Hyperdynamic circulation of liver disease 40 years later: pathophysiology and clinical consequences

The gene expression of adrenomedullin, calcitonin-receptor-like receptor and receptor activity modifying proteins (RAMPs) in CCl4-induced rat liver cirrhosis

This study was undertaken to determine AM expression in carbon tetrachloride (CCl4)-induced liver cirrhosis developed with peritoneal ascites. Sprague-Dawley rats received subcutaneous injections of CCl4 twice weekly in olive oil (1:1, 0.3 ml per kg body weight) for 6 or 12 weeks until ascites developed, or saline in olive oil as control. At 6 weeks, fibrosis developed and at 12 weeks cirrhosis developed with ascites formation. At both 6 and 12 weeks, increases in plasma renin and AM were evident, as was the gene expression of AM. At 12 weeks after CCl4 injection, the gene expression of calcitonin-like-receptor (CRLR) and receptor activity modifying proteins (RAMP1, RAMP2 and RAMP3) were all elevated when compared to the control. The results suggest that liver cirrhosis increases mRNA expressions of AM, CRLR and RAMP1, RAMP2 and RAMP3 and that the increase in AM gene expression precedes the development of cirrhosis. The increase in AM synthesis as reflected by an increase in AM gene expression, together with a lack of increase in AM peptide at both 6 and 12 weeks may suggest an elevation of AM release. Given the potent vasodilatory action of AM, the increase in the synthesis and release of AM in the cirrhotic liver may also contribute to peripheral vasodilatation in liver cirrhosis.

Overexpression of kidney neutral endopeptidase (EC 3.4.24.11) and renal function in experimental cirrhosis

Neutral endopeptidase degrades atrial natriuretic peptide (ANP) and bradykinin and may generate endothelin-1 from big-endothelin. In advanced cirrhosis, sodium retention is accompanied by elevated plasma ANP levels, and infusion of ANP causes hypotension, but in normal humans increasing the concentration of ANP through the inhibition of neutral endopeptidase, localized in renal proximal tubule cells, causes natriuresis without any arterial pressure drop. The purpose of this study was the assessment of kidney neutral endopeptidase expression and responses to candoxatrilat (a specific inhibitor of this enzyme) in rats with CCl4-induced cirrhosis. Two groups of control rats ( n = 5) were injected with vehicle or 3 mg/kg candoxatrilat. Three groups of cirrhotic rats with ascites ( n = 10) received vehicle alone or 3 or 10 mg/kg candoxatrilat. In cirrhotic rats, Western blot analysis revealed a 170% increase in renal neutral endopeptidase protein content ( P < 0.03), mainly in the proximal nephron and macula densa, and both candoxatrilat dosages increased plasma ANP levels, urinary volume, and urinary excretion of sodium, ANP, and cGMP compared with vehicle alone (all P < 0.03). Candoxatrilat (10 mg/kg) also reduced tubular solute-free water reabsorption ( P < 0.03) in cirrhotic rats, but renal blood flow, arterial pressure, and plasma renin activity were unaffected. Neutral endopeptidase inhibition has natriuretic and aquaretic actions in cirrhosis without any effect on blood pressure and kidney perfusion due to a significant overexpression of this enzyme in renal cortex.

Mild increases in portal pressure upregulate vascular endothelial growth factor and endothelial nitric oxide synthase in the intestinal microcirculatory bed, leading to a hyperdynamic state

Increased nitric oxide (NO) is the main factor leading to the hyperdynamic circulation associated with advanced portal hypertension (PHT), but the initial mechanisms and the magnitude of increase in portal pressure required to trigger NO production are not known. We addressed these issues by studying systemic and splanchnic hemodynamics and endothelial NO synthase (eNOS) and VEGF expression in rats with different degrees of portal hypertension. Portal vein ligation (PVL) performed over needles of three different calibers (16-, 18-, and 20-gauge) yielded different degrees of PHT and portosystemic shunting. Compared with sham rats, all three groups of PVL rats exhibited features of hyperdynamic circulation. Rats with minimal portal hypertension (PVL with a 16-gauge needle) showed an early increase in VEGF and eNOS expression selectively at the jejunum. Immunofluorescence showed that VEGF expression was located in highly vascularized areas of the mucosa. Inhibition of VEGF signaling markedly attenuated the increase in eNOS expression. In conclusion, mild increases in portal pressure are enough to upregulate eNOS at the intestinal microcirculation, and this occurs, at least in part, through VEGF upregulation.

Bradykinin Does Not Contribute to Peripheral Vascular Tone in Patients With Cirrhosis and Ascites

Bradykinin is an endothelium-dependent vasodilator and inflammatory mediator. The aim of the present study was to examine the effects of bradykinin on peripheral vascular tone in patients with cirrhosis and ascites. Forearm blood flow was measured using venous occlusion plethysmography in 8 patients with biopsy-proven alcohol-induced cirrhosis, ascites, and portal hypertension, and 8 age- and sex-matched healthy controls. On 1 occasion, subjects received an intrabrachial infusion of the selective bradykinin antagonist B9340 (1.5-13.5 nmol/min) followed by a control vasoconstrictor norepinephrine (60-540 pmol/min), and on another occasion bradykinin (100-900 pmol/min) followed by the endothelium-independent vasodilator, sodium nitroprusside (SNP, 2-8 microg/min). Bradykinin and SNP caused a dose-dependent vasodilatation (P < 0.001 for both) that did not differ between the 2 groups. Although norepinephrine caused a similar dose-dependent vasoconstriction in both groups (P < 0.001), B9340 had no effect on forearm blood flow in either group (at 13.5 nmol/min in patients; -5%, 95% CI -13-3). Bradykinin does not provide a major contribution to the maintenance of peripheral vascular tone in patients with cirrhosis and ascites. Our findings also suggest that, in contrast to cardiovascular disease, patients with liver cirrhosis do not have marked endothelial dysfunction.

Adrenal insufficiency in patients with cirrhosis, severe sepsis and septic shock

Patients with cirrhosis are susceptible to bacterial infection, which can result in circulatory dysfunction, renal failure, hepatic encephalopathy, and a decreased survival rate. Severe sepsis is frequently associated with adrenal insufficiency, which may lead to hemodynamic instability and a poor prognosis. We evaluated adrenal function using short corticotropin stimulation test (SST) in 101 critically ill patients with cirrhosis and severe sepsis. Adrenal insufficiency occurred in 51.48% of patients. The patients with adrenal insufficiency had a higher hospital mortality rate when compared with those with normal adrenal function (80.76% vs. 36.7%, P < .001). The cumulative rates of survival at 90 days were 15.3% and 63.2% for the adrenal insufficiency and normal adrenal function groups, respectively (P < .0001). The hospital survivors had a higher cortisol response to corticotropin (16.2 +/- 8.0 vs. 8.5 +/- 5.9 microg/dL, P < .001). The cortisol response to corticotropin was inversely correlated with various disease severity, Model for End-Stage Liver Disease, and Child-Pugh scores. Acute physiology, age, chronic health evaluation III score, and cortisol increment were independent factors to predict hospital mortality. Mean arterial pressure on the day of SST was lower in patients with adrenal insufficiency (60 +/- 14 vs. 74.5 +/- 13 mm Hg, P < .001), and a higher proportion of these patients required vasopressors (73% vs. 24.48%, P < .001). Mean arterial pressure, serum bilirubin, vasopressor dependency, and bacteremia were independent factors that predicted adrenal insufficiency. In conclusion, adrenal insufficiency is common in critically ill patients with cirrhosis and severe sepsis. It is related to functional liver reserve and disease severity and is associated with hemodynamic instability, renal dysfunction, and increased mortality.

Spontaneous baroreflex cardiac sensitivity in end-stage liver disease: effect of liver transplantation

BACKGROUND AND OBJECTIVE

End-stage liver disease is associated with an imbalance in the autonomic nervous system. The purpose of this study was to estimate the effect of liver transplantation on this imbalance.

METHOD

The study involved 10 patients undergoing liver transplantation and 9 patients without liver impairment undergoing liver surgery. The spontaneous baroreflex sensitivity was measured before and 1 month after surgery for the liver surgery group; before and 1, 3, 6, 12 and 18 months after orthotopic liver transplantation.

RESULTS

The spontaneous baroreflex slope of patients with end-stage liver disease was decreased before liver transplantation compared to the liver surgery group (3.9 +/- 2.5 ms mmHg(-1) vs. 9.9 +/- 5.0 ms mmHg(-1), P = 0.002). The mean slope was significantly increased at 12 and 18 months compared to the pre-transplantation value (3.9 +/- 2.5 ms mmHg(-1) vs. 8.1 +/- 6.6 ms mmHg(-1) and 7.4 +/- 4.8 ms mmHg(-1), respectively; P = 0.042). Nevertheless, further analysis of individual data showed that only four patients exhibited a marked increase in their baroreflex slope 12 months after the liver transplantation whereas it remained decreased in the six others.

CONCLUSIONS

These results confirm that the baroreflex sensitivity is depressed in end-stage liver disease in line with an autonomic nervous system imbalance. The liver transplantation reverses this disturbance only in some patients.

Defective RhoA/Rho-kinase signaling contributes to vascular hypocontractility and vasodilation in cirrhotic rats

BACKGROUND & AIMS

Portal hypertension is associated with arterial hypotension and vascular hypocontractility, which persists despite elevated plasma levels of vasoconstrictors. We investigated the role of the RhoA/Rho-kinase pathway in vascular smooth muscle hypocontractility of rats with secondary biliary cirrhosis.

METHODS

Aortic expressions of RhoA and Rho-kinase were analyzed in sham-operated and BDL rats by reverse-transcription polymerase chain reaction (RT-PCR) and immunoblots. Activation of aortic RhoA was examined by pull down of guanosine triphosphate (GTP)-RhoA and membrane translocation of RhoA. Rho-kinase activity was assessed as phosphorylation of its substrate, moesin. Contractility of isolated aortic rings was determined myographically. The hemodynamic effect of the Rho-kinase inhibitor (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632) was determined in vivo by measuring changes in mean arterial pressure and systemic vascular resistance (SVR) (microspheres).

RESULTS

Contraction of aortic rings from BDL rats was impaired in response to the alpha(1)-adrenergic receptor agonist methoxamine but not to high molar KCl. Aortic expression of RhoA was unchanged in cirrhotic rats, whereas Rho-kinase was down-regulated posttranscriptionally. Methoxamine-induced activation of RhoA as well as basal and methoxamine-induced phosphorylation of moesin were strongly reduced in aortas from cirrhotic rats. Aortic rings from cirrhotic rats precontracted with methoxamine showed an increased sensitivity to relaxation with Y-27632. The drop in SVR induced by Y-27632 was larger in cirrhotic rats than in sham-operated rats.

CONCLUSIONS

An impaired vascular activation of RhoA and a down-regulation of Rho-kinase might contribute to vasodilation and vascular hypocontractility in BDL-induced cirrhosis.

Perméabilité intestinale et cirrhose

Patients with cirrhosis are at increased risk of developing infections due to bacterial translocation. This process depends on three principal factors: bacterial overgrowth, immunodepression, and altered intestinal permeability. Intestinal barrier functions may be disturbed in cirrhosis, related to the toxic effects of alcohol (on mucosa and biological membranes) and portal hypertensive enteropathy. Few studies on the assessment of intestinal permeability in cirrhotic patients are available, and contradictory results may be explained by methodological differences. However, four studies using a differential sugar absorption test (lactulose-mannitol test, a combination of an oligosaccharide and a monosaccharide) showed an increased intestinal permeability in cirrhotic patients. The recurrence of spontaneous bacterial peritonitis can be appreciated only by one similar case history, a low rate of protides in ascites (<10 g/L), bilirubinemia > 55 micromol/L, and thrombocytopenia<98.000/mm3. These results suggest that primary antibiotherapy prophylaxis should be recommended, but this recommendation is limited by the risk of bacterial resistant selection and by the fact that no patient survival benefits was shown. Intestinal permeability could be another predictive factor to justify preventive antibiotherapy; but more studies are needed and methods should be standardized (technique used to measure permeability, patient groups involved).

Cardiac and vascular changes in cirrhosis: Pathogenic mechanisms

Cardiovascular abnormalities accompany both portal hypertension and cirrhosis. These consist of hyperdynamic circulation, defined as reduced mean arterial pressure and systemic vascular resistance, and increased cardiac output. Despite the baseline increased cardiac output, ventricular inotropic and chronotropic responses to stimuli are blunted, a condition known as cirrhotic cardiomyopathy. Both conditions may play an initiating or aggravating pathogenic role in many of the complications of liver failure or portal hypertension including ascites, variceal bleeding, hepatorenal syndrome and increased postoperative mortality after major surgery or liver transplantation. This review briefly examines the major mechanisms that may underlie these cardiovascular abnormalities, concentrating on nitric oxide, endogenous cannabinoids, central neural activation and adrenergic receptor changes. Future work should address the complex interrelationships between these systems.

The hyperdynamic circulation of chronic liver diseases: from the patient to the molecule

The hyperdynamic circulatory syndrome observed in chronic liver diseases is a great example of research that originated from clinical observations and progressed in the last 50 years from the patient to the experimental laboratory. Our knowledge has evolved from the patient to the molecule, using experimental models that serve as a source for understanding the complex pathophysiological mechanisms that govern this complex syndrome. We now know that progressive vasodilatation is central to the detrimental effects observed in multiple organs. Although nitric oxide has been shown to be the primary vasodilator molecule in these effects, other molecules also participate in the complex mechanisms of vasodilatation. This review summarizes three major areas: first, clinical observation in patients; second, experimental models used to study the hyperdynamic circulatory syndrome; and third, the vasodilator molecules that play roles in vascular abnormalities observed in portal hypertension.

Cardiopulmonary complications in chronic liver disease

Patients with cirrhosis and portal hypertension exhibit characteristic cardiovascular and pulmonary hemodynamic changes. A vasodilatatory state and a hyperdynamic circulation affecting the cardiac and pulmonary functions dominate the circulation. The recently defined cirrhotic cardiomyopathy may affect systolic and diastolic functions, and imply electromechanical abnormalities. In addition, the baroreceptor function and regulation of the circulatory homoeostasis is impaired. Pulmonary dysfunction involves diffusing abnormalities with the development of the hepatopulmonary syndrome and portopulmonary hypertension in some patients. Recent research has focused on the assertion that the hemodynamic and neurohumoral dysregulation are of major importance for the development of the cardiovascular and pulmonary complications in cirrhosis. This aspect is important to take into account in the management of these patients.

Modelos animales en el estudio de la hipertensión portal

Animal models allow detailed study of the hemodynamic alterations in portal hypertension syndrome and of the molecular mechanisms involved in the abnormalities in splenic and systemic circulation associated with this syndrome. Models of prehepatic portal hypertension can be used to study alterations in the splenic circulation and the physiopathology of hyperdynamic circulation. Moreover, models of cirrhosis allow the alterations in intrahepatic microcirculation that lead to increased resistance to portal flow to be studied. The present review summarizes currently available animal models of portal hypertension and analyzes their relative utility in investigating the distinct disorders associated with this entity. The criteria for the choice of a particular model, depending on the specific objectives of the study, are also discussed.

Chronic administration of propylthiouracil ameliorates hyperdynamic circulation in portal hypertensive rats

OBJECTIVE

To evaluate the effect of a hypothyroid state, induced by chronic propylthiouracil administration, on splanchnic and systemic hemodynamic parameters in rats with portal hypertension due to portal vein ligation.

METHODS

Portal hypertension was induced by surgical stenosis of the portal vein. Cardiac index and portal blood flow were measured using radioactive microspheres. Measurements were performed after treatment with propylthiouracil (1 mg/ml in drinking water) for 5 days.

RESULTS

Propylthiouracil-treated portal hypertensive rats had a lower portal pressure (12.4 +/- 1.9 versus 16.3 +/- 0.7 mmHg; p < 0.05) and portal blood flow (11.6 +/- 0.7 versus 13.2 +/- 1.3 ml/min/100 g; p < 0.05) than non-treated animals. Splanchnic vasoconstriction in treated animals was associated with a higher peripheral vascular resistance (2.3 +/- 0.4 versus 1.8 +/- 0.3 mmHg/ml/min/100 g; p < 0.05) than controls.

CONCLUSION

These results suggest that portal pressure can be lowered by inducing a hypothyroid state by chronic administration of propylthiouracil.

The management of portal hypertension

Portal hypertension is an almost unavoidable complication of cirrhosis, and it is responsible for the more lethal complications of this syndrome. Appearance of these complications represents the major cause of death and liver transplantation in patients who have cirrhosis. This article highlights treatment modalities in use for managing portal hypertension and those that may be available in the future.

Prolonged Q-T(c) interval in mild portal hypertensive cirrhosis

BACKGROUND/AIMS

The Q-T(c) interval is prolonged in a substantial fraction of patients with cirrhosis, thus indicating delayed repolarisation. However, no information is available in mild portal hypertensive patients. We therefore determined the Q-T(c) interval in cirrhotic patients with hepatic venous pressure gradient (HVPG) < 12 mmHg.

METHODS

Forty-four patients with cirrhosis and HVPG < 12 mmHg underwent a haemodynamic study. They were compared with 36 cirrhotic patients with clinically significant portal hypertension (HVPG> or = 12 mmHg) and controls without liver disease.

RESULTS

The fraction with prolonged Q-T(c) interval (> 0.440 s(1/2)) was similar in the two cirrhotic groups (49 vs 50%, ns) and significantly above that of the controls (5%, P < 0.005). Q-T(c) was normal in patients with normal HVPG. Likewise, mean Q-T(c) was 0.449 and 0.447 s(1/2) in the two cirrhotic groups (ns), values which are significantly above that of the controls (0.410 s(1/2), P < 0.01). In the mild portal hypertensive group, the Q-T(c) interval was inversely related to indicators of liver function, such as indocyanine green clearance (r = -0.34, P < 0.02).

CONCLUSIONS

Delayed repolarisation of the myocardium already occurs in a substantial fraction of patients with cirrhosis with only a mild increase in portal pressure. The prolonged Q-T(c) interval may be related to liver dysfunction and to the presence of portal hypertension.

Deoxycholyltaurine-induced vasodilation of rodent aorta is nitric oxide- and muscarinic M3 receptor-dependent

Emerging evidence indicates that some secondary bile acids interact functionally with muscarinic cholinergic receptors. Using thoracic aortic rings prepared from rats and mice, we examined the mechanism of deoxycholyltaurine-induced vasorelaxation. Increasing concentrations of both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from rat thoracic aortae. These effects were reduced by endothelial denudation and by treatment with an inhibitor of nitric oxide formation and with a synthetic acetylcholine:bile acid hybrid that acts as a muscarinic receptor antagonist. Likewise, both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 0.1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from mouse thoracic aortae. These effects were reduced by endothelial denudation, addition of an inhibitor of nitric oxide formation, and by muscarinic M(3) receptor knockout. We conclude that the systemic vasodilatory actions of deoxycholyltaurine are mediated in part by a nitric oxide-, muscarinic M(3) receptor-dependent mechanism. In advanced liver disease, interaction of serum bile acids with endothelial muscarinic receptors may explain nitric oxide overproduction in the systemic circulation and resulting peripheral arterial vasodilation.

Loss of tubuloglomerular feedback in decompensated liver cirrhosis: physiopathological implications

In healthy subjects, arterial pressure reduction or renal ischemia produces renal artery dilatation through autoregulation and tubuloglomerular feedback (TuGF). Patients with decompensated cirrhosis have reduced kidney perfusion pressure but show renal vasoconstriction instead of autoregulation-mediated vasodilation. This study investigates the consequences of kidney autoregulation loss on renal perfusion, glomerular filtration rate, and tubular handling of electrolytes in both compensated and ascitic nonazotemic cirrhotic patients. Forty-two consecutive patients with diuretic-free liver cirrhosis (32 with preascitic and 10 with ascitic disease) and 10 controls were submitted to the following determinations: (a) basal plasma renin activity and aldosterone levels; (b) endogenous dopaminergic activity measured as incremental aldosterone responses during metoclopramide administration; and (c) renal clearances of sodium, potassium, inulin, para-aminohippurate and lithium. Compared with the other groups, ascitic patients showed lower renal plasma flow (P < 0.01) and lithium clearance (P < 0.05), a higher filtration fraction (P < 0.01), and secondary aldosteronism. Controls and preascitic patients displayed tubuloglomerular feedback (the mechanism increasing the glomerular filtration rate when a reduced sodium load reaches the distal tubule), as demonstrated by negative correlations between fractional excretion of lithium (an expression of fractional delivery of sodium to the distal nephron) and glomerular filtration rate (respectively, r = -0.73, P < 0.03, and r = -0.48, P < 0.01). Conversely, patients with ascites showed a positive correlation between lithium fractional excretion and glomerular filtration rate (r = 0.64, P < 0.05). Reduction in renal perfusion, increased filtration fraction, and TuGF derangement, as found in decompensated patients, are indicative of prevalent postglomerular arteriolar vasoconstriction, with ensuing stimulation of proximal tubular sodium reabsorption.

Prognosis of Hepatocellular Carcinoma after Hepatectomy in Patients with Renal Dysfunction

We evaluated the effect of renal dysfunction on the prognosis of hepatocellular carcinoma in 224 patients who underwent hepatic resection. Survival was compared between patients with (57 patients) and without renal dysfunction (116 patients), using a creatinine clearance </=70 ml/min as the cut-off value. There were no significant differences with respect to other preoperative characteristics, operative findings, or histology between the two groups. There was also no difference in survival between the two groups after hepatic resection. However, among 132 patients with a solitary tumor measuring </=5 cm in greatest dimension, the disease-free and overall survival rates of 36 patients with renal dysfunction were significantly worse after resection than those of the patients without renal dysfunction (p = 0.04 and p = 0.0003, respectively). By multivariate analysis, renal dysfunction was an independent factor indicating a poor prognosis for disease-free and overall survival after resection of small solitary tumors (p = 0.0401 and p = 0.0031, respectively). Renal dysfunction did not affect the overall prognosis after resection of hepatocellular carcinoma, but it worsened the prognosis of patients with small solitary lesions.

Development of hypoxemia in alcoholic liver disease

The aim of this study was to investigate the arterial hypoxemia in Japanese patients with alcoholic liver disease (ALD) with regard to alcohol consumption and/or disease severity. Hypoxemia was observed in 78% patients with ALD and in all 46 patients with alcoholic liver cirrhosis (ALC) and 33 (56%) of 59 patients with noncirrhotic alcoholic liver disease (NCALD) (P < 0.0001). The partial pressure of oxygen (PaO2) was 71.1 +/- 5.2 mm Hg in ALC and 78.7 +/- 6.3 mm Hg in NCALD (P < 0.0001). The oxygen consumption in ALD was significantly higher than that in control subjects (P < 0.0001), and a high oxygen consumption was seen in 88% of the patients with ALD, in all 46 ALC patients, and in 46 (78%) of 59 NCALD patients (P < 0.01). Following abstinence from alcohol, the PaO2 and oxygen consumption significantly recovered after day 2 (P < 0.0001), whereas the prothrombin index did not change in either NCALD or ALC patients. Multivariate analysis showed that alcohol consumption and oxygen consumption were significant independent predictors of PaO2. In conclusion, the present findings suggest that increased oxygen consumption due to alcohol ingestion is principally responsible for the hypoxemia in ALD patients.

The Incidence of self-prescribed oral complementary and alternative medicine use by patients with gastrointestinal diseases

GOALS

To assess the incidence of oral complementary and alternative medicine (CAM) usage by gastroenterology patients at a single university center and compare against controls.

BACKGROUND

The public awareness and usage of CAM have increased. The use of CAM has been described in patients with functional bowel disorders; however, their role in patients with gastrointestinal disease is less clear.

STUDY

Patients attending luminal gastroenterology clinics and customers at local supermarkets completed a 30-point, structured questionnaire assessing their use of CAM.

RESULTS

A total of 1,409 subjects were recruited. The incidence of CAM use was 49.5% for inflammatory bowel disease, 50.9% for irritable bowel syndrome, 20% for general gastrointestinal diseases, and 27% for controls. Pearson's chi(2) tests showed that patients with inflammatory bowel disease (IBD) or irritable bowel syndrome were more likely to use CAM than controls (P < 0.001). Binary logistic regression analysis showed that females were more likely to take CAM than men (P < 0.05).

CONCLUSIONS

The percentage of CAM users among patients with IBD is similar to those with a functional diagnosis. Increasing numbers of IBD patients are using CAM in addition to conventional therapy. Awareness of this may prevent adverse CAM and conventional drug interactions.

Prostacyclin inhibition by indomethacin aggravates hepatic damage and encephalopathy in rats with thioacetamide-induced fulminant hepatic failure

AIM: Vasodilatation and increased capillary permeability have been proposed to be involved in the pathogenesis of acute and chronic form of hepatic encephalopathy. Prostacyclin (PGI₂) and nitric oxide (NO) are important contributors to hyperdynamic circulation in portal hypertensive states. Our previous study showed that chronic inhibition of NO had detrimental effects on the severity of encephalopathy in thioacetamide (TAA)-treated rats due to aggravation of liver damage. To date, there are no detailed data concerning the effects of PGI₂ inhibition on the severity of hepatic encephalopathy during fulminant hepatic failure.

METHODS: Male Sprague-Dawley rats weighing 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection of TAA (350 mg/(kg.d) for 3 d. Rats were divided into two groups to receive intraperitoneal injection of indomethacin (5 mg/(kg.d), n = 20) or normal saline (N/S, n = 20) for 5 d, starting 2 d before TAA administration. Severity of encephalopathy was assessed by the counts of motor activity measured with Opto-Varimex animal activity meter. Plasma tumor necrosis factor-α (TNF-α, an index of liver injury) and 6-keto-PGF_1α (a metabolite of PGI₂) levels were measured by enzyme-linked immunosorbent assay.

RESULTS: As compared with N/S-treated rats, the mortality rate was significantly higher in rats receiving indomethacin (20% vs 5%, P<0.01). Inhibition of PGI₂ created detrimental effects on total movement counts (indomethacin vs N/S: 438±102 vs 841±145 counts/30 min, P<0.05). Rats treated with indomethacin had significant higher plasma levels of TNF-α (indomethacin vs N/S: 22±5 vs 10±1 pg/mL, P<0.05) and lower plasma levels of 6-keto-PGF_1α (P<0.001), but not total bilirubin or creatinine (P>0.05), as compared with rats treated with N/S.

CONCLUSION: Chronic indomethacin administration has detrimental effects on the severity of encephalopathy in TAA-treated rats and this phenomenon may be attributed to the aggravation of liver injury. This study suggests that PGI₂ may provide a protective role in the development of fulminant hepatic failure.

Bacterial translocation and its consequences in patients with cirrhosis

Bacterial translocation is the passage of viable bacteria from the intestinal lumen to mesenteric lymph nodes and other extraintestinal sites. Spontaneous bacterial peritonitis is the main clinical consequence of bacterial translocation in cirrhosis. Translocation of bacterial products of viable or non-viable bacteria, such as endotoxin and/or bacterial DNA, through the intestinal wall could stimulate the immune system and the hyperdynamic circulatory state in cirrhosis with clinical consequences that are under evaluation. Bacterial translocation is currently considered the passage of viable gut flora across the intestinal barrier to extraluminal sites. Aerobic Gram-negative bacilli are the most common translocating bacteria. Intestinal bacterial overgrowth, impairment in permeability of the intestinal mucosal barrier, and deficiencies in local host immune defences are the major mechanisms postulated to favour bacterial translocation in cirrhosis. Bacterial translocation is a key step in the pathogenesis of spontaneous bacteraemia and spontaneous bacterial peritonitis in cirrhosis. Translocation of intestinal bacterial products from viable or non-viable bacteria, such as endotoxin and bacterial DNA, has recently been associated with pathophysiological events, such as activation of the immune system and derangement of the hyperdynamic circulatory status in cirrhosis. Clinical consequences of these effects of bacterial products are presently under investigation.

The role of vasoactive drugs in the treatment of oesophageal varices

Oesophageal varices are among the most important clinical consequences of portal hypertension. Recent progress in the knowledge of the pathophysiology of portal hypertension has led to the concept that it results from the increase of sinusoidal resistance and the increase in portal blood inflow consequent to splanchnic vasodilatation. Vasoactive drugs have therefore been evaluated, aiming to restore the imbalance between the increased intrahepatic and the decreased splanchnic vascular resistance. A large number of randomised, controlled trials have shown that vasoactive drugs in single or combination therapy, significantly reduce the risk of the first bleeding and rebleeding from oesophageal varices. Vasoactive drugs are also effective and safe in controlling acute variceal bleeding. Because of their high clinical efficacy, safety, ease of use and low cost, vasoactive drugs should be considered the first choice treatment for oesophageal varices.

Gut microflora in the pathogenesis of the complications of cirrhosis

The gut flora plays an important role in the pathogenesis of the complications of cirrhosis. Cirrhotic patients are prone to develop bacterial infections, mainly the 'spontaneous' infection of ascites or spontaneous bacterial peritonitis. Other complications of cirrhosis, such as variceal haemorrhage and ascites, occur mostly or solely as a consequence of portal hypertension. Portal pressure increases initially as a consequence of an increased intrahepatic resistance but, once collaterals have formed, high portal pressure is maintained by an increased splanchnic blood inflow secondary to vasodilatation. Splanchnic vasodilatation is the initiating event in the hyperdynamic circulatory state that aggravates the complications of cirrhosis. The gut flora plays a role in both the development of infections and in the hyperdynamic circulatory state of cirrhosis and, although less prominently, it also plays a role in the pathogenesis of hepatic encephalopathy. This chapter presents evidence regarding gut flora and its modification in the pathogenesis and management of these complications of cirrhosis.

Inappropriately low angiotensin II generation: a factor determining reduced kidney function and survival in patients with decompensated cirrhosis

BACKGROUND/AIMS

Angiotensin II contributes to the post-glomerular arteriolar vasoconstriction which maintains the glomerular filtration rate (GFR) in renal hypoperfusion. To explore whether depressed angiotensin II generation, due to reduced angiotensinogen production or low angiotensin-converting enzyme (ACE) levels, could impair kidney function in advanced cirrhosis.

METHODS

We studied and prospectively followed up 21 diuretic-free ascitic cirrhotic patients, through these determinations: plasma levels of active renin (AR), renin activity (PRA), angiotensin II, ACE and aldosterone; renal clearances of sodium, inulin and para-aminohippurate; antipyrine clearance. Fifteen healthy subjects were also studied.

RESULTS

GFR distribution was bimodal, 10 patients had low GFR values (l-GFR group) and 11 had normal-GFR values (n-GFR group) (below and above 105 ml/min per 1.73 m(2) body surface area). Antipyrine clearance and Child-Pugh score did not differ in the two patient groups. l-GFR group had higher AR and PRA values, lower ACE levels and a significantly higher AR/Angiotensin II ratio than n-GFR group (all P<0.01). All 21 patients showed increased values of the AR/PRA ratio, i.e. subnormal angiotensinogen levels (P<0.03). The 18-month survival rates of l-GFR and n-GFR groups were 20 and 81% (P<0.02).

CONCLUSIONS

Low-GFR cirrhotic patients had a worse survival rate associated with more severe contraction of the effective arterial blood volume, higher AR/Angiotensin II ratio and lower ACE levels.

Acute non-selective beta-adrenergic blockade reduces prolonged frequency-adjusted Q-T interval (QTc) in patients with cirrhosis

BACKGROUND/AIMS

Earlier studies have shown a prolonged frequency-adjusted Q-T interval (QTc>0.440 s(1/2)) in a substantial fraction of patients with cirrhosis. The effect of beta-blockade on QTc is unknown, and its determination was the aim of the study.

METHODS

Seventeen patients with cirrhosis received 80 mg propranolol orally during a haemodynamic investigation with measurements at baseline and 90 min after propranolol ingestion.

RESULTS

Beta-blockade reduced cardiac output (-21%, P<0.001), heart rate (-20%, P<0.001), and the hepatic venous pressure gradient (HVPG, -17%, P<0.02). The mean QTc=0.460 s(1/2) was prolonged compared to 0.410 s(1/2) in age-matched controls (P<0.01). Whereas QTc decreased during beta-blockade in the cirrhotic patients (from 0.460 to 0.440 s(1/2), P<0.01), no effect was found in the subgroup with normal QTc (0.429 vs. 0.422 s(1/2), ns), and a reduction was seen in the patients with prolonged QTc (from 0.488 to 0.456 s(1/2), P<0.01). The percentage decrease in QTc was related to the reduction in HVPG (r=0.48, P=0.03) and cardiac output (r=0.56, P=0.02).

CONCLUSIONS

Acute non-selective beta-blockade reduces prolonged QTc towards normal values in patients with cirrhosis. The clinical significance of QTc reduction in arrhythmia is a topic for future research.

Dynamic changes in expression of myosin phosphatase in a model of portal hypertension

Myosin phosphatase is a target for signaling pathways that modulate calcium sensitivity of force production in smooth muscle. Myosin phosphatase targeting subunit 1 (MYPT1) isoforms are generated by cassette-type alternative splicing of exons in the central and 3' portion of the transcript. Exclusion of the 3' alternative exon, coding for the leucine zipper (LZ)-positive MYPT1 isoform, is associated with the ability to desensitize to calcium (relax) in response to NO/cGMP-dependent signaling. We examined expression of MYPT1 isoforms and smooth muscle phenotype in normal rat vessels and in a prehepatic model of portal hypertension characterized by arteriolar dilation. The large capacitance vessels, aorta, pulmonary artery, and inferior vena cava expressed predominantly the 3' exon-out/LZ-positive MYPT1 isoform. The first-order mesenteric resistance artery (MA1) and portal vein (PV) expressed severalfold higher levels of MYPT1 with predominance of the 3' exon-included/LZ-negative isoform. There was minor variation in the presence of the MYPT1 central alternative exons. Myosin heavy and light chain splice variants in part cosegregated with MYPT1 isoforms. In response to portal hypertension induced by PV ligature, abundance of MYPT1 in PV and MA1 was significantly reduced and switched to the LZ-positive isoform. These changes were evident within 1 day of PV ligature and were maintained for up to 10 days before reverting to control values at day 14. Alteration of MYPT1 expression was part of a complex change in protein expression that can be generalized as a modulation from a phasic (fast) to a tonic (slow) contractile phenotype. Implications of vascular smooth muscle phenotypic diversity and reversible phenotypic modulation in portal hypertension with regards to regulation of blood flow are discussed.

Alterations in thyroid Doppler arterial resistance indices, volume and hormones in cirrhosis: relationships with splanchnic haemodynamics

The hypothesis of thyroid involvement in the haemodynamic alterations of cirrhosis was evaluated. We measured thyroid volume (thrV), free triiodiothyronine (FT3), free thyroxin (FT4), thyroid stimulating hormone (TSH), resistance index (thrRI) and pulsatility index (thrPI) in the inferior thyroid artery in 45 cirrhotic patients of different aetiologies and Child class, and in 13 healthy subjects. Portal vein velocity, flow, diameter and hepatic, splenic, and renal arterial resistance indices were also evaluated. ThrV was increased in Child-C patients (p < 0.05). FT3 was decreased in cirrhotic patients (p < 0.05), TSH and FT4 were not different. ThrPI and thrRI were increased in cirrhotic patients (thrPI: 1.01 +/- 0.15 vs. 0.81 +/- 0.11; thrRI: 0.62 +/- 0.05 vs. 0.53 +/- 0.04; p < 0.01) and were inversely correlated with FT3 (p < 0.05), and directly correlated with hepatic, splenic and renal resistance indices (p < 0.01). In conclusion, thyroid is involved, primarily and secondarily, in the haemodynamic alterations of cirrhosis; a reduction in vasodilator FT3 may play a role in the pathophysiology.

Adrenomedullin in cirrhotic and non-cirrhotic portal hypertension

AIM: Adrenomedullin (ADM) is a potent vasodilator peptide. ADM and nitric oxide (NO) are produced in vascular endothelial cells. Increased ADM level has been linked to hyperdynamic circulation and arterial vasodilatation in cirrhotic portal hypertension (CPH). The role of ADM in non-cirrhotic portal hypertension (NCPH) is unknown. plasma ADM levels were studied in patients with NCPH, compensated and decompensated cirrhosis in order to determine its contribution to portal hypertension (PH) in these groups.

METHODS: There were 4 groups of subjects. Group 1 consisted of 27 patients (F/M: 12/15) with NCPH due to portal and/or splenic vein thrombosis (mean age: 41 ± 12 years), group 2 consisted of 14 patients (F/M: 6/8) with compensated (Child-Pugh A) cirrhosis (mean age: 46 ± 4), group 3 consisted of 16 patients (F/M: 6/10) with decompensated (Child-Pugh C) cirrhosis (mean age: 47 ± 12). Fourteen healthy subjects (F/M: 6/8) (mean age: 44 ± 8) were used as controls in Group 4. ADM level was measured by ELISA. NO was determined as nitrite/nitrate level by chemoluminescence.

RESULTS: ADM level in Group 1 (236 ± 61.4 pg/mL) was significantly higher than that in group 2 (108.4 ± 28.3 pg/mL) and group 4 (84.1 ± 31.5 pg/mL) (both P < 0.0001) but was lower than that in Group3 (324 ± 93.7 pg/mL) (P = 0.002). NO level in group 1 (27 ± 1.4 μmol/L) was significantly higher than that in group 2 (19.8 ± 2.8 μmol/L) and group 4 (16.9 ± 1.6 μmol/L) but was lower than that in Group 3 (39 ± 3.6 μmol/L) (for all three P < 0.0001). A strong correlation was observed between ADM and NO levels (r = 0.827, P < 0.0001).

CONCLUSION: Adrenomedullin and NO levels were high in both non-cirrhotic and cirrhotic portal hypertension and were closely correlated, Adrenomedullin and NO levels increased proportionally with the severity of cirrhosis, and were significantly higher than those in patients with NCPH. Portal hypertension plays an important role in the increase of ADM and NO. Parenchymal damage in cirrhosis may contribute to the increase in these parameters.

Systemic and regional hemodynamics in pre-ascitic cirrhosis: effects of posture

BACKGROUND/AIMS

To clarify the hemodynamic pattern of pre-ascitic cirrhosis, we compared the impact of posture on systemic and regional hemodynamics of patients and healthy subjects without and with plasma volume expansion.

METHODS

Cardiac index (CI), peripheral vascular resistance (PVRi), heart rate, mean arterial pressure, and the mean blood flow velocities of superior mesenteric (SMAV) and common femoral arteries were evaluated by duplex-Doppler techniques in 10 patients and 20 healthy controls after 2 h of standing and 2 h after lying down. Ten healthy controls received saline infusion (15 ml/kg body weight) when they changed their posture, and five were also evaluated after plasma volume expansion in the upright posture.

RESULTS

Standing systemic and regional hemodynamics did not differ between patients and controls. After saline infusion, standing control subjects showed greater CI and SMAV than patients. Recumbency caused changes of CI, PVRi and SMAV greater in patients and controls with plasma expansion than in controls without expansion, so that supine patients and controls with expansion were indistinguishable, showing higher CI and SMAV and lower PVRi than controls without expansion.

CONCLUSIONS

Systemic and regional hemodynamics of patients with pre-ascitic cirrhosis are mainly determined by blood volume expansion which is compartmentalized within the splanchnic venous bed during standing and translocates towards the central and arterial circulatory districts during recumbency.

Expression of nitric oxide synthase isoforms in human liver cirrhosis

Several mediators of systemic vasodilatation in liver cirrhosis have been reported. Among these is nitric oxide (NO), which has been proposed as one of the main mediators. In this study, sera and liver biopsies were analysed from 15 patients with clinically and pathologically diagnosed liver cirrhosis. In addition, sera from seven and liver biopsies from three healthy controls were used. Serum levels of nitrite (the end product of NO) were measured using the Griess reaction and the expression of the inducible nitric oxide synthase (iNOS) and constitutive nitric oxide synthase (ecNOS) proteins was investigated using immunohistochemistry. This study shows that serum nitrite levels (94 +/- 9.8 micro mol/l) in cirrhotic patients were significantly (p < 0.05) increased in comparison with the controls (36.6 +/- 11.03 micro mol/l). iNOS was completely absent from the control group but was highly expressed in the livers from the cirrhotic group. iNOS was seen mainly in the inflammatory cells infiltrating the portal tracts, blood monocyte-like cells, hepatocytes, sinusoidal cells, and endothelial cells. However, expression of ecNOS was only seen in the vascular endothelial cells of both the control and the cirrhotic groups, but was much higher in the latter. It is therefore clear that NO is augmented in cirrhotic patients and it is mainly produced by induction of iNOS. Moreover, NO up-regulation is dependent on the inflammatory stage of liver cirrhosis. ecNOS production could be a normal chronic adaptation mechanism of the endothelium to the chronically increased splanchnic blood flow secondary to portal hypertension. In the near future, the appropriate inhibition of NO activity by using NOS-active agents may provide a novel strategy for the treatment of patients with liver cirrhosis.

Cardiac output determined by echocardiography in patients with cirrhosis: comparison with the indicator dilution technique

BACKGROUND/AIMS

Measurement of cardiac output in hyperkinetic patients with cirrhosis by Doppler echocardiography is increasingly reported, but has not been validated. We have compared simultaneous measurements of cardiac output by Doppler echocardiography (CO(d)) and by the indicator dilution technique (CO(I)).

METHODS

Twelve patients with cirrhosis were studied. CO(d) was measured as the spatial mean velocity of the left ventricular outflow tract, multiplied by the cross-sectional area and the heart rate. CO(I) was determined by the standard indicator dilution technique after injection of 125I albumin and 99mTc albumin into the right atrium and subsequent sampling from the femoral artery.

RESULTS

The mean CO(d) and CO(I) were similar (7.20 vs 7.15 l/min, NS). A highly significant correlation was present between CO(d) and CO(I) (r = 0.86, P < 0.0001; slope 0.91, Y(0) = 0.78 l/min). However, the mean squared difference between CO(d) and CO(I) was 2.3 (l/min)2. A Bland-Altman plot revealed no trend with the level of cardiac output. The standard deviation (0.79 vs 0.30 l/min, P < 0.01) and the coefficient of variation (10.5 vs 4.2%, P < 0.01) of duplicate measurements were significantly higher with the Doppler technique.

CONCLUSION

Doppler measurements of cardiac output in groups of patients with cirrhosis are accurate with respect to the group mean, but marked disagreements of over- and underestimation were seen in individual patients. The reproducibility of the Doppler technique is acceptable, although not as good as that of the indicator dilution technique.

Portal hypertension is associated with increased mRNA levels of vasopressor G-protein-coupled receptors in human hepatic arteries

BACKGROUND

The contractile response of human splanchnic vessels to different vasoconstrictors is attenuated in cirrhosis. Functional studies indicate a cellular signalling defect upstream of the G-protein level. The aim of the present study was to analyze expression and mRNA levels of the following most relevant vasopressor receptors in the smooth musculature of human hepatic arteries: alpha1 adrenoceptor (AR) subtypes a, b and d, angiotensin II type 1 receptor (AT1), arginine vasopressin receptor type 1a (V1a), endothelin receptor type A (ETA) and B (ETB).

MATERIALS AND METHODS

Hepatic arteries were collected from 10 donors (noncirrhotic) and 14 recipients (cirrhotic) at liver transplantations. Real-time-PCR was performed to quantify steady-state levels of receptor mRNAs.

RESULTS

alpha 1aAR mRNA levels showed no significant difference between the cirrhotic arteries and the controls while the mRNA levels of the other vasoactive receptors were significantly higher in the cirrhotic hepatic arteries (alpha 1bAR: 4-fold, P = 0.013; AT1: 16-fold, P = 0.024; V1a: 23-fold, P = 0.001; ETA: 4-fold, P = 0.02; ETB: 8-fold, P = 0.008). No mRNA for the alpha 1dAR was detected either in the donor or recipient hepatic arteries.

CONCLUSION

We conclude that vascular hyporeactivity to the most relevant endogenous vasoconstrictors of cirrhotic hepatic arteries is not caused by a receptor down-regulation at mRNA levels. In contrast they were up-regulated.

Pathogenesis of ascites and predictors of resistance to therapy

Ascites is one of the most frequent complications of cirrhosis. Its appearance is considered as the marker of the transition from the compensated to the decompensated stage of the disease. Appearance of ascites also has prognostic significance, as it causes a sharp drop in the expected survival rate. Portal hypertension is a sine qua-non for the development of ascites. Although no precise portal pressure threshold has been defined for the development of ascites, the latter rarely develops with portal pressures below 12 mmHg. In addition, in patients treated with interventions that markedly decrease portal pressure, such as surgical porta-caval shunts or transjugular intrahepatic portalsystemic shunts, a disappearance or a marked reduction of ascites can be observed. The currently most accepted theory of ascites formation is the so-called 'forward' theory. According to this theory, the development of ascites is related to the presence of severe sinusoidal portal hypertension, which causes marked splanchnic arterial vasodilation and a forward increase in the splanchnic production of lymph. Splanchnic arterial vasodilation also causes a significant reduction of the effective blood volume, leading to activation of sodium and water-retaining mechanisms. The retained sodium and water, however, while increasing total plasma volume, are unable to compensate for the reduced effective blood volume, initiating a vicious cycle. In the advanced stages of cirrhosis, the extreme underfilling of the arterial circulation leads to a maximal stimulation of the vasoconstrictor mechanisms which override the protective effect of renal vasodilator factors and cause renal vasoconstriction, further aggravating ascites and leading to functional renal insufficiency. Renal insufficiency is also one of the main causes of resistance to diuretic therapy. While several studies have investigated the predictors of survival in cirrhotic patients with ascites, this has not been done for the occurrence of resistance to therapy. However, as the mechanisms of refractoriness are associated with advanced disease and short survival, the models developed for predicting survival should be employed also to verify if they can exert such additional prediction.

Longitudinal prostaglandin E(2) generation in various organs during evolution of experimental portal hypertension

It has been suggested that the arteriolar vasodilatation and hyperdynamic circulation observed in rats with partial portal vein ligation (PPVL) is caused by increased splanchnic and systemic delivery of vasodilator substances. The aims of our study were to determine organ-specific generation of prostaglandin E(2) (PGE(2)) in rats with PPVL during the evolution of portal hypertension. Rats with PPVL and sham-operated (S) rats were studied in the first, third, fourth and 14th postoperative days. They were anesthetized and splenic pulp pressure and blood pressure were measured. Spleen, colon and lungs were removed and the splenic, pulmonary and mucosal colonic PGE(2) were determined. All PPVL rats developed sequential hemodynamic changes compatible with evolving portal hypertension. Splenic pulp pressure was higher in PPVL rats compared with S rats during all days of the study. Within the group of PPVL the splenic pulp pressure was higher in the first postoperative day and decreased in the ensuing days. No changes in splenic and colonic PGE(2) generation were noted during the study period. Pulmonary PGE(2) generation increased significantly in the first postoperative day in PPVL rats compared with S rats. However, similar increase was observed on the third postoperative day in S rats. PGE(2) probably has no role in splanchnic hemodynamic changes during evolution of portal hypertension. Pulmonary PGE(2) generation may increase as a response to increased portal pressure, or to abdominal surgery.

Dyssynchronous electrical and mechanical systole in patients with cirrhosis

BACKGROUND/AIMS

Previous investigations have shown a prolonged QT interval in some patients with cirrhosis. The aim of this study was to investigate the relation between electrical and mechanical systole in patients with different degrees of severity of cirrhosis.

METHODS

Forty-eight patients with cirrhosis and portal hypertension, studied during a haemodynamic investigation, were compared to 17 controls.

RESULTS

A prolonged QTc (above 0.440 s(1/2)) was found in 37% of the cirrhotic patients vs. 5.9% in the controls (P=0.03), and there was a correlation to liver dysfunction (P<0.02). A direct relation between QT and time of mechanical systole (tS) was observed in controls (r=0.58, P<0.01), and cirrhotic patients (r=0.44, P<0.002). In patients with a prolonged QTc interval, the difference between electrical and mechanical systole time was substantially longer than in patients with a normal QTc interval (0.078 vs. 0.031 s, P<0.005). The QT values were related to markers of hyperdynamic circulation (r=-0.48 to 0.56, P<0.05-0.001). CONCLUSIONS; Prolonged repolarization, as evidenced by prolonged QTc, is related to both impaired liver function and systemic circulatory dysfunction. In addition these patients have alterations in the cardiac excitation-contraction relation with compromised association between electrical and mechanical function.

Intestinal mucosal alterations in experimental cirrhosis in the rat: role of oxygen free radicals

Cirrhosis is associated with altered gastrointestinal function, and bacterial translocation from the gut plays an important role in the etiology of spontaneous bacterial peritonitis (SBP) seen in this condition. Although alterations in gut motility and intestinal permeability are recognized in cirrhosis, the intestinal damage at the cellular and subcellular levels is not well understood. This study looked at the mucosal alterations in experimental cirrhosis and the role of oxygen free radicals in this process. It was shown that cirrhosis results in oxidative stress in the intestine, as seen by increased xanthine oxidase (XO) activity and altered antioxidant status. Cirrhosis also affects enterocyte mitochondrial function, as assessed by respiratory control ratio, swelling, and calcium flux. Increased lipid peroxidation of the brush border membranes (BBMs) was seen along with altered intestinal transport. In conclusion, this study shows that intestinal mucosal alterations are seen in experimental cirrhosis and are possibly mediated by oxidative stress.

Adenosine A(2A) receptors in portal hypertension: their role in the abnormal response to adenosine of the cranial mesenteric artery in rabbits

1. Adenosine is a regulator of mesenteric vasodilation involved in auto-regulation and post-prandial hyperemia, but the adenosine receptor subtype involved in this relaxant effect is poorly characterized. We have now pharmacologically characterized this receptor in rabbit mesenteric arteries and investigated how this adenosine receptor response changes in portal hypertensive animals since the adenosine response is decreased. 2. The closest non-metabolisable adenosine analogue, 2-chloroadenosine (CADO), the mixed A(1)/A(2) receptor agonist, 5'-ethylcarboxamidoadenosine (NECA), and the selective A(2A) receptor agonist, 2-[4-(2-p-carbonyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680) (1 pM -- 1 mM) relaxed noradrenaline pre-contracted arteries with a rank order of potency of CGS 21680 (EC(50)=20 nM) > or = NECA (60 nM)>>CADO (640 nM). 3. The selective A(2A) receptor antagonist, 4-(2-[7-amino-2-(2-furyl)-[1,2,4]-triazolo[2,3-a][1,3,5]-triazin-5-ylamino]ethyl)phenol (ZM 241385, 100 nM), shifted to the right the CADO concentration-response curve. 4. In portal hypertensive animals, there was mainly a decreased potency but also a decreased efficacy of all tested adenosine agonists compared to normal animals. Concomitantly, there was a decreased adenosine plasma level and a decreased binding density of [(3)H]-CGS 21680 and [(3)H]-ZM 241385 to mesenteric artery membranes from portal hypertensive compared to normal rabbits. 5. These results indicate that A(2A) receptor activation is required for the adenosine-induced mesenteric relaxation and that the decreased density of A(2A) receptors may contribute to the decreased relaxation induced by adenosine of mesenteric arteries in portal hypertensive animals.