI, Pique JM, Bosch J, et al. Acute and chronic cyclooxygenase blockage in portal-hypertensive rats: influence in nitric oxide biosynthesis. Gastroenterology. 1996;110:1529-1535.
    26. Yin J, Leng X, Zhu J. Plasma prostacyclin (PGI2) levels in peripheral venous, arterial and portal venous blood in cirrhotic patients with portal hypertension and their clinical implication. Zhonghua Wai Ke Za Zhi. 1995;33:563-565.
    27. Oberti F, Sogni P, Cailmail S, Moreau R, Pipy B, Lebrec D. Role of prostacyclin in hemodynamic alterations in conscious rats with extrahepatic or intrahepatic portal hypertension. Hepatology. 1993;18:621-627.
    28. Larsen FS, Knudsen GM, Paulson OB, Vilstrup H. Cerebral blood flow autoregulation is absent in rats with fulminant hepatic failure. J Hepatol. 1994;21:491-495.
    29. Larsen FS, Ejlersen E, Hansen BA, Knudsen GM, Tygstrup N, Secher NH. Functional loss of cerebral blood flow autoregulation in patients with fulminant hepatic failure. J Hepatol. 1995;23:212-217.
    30. Stanley NN, Salisbury BG, McHenry LCJ, Cherniack NS. Effect of liver failure in the response of ventilation and cerebral circulation to carbon dioxide in man and in the goat. Clin Sci Mol Med. 1975;49:157-169.
    31. Donovan JP, Shafer DF, Shaw BW Jr, Sorrell MF. Cerebral oedema and increased intracranial pressure in chronic liver disease. Lancet. 1998;351:719-721.
    32. Harrigan MR, Tuteja S, Neudeck BL. Indomethacin in the management of elevated intracranial pressure: a review. J Neurotrauma. 1997;14:637-650.
    33. Chung C, Gottstein J, Blei AT. Indomethacin prevents the development of experimental ammonia-induced brain edema in rats after portocaval anastomosis. Hepatology. 2001;34:249-254.
    34. Aggarwal S, Kramer D, Yonas H, Obrist W, Kang Y, Martin M, et al. Cerebral hemodynamic and changes in fulminant hepatic failure: a retrospective study. Hepatology. 1994;19:80-87.
    35. Chan CY, Lee FY, Wang TF, Huang SW, Chang FY, Lu RH, et al. Lack of detrimental or therapeutic effects of cyclooxygenase inhibition in bile duct-ligated rats with hepatic encephalopathy. J Gastroenterol Hepatol. 2006;21:1483-1487.
    36. Chang CC, Wang SS, Huang HC, Chan CY, Lee FY, Lin HC, et al. Selective cyclooxygenase inhibition improves hepatic encephalopathy in fulminant hepatic failure of rat. Eur J Pharmacol. 2011;666:226-232.
    37. Hsin IF, Wang SS, Huang HC, Lee FY, Chan CY, Chang CC, et al. Portosystemic collaterals are not prerequisites for the development of hepatic encephalopathy in cirrhotic rats. J Chin Med Assoc. 2012;75:3-9.
    38. Guarner F, Fremont-Smith M, Prieto J. Cytoprotective effect of prostaglandins on isolated rat liver cells. Liver. 1985;5:35-39.
    39. Lefer AM, Ogletree ML, Smith JB, Silver MJ, Nicolaou KC, Barnette WE, et al. Prostacyclin: a potentially valuable agent for preserving myocardial tissue in acute myocardial ischemia. Science. 1978;200:52-54.
    40. Araki H, Lefer AM. Cytoprotective actions of prostacyclin during hypoxia in the isolated perfused cat liver. Am J Physiol. 1980;238:H176-H181.

    bile duct ligation; cyclooxygenase; hepatic encephalopathy; liver cirrhosis; prostacyclin

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