In vivo gene transfer of endothelial nitric oxide synthase decreases portal pressure in anaesthetised carbon tetrachloride cirrhotic rats

BACKGROUND: Portal hypertension in cirrhosis results from enhanced intrahepatic resistance to an augmented inflow. The former is partly due to an imbalance between intrahepatic vasoconstriction and vasodilatation. Enhanced endothelin-1 and decreased activity of hepatic constitutive endothelial nitric oxide synthase (NOS 3) was reported in carbon tetrachloride (CCl(4)) cirrhotic rat liver. AIMS: To study whether an increase in hepatic NOS 3 could be obtained in the CCl(4) cirrhotic rat liver by in vivo cDNA transfer and to investigate a possible effect on portal pressure. METHODS: Hepatic NOS 3 immunohistochemistry and western blotting were used to measure the amount of NOS 3 protein. Recombinant adenovirus, carrying cDNA encoding human NOS 3, was injected into the portal vein of CCl(4) cirrhotic rats. Cirrhotic controls received carrier buffer, naked adenovirus, or adenovirus carrying the lac Z gene. RESULTS: NOS 3 immunoreactivity and amount of protein (western blotting) were significantly decreased in CCl(4) cirrhotic livers. Following cDNA transfer, NOS 3 expression and the amount of protein were partially restored. Portal pressure was 11.4 (1.6) mm Hg in untreated cirrhotic (n=9) and 11.8 (0.6) in lac Z transfected (n=4) cirrhotic rats but was reduced to 7.8 (1.0) mm Hg (n=9) five days after NOS 3 cDNA transfer. No changes were observed in systemic haemodynamics, in liver tests or urinary nitrates, or in NOS 3 expression in lung or kidney, indicating a highly selective transfer. CONCLUSIONS: NOS 3 cDNA transfer to cirrhotic rat liver is feasible and the increase in hepatic NOS 3 leads to a marked decrease in portal hypertension without systemic effects. These data indicate a major haemodynamic role of intrahepatic NOS 3 in the pathogenesis of portal hypertension in CCl(4) cirrhosis.     

The effect of augmenting portal venous inflow on intrahepatic pressure and resistance in the isolated perfused porcine liver

BACKGROUND/AIMS: The literature regarding the relationship between portal venous flow and pressure is controversial. The aim of this study was to examine the effects of doubling portal venous inflow on hepatic hemodynamics. METHODOLOGY: Portal venous pressure, intrahepatic portal venous resistance, hepatic arterial pressure and intrahepatic arterial resistance were assessed during basal portal venous inflow (756 +/- 142 mL/min; mean +/- SD) and enhanced portal venous inflow (1512 +/- 284 mL/min) in an isolated perfused normal porcine liver model (n = 6). Hepatic arterial flow was maintained constant throughout the experiments. RESULTS: During the period of enhanced portal venous flow there was an increase in: portal venous pressure (from 9 +/- 2 to 22 +/- 7 mm Hg, P = 0.0076); the difference between portal venous and hepatic venous pressures (from 2 +/- 2 to 10 +/- 5 mm Hg; P = 0.0289); hepatic arterial pressure (from 84 +/- 9 to 151 +/- 33 mm Hg, P = 0.0019); and intrahepatic arterial resistance (from 0.3488 +/- 0.0637 to 0.6387 +/- 0.2020, P = 0.0046). CONCLUSIONS: The increases in hepatic artery pressure and intrahepatic arterial resistance are a result of the hepatic arterial 'buffer response', a phenomenon not previously demonstrated in vitro. The magnitude of the observed changes in portal venous and hepatic venous pressure leads to the conclusion that, in the porcine liver, the intrahepatic venous resistance sites react by constricting to increases in portal venous inflow.     

Increased blood flow through the portal system in cirrhotic rats

Portal venous pressure is the result of the interplay between portal venous blood flow and the vascular resistance offered to that flow. Whether portal hypertension is maintained only by an increased portal venous resistance or also by an increased blood flow within the portal venous system is still open to speculation. To resolve these differences, splanchnic and systemic hemodynamics were evaluated in cirrhotic rats, induced by CCl4. Blood flow and portal-systemic shunting were measured by radioactive microsphere techniques. All cirrhotic rats had portal hypertension (portal venous pressure 13.5 +/- 1.1 vs. 9.0 +/- 0.5 mmHg, in normal control rats; p less than 0.01), but portal-systemic shunting in cirrhosis (31% +/- 13% vs. 0.2% +/- 0.02%; p less than 0.05) was variable, ranging from 1% to 97%. Portal venous inflow, the total blood flow within the portal system, was increased in cirrhotic rats (5.75 +/- 0.04 vs. 4.52 +/- 0.36 ml/min per 100 g; p less than 0.05). Total splanchnic arterial resistance was reduced in cirrhotic rats (3.3 +/- 0.2 vs. 5.8 +/- 0.5 dyn X s X cm-5 X 10(5); p less than 0.01). Portal venous resistance, however, was not abnormally elevated in cirrhotic rats (4.6 +/- 0.5 vs. 4.7 +/- 0.5 dyn X s X cm-5 X 10(4), p = NS). Splanchnic hemodynamics in cirrhotic rats demonstrate that portal hypertension is maintained, at least in part, by a hyperdynamic portal venous inflow. The hemodynamic data in cirrhotic rats provided evidence that supports the role of an increased portal blood flow in portal hypertension and gives a quantitative definition of splanchnic hemodynamics in intrahepatic portal hypertension.     

Nitroflurbiprofen, a nitric oxide-releasing cyclooxygenase inhibitor, improves cirrhotic portal hypertension in rats

BACKGROUND & AIMS: We studied whether administration of nitroflurbiprofen (HCT-1026), a cyclooxygenase inhibitor with nitric oxide (NO)-donating properties, modulates the increased intrahepatic vascular tone in portal hypertensive cirrhotic rats. METHODS: In vivo hemodynamic measurements (n = 8/condition) and evaluation of the increased intrahepatic resistance by in situ perfusion (n = 5/condition) were performed in rats with thioacetamide-induced cirrhosis that received either nitroflurbiprofen (45 mg/kg), flurbiprofen (30 mg/kg, equimolar concentration to nitroflurbiprofen), or vehicle by intraperitoneal injection 24 hours and 1 hour prior to the measurements. Additionally, we evaluated the effect of acute administration of both drugs (250 micromol/L) on the intrahepatic vascular tone in the in situ perfused cirrhotic rat liver (endothelial dysfunction and hyperresponsiveness to methoxamine) and on hepatic stellate cell contraction in vitro. Typical systemic adverse effects of nonsteroidal anti-inflammatory drugs, such as gastrointestinal ulceration, renal insufficiency, and hepatotoxicity, were actively explored. RESULTS: In vivo, nitroflurbiprofen and flurbiprofen equally decreased portal pressure (8 +/- 0.8 and 8.4 +/- 0.1 mm Hg, respectively, vs 11.8 +/- 0.6 mm Hg) and reduced the total intrahepatic vascular resistance. Systemic hypotension was not aggravated in the different treatment groups (P = .291). In the perfused cirrhotic liver, both drugs improved endothelial dysfunction and hyperresponsiveness. This was associated with a decreased hepatic thromboxane A(2)-production and an increased intrahepatic nitrate/nitrite level. In vitro, nitroflurbiprofen, more than flurbiprofen, decreased hepatic stellate cells contraction. Flurbiprofen-treated rats showed severe gastrointestinal ulcerations (bleeding in 3/8 rats) and nefrotoxicity, which was not observed in nitroflurbiprofen-treated cirrhotic rats. CONCLUSIONS: Treatment with nitroflurbiprofen, an NO-releasing cyclooxygenase inhibitor, improves portal hypertension without major adverse effects in thioacetamide-induced cirrhotic rats by attenuating intrahepatic vascular resistance, endothelial dysfunction, and hepatic hyperreactivity to vasoconstrictors.     

Modulation of the hyperdynamic circulation of cirrhotic rats by nitric oxide inhibition.

The effects of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide (NO) biosynthesis on the splanchnic and systemic circulation, were investigated in rats with cirrhosis induced by carbon tetrachloride. Portal hypertension in these rats was accompanied by decreased arterial blood pressure and peripheral vascular resistance as well as by splanchnic vasodilation with increased portal venous inflow and decreased splanchnic resistance. Intravenous bolus administration of L-NMMA (25 mg/kg) significantly increased systemic blood pressure and decreased cardiac output. L-NMMA also significantly increased systemic and splanchnic vascular resistance; whereas blood flow to the stomach, small intestine, colon, pancreas, mesentery, spleen, and kidney was decreased significantly. L-NMMA did not alter the portal pressure or portosystemic shunting in these cirrhotic rats, yet portal vascular resistance increased, suggesting effects on the intrahepatic and collateral circulation. Pretreatment with L-arginine (300 mg/kg) prevented the hemodynamic changes induced by L-NMMA. These findings support the concept that local excess formation of NO contributes to changes in splanchnic circulation associated with portal hypertension in cirrhosis.     

Evidence for normal nitric oxide-mediated vasodilator tone in conscious rats with cirrhosis.

Because it has been hypothesized that the hyperkinetic circulation in portal hypertension is the result of increased synthesis of nitric oxide, we compared the hemodynamic effects of nitric oxide synthesis--specific agonist (L-arginine) and antagonist between normal and cirrhotic conscious rats. The dose-response curves showed that L-arginine significantly decreased arterial pressure and increased heart rate. These changes started at the 200 mg/kg dose and were similar in both groups of rats. In both groups of rats NG-monomethyl-L-arginine (25 mg/kg) significantly decreased cardiac output by 35%. In cirrhotic rats, NG-monomethyl-L-arginine decreased portal pressure from 15.3 +/- 0.9 mm Hg to 13.6 +/- 0.7 mm Hg and portal tributary blood flow from 7.8 +/- 0.7 ml.min-1.100 gm-1 to 5.9 +/- 0.7 ml.min-1.100 gm-1; it significantly increased portal territory vascular resistance from 950 +/- 108 dyn.sec.cm-5.100 gm-1 x 10(3) to 1,579 +/- 258 dyn.sec.cm-5.100 gm-1 x 10(3). In normal rats, portal tributary blood flow decreased similarly, by 27%, and portal territory vascular resistance increased by 55%. In neither group was hepatic arterial blood flow altered. Before and after NG-monomethyl-L-arginine administration, arterial cyclic GMP concentrations were not significantly different between normal and cirrhotic rats. In conclusion, this study shows evidence of a normal role for nitric oxide-mediated vasodilatation in rats with cirrhosis and that inhibition of nitric oxide synthesis reduces portal hypertension. These results did not support the hypothesis that nitric oxide synthesis is increased in cirrhosis.     

Treatment of Portal Hypertension with NCX‐1000, a Liver‐Specific NO donor. A Review of Its Current Status

Portal hypertension, a life threatening complication of liver cirrhosis, results from increased intrahepatic resistance and increased portal blood inflow through a hyperdynamic splanchnic system. The increased intrahepatic vascular tone is the result of an enhanced activity of endogenous vasoconstrictors and a deficiency of nitric oxide (NO) release by sinusoidal endothelial cells. These pathophysiological events provide the rational basis for using NO‐based therapies for the treatment of portal hypertension. Clinical studies have demonstrated that nitrate therapy results in a significant reduction of portal pressure as assessed by hepatic venous portal gradient but causes vasodilation in both systemic arterial and venous vascular beds, aggravating the progression of the vasodilatory syndrome of cirrhotic patients. For this reason, the ideal drug for the treatment of portal hypertension should act by decreasing intrahepatic vascular resistance, without worsening the splanchnic/systemic vasodilatation. NCX‐1000 is the prototype of a family of NO‐releasing derivatives of ursodeoxycholic acid (UDCA). These compounds are releasing selectively, from parenchymal and non‐parenchymal hepatic cells, biologically active NO into the liver microcirculation with no detectable effect on systemic circulation. Preclinical studies have shown that long‐ and short‐term administration of NCX‐1000 to rodents with chronic liver injury protects against the development of portal hypertension and reduces the intrahepatic hyperreactivity to α₁‐adrenoceptor agonists. The finding of increased liver nitrite/nitrate content in NCX‐1000‐treated animals together with an increase in cGMP levels in their liver homogenates suggests that this nitro‐compound behaves as a liver‐selective NO donor. In contrast to conventional NO‐donors such as isosorbide mono‐ and di‐nitrate, which are also used for primary and secondary prevention of gastrointestinal bleeding, NCX‐1000 has no effect on mean arterial pressure in either normal or cirrhotic animals indicating the absence of adverse systemic effect. In summary, these data suggest that NCX‐1000 may provide a novel therapy for the treatment of patients with portal hypertension.     

Endothelin-1 and heme oxygenase-1 as modulators of sinusoidal tone in the stress-exposed rat liver

Heme oxygenase (HO)-1 is up-regulated after ischemia/reperfusion and contributes to maintenance of hepatic perfusion and integrity. Blockade of HO-1 leads to an increased portal pressor response in the stress-exposed liver. We tested whether the increase in portal pressure reflects unmasking of a concomitant up-regulation of the vasoconstrictor endothelin (ET)-1. Hemorrhagic shock induced messenger RNAs encoding HO-1 (16-fold) and ET-1 (9-fold) with a similar time course in the liver. At maximum induction of both mediators, rats received either vehicle or the endothelin ET(A/B) antagonist bosentan (10 mg/kg intravenously). Subsequently, the HO pathway was blocked in all animals by tin-protoporphyrin (SnPP)-IX (50 micromol/kg intravenously). Portal and sinusoidal hemodynamics were measured using microflow probes and intravital microscopy, respectively. Blockade of the HO pathway led to a significant increase in portal resistance (sham/SnPP-IX, 0.17 +/- 0.046 mm Hg. min. mL(-1); shock/vehicle/SnPP-IX, 0.57 +/- 0.148 mm Hg. min. mL(-1); P <.05) and a decrease in sinusoids conducting flow (shock/vehicle/SnPP-IX: baseline, 28.3 +/- 0.85 sinusoids/mm; 10 minutes after SnPP-IX, 23.1 +/- 1.09 sinusoids/mm; P <.05). Intravital microscopy showed narrowing of failing sinusoids colocalizing with stellate cells after blockade of the HO pathway. Blockade of ET(A/B) receptors attenuated the increase in portal resistance (shock/bosentan/SnPP-IX, 0.29 +/- 0.051 mm Hg. min. mL(-1)) and prevented sinusoidal perfusion failure (shock/bosentan/SnPP-IX: baseline, 28.2 +/- 0.97 sinusoids/mm; 10 minutes after SnPP-IX, 28.8 +/- 1.18 sinusoids/mm) as well as sinusoidal narrowing. In conclusion, a functional interaction of the up-regulated vasodilatory HO system and the vasoconstrictor ET-1 on the sinusoidal level exists under stress conditions. Both mediator systems affect sinusoidal diameter via direct action on hepatic stellate cells in vivo.     

Acute effect of propranolol on splanchnic circulation in normal and portal hypertensive rats

Propranolol decreases portal venous pressure in patients with cirrhosis but no method is available in man to study the effect of this beta-blocker on splanchnic organ blood flow. Because in rats, the microsphere method allows evaluation of regional blood flow, the acute effect of propranolol on both splanchnic and systemic circulations was studied in normal rats and in rats with portal hypertension due to portal vein stenosis. Portal venous pressure significantly decreased during propranolol administration in normal (5.6 +/- 1.0-4.7 +/- 1.1 mm Hg; mean +/- SD) as well as in portal hypertensive rats (11.7 +/- 2.3-10.3 +/- 1.8 mm Hg). Propranolol slightly decreased cardiac output and arterial pressure in all rats. Portal tributary blood flow was significantly reduced by propranolol in normal rats (17.4 +/- 3.0-11.3 +/- 2.2 ml/min) and in portal hypertensive rats (23.7 +/- 5.0-16.6 +/- 3.3 ml/min). Accordingly vascular resistance of the different organs in the portal venous territory increased in these rats receiving propranolol. The percentage of the decrease in portal tributary blood flow was significantly more marked than the percentage of reduction in cardiac output in portal hypertensive rats but, in normal rats, these percentages were parallel. Hepatic arterial blood flow did not change or slightly increased and, consequently, hepatic arterial vascular resistance decreased. These findings further clarify the marked effects of propranolol on splanchnic circulation.     

Effect of hepatic nerves, norepinephrine, angiotensin, and elevated central venous pressure on postsinusoidal resistance sites and intrahepatic pressures in cats

Portal venous pressure was controlled by resistance localized to specific sites in hepatic lobar veins in cats. All of the pressure drop from the portal vein to the vena cava occurred across postsinusoidal vessels; portal pressure, lobar venous pressure, and, therefore, sinusoidal pressure were not significantly different. Norepinephrine and angiotensin infusions (intraportal) caused elevation in portal pressure due to constriction of hepatic venous resistance sites as well as some constriction of presinusoidal (portal or sinusoidal) resistance sites. At low doses of norepinephrine presinusoidal constriction dominated whereas at higher doses the postsinusoidal constriction increased proportionately more. Hepatic nerve stimulation produced a similar response measured at an early time (1 min), but by 3 min the presinusoidal constriction showed complete escape so that elevated portal pressure was entirely due to hepatic venous constriction. The same site that provided basal vascular resistance also provided the increased hepatic venous resistance with nerve stimulation and infusion of angiotensin and norepinephrine. Rapid elevation of central venous pressure (CVP) caused elevated sinusoidal pressure. At high CVP (16 mm Hg), 75% of a rise in CVP was transmitted whereas at normal CVP (less than 4.5 mm Hg) less than 20% transmission occurred. The presence of a high resistance in the hepatic veins protected intrahepatic pressure from the effects of normal fluctuation of CVP.     

The methionine connection: homocysteine and hydrogen sulfide exert opposite effects on hepatic microcirculation in rats

Increased intrahepatic resistance in cirrhotic livers is caused by endothelial dysfunction and impaired formation of two gaseous vasodilators, nitric oxide (NO) and hydrogen sulfide (H(2)S). Homocysteine, a sulfur-containing amino acid and H(2)S precursor, is formed from hepatic methionine metabolism. In the systemic circulation, hyperhomocystenemia impairs vasodilation and NO production from endothelial cells. Increased blood levels of homocysteine are common in patients with liver cirrhosis. In this study, we demonstrate that acute liver perfusion with homocysteine impairs NO formation and intrahepatic vascular relaxation induced by acetylcholine in methoxamine-precontracted normal livers (7.3% +/- 3.0% versus 26% +/- 2.7%; P < 0.0001). In rats with mild, diet-induced hyperhomocystenemia, the vasodilating activity of acetylcholine was markedly attenuated, and incremental increases in flow induced a greater percentage of increases in perfusion pressure than in control livers. Compared with normal rats, animals rendered cirrhotic by 12 weeks' administration of carbon tetrachloride exhibited a greater percentage of increments in perfusion pressure in response to shear stress (P < 0.05), and intrahepatic resistance to incremental increases in flow was further enhanced by homocysteine (P < 0.05). In normal hyperhomocysteinemic and cirrhotic rat livers, endothelial dysfunction caused by homocysteine was reversed by perfusion of the livers with sodium sulfide. Homocysteine reduced NO release from sinusoidal endothelial cells and also caused hepatic stellate cell contraction; this suggests a dual mechanism of action, with the latter effect being counteracted by H(2)S. CONCLUSION: Impaired vasodilation and hepatic stellate cell contraction caused by homocysteine contribute to the dynamic component of portal hypertension.     

Hemodynamic effects of terbutaline, a beta 2-adrenoceptor agonist, in conscious rats with secondary biliary cirrhosis.

The hemodynamic responses to terbutaline - a selective beta 2-adrenoceptor agonist - were studied in conscious normal rats and in conscious rats with secondary biliary cirrhosis. Compared with those of normal rats, dose-response curves in cirrhotic rats indicated significantly decreased reactivity in arterial pressure and heart rate. Half-maximal effective dose was not significantly different between the two groups. Terbutaline induced significant, dose-dependent decreases in portal pressure in both normal rats (9.3%) and cirrhotic rats (13.8%). In normal rats, terbutaline administration (32 micrograms.min-1.kg-1 body wt) increased both cardiac output and portal tributary blood flow, thus mimicking hemodynamic changes in cirrhotic rats. In cirrhotic rats, despite a significant increase in portal tributary blood flow (from 19.9 +/- 1.7 ml/min to 22.7 +/- 1.5 ml/min), terbutaline decreased portal pressure from 17.4 +/- 1.0 mm Hg to 15.0 +/- 0.8 mm Hg. This study indicates that increased beta 2-adrenoceptor stimulation in cirrhotic rats may be involved in hyperdynamic circulation. The association of a decreased portal pressure and increased splanchnic blood flow suggests that beta 2-adrenoceptor stimulation may modulate hepatic and portal collateral vascular resistance.     

Liposome-mediated gene transfer of endothelial nitric oxide synthase to cirrhotic rat liver decreases intrahepatic vascular resistance

Background and Aims:  Nitric oxide (NO) production by endothelial nitric oxide synthase (eNOS) in sinusoidal endothelial cells is reduced in the injured liver and leads to intrahepatic portal hypertension. The present study evaluates the effects of liposome-mediated gene transfer of eNOS on the intrahepatic vascular resistance and portal venous pressure (PVP) in cirrhotic rats.
Methods:  Hepatic cirrhosis was induced in male Sprague–Dawley rats by intraperitoneal injection of carbon tetrachloride (CCl₄), whereas the control normal rats were given the same dose of peanut oil. Plasmid eukaryotic expression vector (liposome-pcDNA3/eNOS) was injected into the portal vein of CCl₄ cirrhotic rats, whereas cirrhotic controls received the same dose of naked plasmid (liposome-pcDNA3) or Tris buffer, and control normal rats received the same dose of Tris buffer. Five days after gene transfer, the levels of eNOS mRNA and protein, NO production, PVP and the changes of hepatic intrahepatic vascular resistance were investigated.
Results:  Five days after eNOS gene transfer, the levels of eNOS mRNA, eNOS protein and NO production in cirrhotic rats increased remarkably, while hepatic vascular resistance and PVP decreased significantly in cirrhotic rats.
Conclusion:  Liposome-mediated eNOS gene transfer via intraportal injection is feasible and the increase of intrahepatic eNOS leads to a marked decrease in introhepatic vascular resistance and PVP. These data indicate that intrahepatic eNOS plays an important role in the pathogenesis of portal hypertension and gene transfer of eNOS is a potential and novel therapy for portal hypertension.     

The effect of mechanically enhancing portal venous inflow on hepatic oxygenation, microcirculation, and function in a rabbit model with extensive hepatic fibrosis.

Enhancing the portal venous blood flow (PVBF) has been shown to reduce portal pressure and intrahepatic vascular resistance and to improve liver function in isolated cirrhotic rodent livers in vitro. The aim of this study was to assess the short-term effect of mechanically pumping the portal inflow on hepatic microcirculation (HM), oxygenation, and function in an animal model of extensive hepatic fibrosis. New Zealand white rabbits underwent laparotomy and exposure of the liver: group 1 (n = 7) were normal controls; group 2 (n = 7) had hepatic fibrosis. Total hepatic blood flow (THBF) and HM was measured along with continuous monitoring of intrahepatic tissue oxygenation using near infrared spectroscopy (NIRS). Baseline hepatic hemodynamics and liver function were measured in both groups. PVBF was then increased by 50% over a 3-hour period in the hepatic fibrosis group using a miniature portal pump designed for human implantation, and the hemodynamics were monitored continuously. Liver function tests were repeated after portal pumping. In comparison with normal controls, animals with hepatic fibrosis had a higher portal pressure (13.0 +/- 3.6 vs. 3.7 +/- 1.4 mm Hg, P <.001, mean +/- SD vs. controls), reduced PVBF (52.4 +/- 24.6 vs. 96.9 +/- 21.1 mL/min, P =.003), and increased portal vascular resistance (P =. 001). THBF and flow in the HM was lower than in controls, and liver function tests were abnormal. After a 3-hour period of enhanced portal flow in animals with hepatic fibrosis, the portal pressure greatly reduced (13.0 +/- 3.6 to 2.5 +/- 1.1 mm Hg, P <.001) as did the intrahepatic portal resistance (0.32 +/- 0.18 to 0.04 +/- 0.03 mm Hg/mL/min, P =.006). Flow in the HM improved (143 +/- 16 to 173 +/- 14 flux units, P =.006) and was associated with improved hepatic tissue oxygenation, tissue oxy-hemoglobin (HbO2) and cytochrome oxidase being increased by 24.4 +/- 7.5 and 5.65 +/- 2.30 micromol/L above the baseline value (P <.001), respectively. A 3-hour period of mechanical portal pumping produced a dramatic improvement in liver function, bilirubin (41.1 +/- 25.9 to 10.0 +/- 5.9 micromol/L, P =. 040), aspartate transaminase (AST) (135.5 +/- 52.3 to 56.3 +/- 19.8 U/L, P =.006) and lactate dehydrogenase (LDH) (2,030.1 +/- 796.3 to 1,309.8 +/- 431.6 IU/L, P =.006; prepumping vs. postpumping, all P <. 050). In conclusion, portal pumping in this rabbit model with extensive hepatic fibrosis improved liver parenchymal perfusion, oxygenation, and function.     

Measurement of Intrahepatic Pressure as an Index of Hepatic Sinusoidal Pressure

Intrahepatic pressure was measured in 148 patients with liver disease (32 outpatients, 116 inpatients) and 13 controls with almost normal liver histology (inpatients), with a 23-gauge needle (inner diameter 0.38 mm). Intrahepatic pressure was significantly elevated in the group order of chronic active hepatitis without bridging necrosis (n = 17, 9.2 +/- 3.0 mm Hg), chronic active hepatitis with bridging necrosis (n = 24, 12.3 +/- 5.7), and posthepatitic liver cirrhosis (n = 65, 18.8 +/- 4.2), compared with controls (n = 13, 6.8 +/- 2.7), whereas it was not elevated in the group of idiopathic portal hypertension (n = 9, 7.8 +/- 2.5 mm Hg), acute hepatitis (n = 10, 8.4 +/- 2.6 mm Hg), and chronic persistent hepatitis (n = 23, 7.9 +/- 2.7 mm Hg), compared with controls. As complications, four patients had abdominal discomfort continuing for more than a day; however, patients were allowed to walk after they had rested on their beds for 30 min. In 37 patients (27 with cirrhosis, seven idiopathic portal hypertension, and three others), portal vein and/or hepatic vein catheterization was performed during the same procedure of intrahepatic pressure measurement. Intrahepatic pressure showed significant correlations with corrected wedged hepatic vein pressure (r = 0.91), portohepatic gradient (r = 0.69), wedged hepatic vein pressure (r = 0.79), and portal vein pressure (r = 0.68). Slopes were 0.97, 0.83, 0.66, and 0.65, respectively. In conclusion, intrahepatic pressure reflects hepatic sinusoidal pressure (corrected wedged hepatic vein pressure), and intrahepatic pressure starts to elevate at the stage of chronic active hepatitis.     

Significance of hepatic arterial responsiveness for adequate tissue oxygenation upon portal vein occlusion in cirrhotic livers

We investigated sinusoidal blood flow and hepatic tissue oxygenation during portal vein occlusion in cirrhotic rat livers to examine the effect of cirrhosis on the properties of hepatic microvascular blood flow regulation. After 8 weeks of CCl4/phenobarbital sodium treatment to induce cirrhosis Sprague-Dawley rats were prepared surgically to allow assessment of portal venous and hepatic arterial inflow using miniaturized flow probes with simultaneous analysis of hepatic microcirculation and tissue oxygenation by fluorescence microscopy and polarographic oxymetry. Age-matched noncirrhotic animals served as controls. Upon portal vein occlusion in cirrhotic livers (flow reduction to < 20%), hepatic arterial blood flow increased 1.5-fold (61 +/- 8 ml/min per 100 g liver) of baseline (40 +/- 7 ml/min per 100 g liver), reflecting an appropriate hepatic arterial buffer response (HABR), similarly as seen in control livers. The net result was a reduction in total liver inflow from 90 +/- 12 to 72 +/- 11 ml/min per 100 g liver, which was associated with a significant decrease in both sinusoidal red blood cell velocity and volumetric blood flow to approx. 71% and 76% of baseline values. However, portal vein occlusion did not cause a deterioration in hepatic tissue pO2 (11 +/- 3 vs. 10 +/- 3 mmHg at baseline). Sinusoidal diameters were found unchanged, disproving a major role of the sinusoidal tone in the regulation of HABR. Microvascular response of cirrhotic livers did not generally differ from that in noncirrhotic livers upon portal inflow restriction. We conclude that HABR in cirrhotic livers operates sufficiently to meet the liver tissue oxygen demand, most probably by an increased relative contribution of arterial perfusion of hepatic sinusoids.     

Postprandial splanchnic haemodynamic changes in patients with liver cirrhosis and patent paraumbilical vein

OBJECTIVE: The haemodynamic changes induced by a meal on collateral vessels in portal hypertensive cirrhotic patients are not well characterized. We aimed to study the postprandial modifications of splanchnic circulation in patients with a patent paraumbilical vein (PUV). METHODS: We studied 10 cirrhotic patients with patent PUV and 10 matched cirrhotic patients without PUV, by using echo colour Doppler at baseline and 15, 30 and 45 min after a standard mixed liquid meal (400 ml; 600 kcal). Calibre and blood flow velocities of the superior mesenteric artery, portal vein and PUV were obtained; congestion index of portal vein, portal blood flow, paraumbilical blood flow and effective portal liver perfusion were calculated; intrahepatic and intrasplenic arterial resistance and pulsatility indexes were recorded. RESULTS: We observed a postprandial splanchnic hyperaemia (superior mesenteric artery and portal vein blood flow increased after the meal in both groups; ANOVA P < 0.05), with no changes of hepatic impedance. In PUV patients, PUV constricted significantly postprandially, maximally at 30 min (calibre -17.5 +/- 7.0%; P = 0.003). Intrasplenic impedance, which may reflect portal pressure, increased, maximally at 30 min (pulsatility index +22.6 +/- 27.0%; P = 0.01), and inversely correlated with PUV vasoconstriction (R = 0.75, P = 0.01). In non-PUV patients intrasplenic impedance did not change. Portal liver perfusion increased similarly in both groups. CONCLUSIONS: PUV constricts after the meal, and this vasoconstriction is associated with an increase of splenic impedance which may indicate the postprandial increase of portal pressure observed in cirrhosis. The increase in postprandial portal liver perfusion in the PUV group is allowed by a paradox constriction of the collateral vessel.     

Chronic portal venous hypertension. The effect on liver blood flow and liver function and the development of esophageal varices

Portal venous hypertension was induced in G?ttingen minipigs by banding the portal vein. The pigs were checked repeatedly during the following 24 weeks. Portal pressure increased immediately on banding, from 8.4 +/- 0.7 mm Hg to 19.4 +/- 0.7 mm Hg, and remained constant throughout the observation period. Within 5 weeks all pigs developed esophageal varices, as demonstrated by portal angiography and endoscopy. The experimentally induced portal hypertension was accompanied by a 65% decrease in hepatic blood flow, most probably caused by almost complete shunting of portal venous blood. The hepatic arterial flow appeared to be within normal limits and sufficient to cover the oxygen demand of the liver; to judge from the splanchnic elimination rate of galactose, the hemodynamic changes did not affect the functional capacity of the liver.     

Endothelial dysfunction in the regulation of cirrhosis and portal hypertension

Portal hypertension is caused by an increased intrahepatic resistance, a major consequence of cirrhosis. Endothelial dysfunction in liver sinusoidal endothelial cells (LSECs) decreases the production of vasodilators, such as nitric oxide, and favours vasoconstriction. This contributes to an increased vascular resistance in the intrahepatic/sinusoidal microcirculation and develops portal hypertension. Portal hypertension, in turn, causes endothelial dysfunction in the extrahepatic, i.e. splanchnic and systemic, circulation. Unlike dysfunction in LSECs, endothelial dysfunction in the splanchnic and systemic circulation causes overproduction of vasodilator molecules, leading to arterial vasodilation. In addition, portal hypertension leads to the formation of portosystemic collateral vessels. Both arterial vasodilation and portosystemic collateral vessel formation exacerbate portal hypertension by increasing the blood flow through the portal vein. Pathological consequences, such as oesophageal varices and ascites, result. While the sequence of pathological vascular events in cirrhosis and portal hypertension has been elucidated, the underlying cellular and molecular mechanisms causing endothelial dysfunctions are not yet fully understood. This review article summarizes the current cellular and molecular studies on endothelial dysfunctions found during the development of cirrhosis and portal hypertension with a focus on the intra‐ and extrahepatic circulations. The article ends by discussing the future directions of the study for endothelial dysfunction.     

Chronic hepatic encephalopathy in cirrhotic patients and spontaneous portacaval anastomosis. Portal angiographic and manometric study

Portal angiographic and manometric studies were prospectively carried out in 9 cirrhotic patients with spontaneous chronic portal-systemic encephalopathy. Hepatic encephalopathy presented as coma in 8 patients, and was the first manifestation of chronic liver disease in 6 cases. Hemodynamic studies showed a) a large single spontaneous portacaval anastomosis (gastrorenal, splenorenal, gradient (mean +/- SD = 16.3 +/- 5.4 mm Hg); c) a wedge hepatic venous pressure higher than portal pressure in 8 cases (difference: 1-11 mm Hg).