Endothelin-3 like immunoreactivity in plasma of patients with cirrhosis of the liver

The future treatment of portal hypertension

Increased understanding of the hyperdynamic circulation syndrome has resulted in novel therapeutic approaches, some of which have already reached clinical practice. Central to the hyperdynamic circulation syndrome is an imbalance between the increase in different vasodilators (foremost among which is nitric oxide) and the compensatory increase in vasoconstrictors--usually accompanied by a blunted response. This chapter discusses the role of endothelin in the pathogenesis of the syndrome and in future treatment approaches. A relatively new area of research in this field is the role of infection and inflammation in the initiation and maintenance of the hyperdynamic circulation syndrome. The use of antibiotics in the setting of acute variceal bleeding is standard practice. Studies have suggested that chronic manipulation of the intestinal flora could have beneficial effects in the treatment of portal hypertension. The bile salts are another novel and interesting target. Although their vasoactive properties have been known for some time, recent data demonstrate that their effects could be central in the pathogenesis of the hyperdynamic circulation syndrome, and that manipulation of the composition of the bile acid pool could be a therapeutic approach to portal hypertension. Finally, hypoxia and angiogenesis play a role in the development of portal hypertension and the formation of collaterals. This role needs to be further defined but it appears likely that this phenomenon is yet another target for therapeutic intervention.

Ursodeoxycholic acid reduces increased circulating endothelin 2 in primary biliary cirrhosis

BACKGROUND

Endothelins and nitric oxide regulate sinusoidal blood flow and the perfusion of the peribiliary vascular plexus.

AIMS

To study the serum and hepatic vein concentration of ET-1, ET-2, ET-3 and nitric oxide in patients with primary biliary cirrhosis and the effect of ursodeoxycholic acid treatment.

METHODS

Endothelins and nitrites/nitrates were measured in serum and hepatic vein blood in primary biliary cirrhosis and viral cirrhotic patients prior and after ursodeoxycholic acid therapy and in serum in controls. Endothelins were measured with commercial enzyme-linked immunosorbent assays and nitrites/nitrates with a modification of Griess reaction.

RESULTS

The ET-1 and ET-3 levels were similar in patients and controls. Primary biliary cirrhosis patients had the highest serum ET-2 (P < 0.001) compared with other groups. Nitrites/nitrates was increased in primary biliary cirrhosis (P < 0.05) compared with normal. ET-2 and nitric oxide were similar in all primary biliary cirrhosis stages. Ursodeoxycholic acid significantly decreased ET-2 in all stages (I and II: P < 0.05 and III and IV: P < 0.01) and increased nitric oxide (P < 0.05) in early primary biliary cirrhosis. Hepatic vein ET-1 and ET-3 were higher in viral cirrhosis patients, but only in primary biliary cirrhosis a significant difference for ET-1 and ET-3 between hepatic and peripheral veins was found.

CONCLUSIONS

Increased ET-2 is an early defect in primary biliary cirrhosis that is significantly reduced by the ursodeoxycholic acid treatment. The possibility of a more generalized endothelial cell dysfunction in primary biliary cirrhosis requires further investigation.

Effects of ET-A receptor blockade on eNOS gene expression in chronic hypoxic rat lungs

We tested the hypothesis that pulmonary endothelial nitric oxide synthase (eNOS) gene expression is primarily regulated by hemodynamic factors and is thus increased in rats with chronic hypoxic pulmonary hypertension. Furthermore, we examined the role of endothelin (ET)-1 in this regulatory process, since ET-1 is able to induce eNOS via activation of the ET-B receptor. Therefore, chronic hypoxic rats (10% O(2)) were treated with the selective ET-A receptor antagonist LU-135252 (50 mg x kg(-1) x day(-1)). Right ventricular systolic pressure and cross-sectional medial vascular wall area of pulmonary arteries rose significantly, and eNOS mRNA levels increased 1.8- and 2.6-fold after 2 and 4 wk of hypoxia, respectively (each P < 0.05). Pulmonary ET-1 mRNA and ET-1 plasma levels increased significantly after 4 wk of hypoxia (each P < 0.05). LU-135252 reduced right ventricular systolic pressure, vascular remodeling, and eNOS gene expression in chronic hypoxic rats (each P < 0.05), whereas ET-1 production was not altered. We conclude that eNOS expression in chronic hypoxic rat lungs is modified predominantly by hemodynamic factors, whereas the ET-B receptor-mediated pathway and hypoxia seem to be less important.

The NO donor molsidomine reduces endothelin-1 gene expression in chronic hypoxic rat lungs

We investigated the effects of the nitric oxide (NO) donor molsidomine and the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) on pulmonary endothelin (ET)-1 gene expression and ET-1 plasma levels in chronic hypoxic rats. Two and four weeks of hypoxia (10% O2) significantly increased right ventricular systolic pressure, the medial cross-sectional vascular wall area of the pulmonary arteries, and pulmonary ET-1 mRNA expression (2-fold and 3.2-fold, respectively). ET-1 plasma levels were elevated after 4 wk of hypoxia. In rats exposed to 4 wk of hypoxia, molsidomine (15 mg x kg(-1) x day(-1)) given either from the beginning or after 2 wk of hypoxia significantly reduced pulmonary hypertension, pulmonary vascular remodeling, pulmonary ET-1 gene expression, and ET-1 plasma levels. L-NAME administration (45 mg x kg(-1) x day(-1)) in rats subjected to 2 wk of hypoxia did not modify these parameters. Our findings suggest that in chronic hypoxic rats, exogenously administered NO acts in part by suppressing the formation of ET-1. In contrast, inhibition of endogenous NO production exerts only minor effects on the pulmonary circulation and pulmonary ET-1 synthesis in these animals.

Effects of exogenous endothelin-1 application on liver perfusion in native and transplanted porcine livers

PURPOSE

This study was designed to assess and differentiate the impact of progressivly increasing portal venous endothelin-1 (ET) plasma concentrations on hepatic micro- and macroperfusion of native porcine livers (Group A) and liver grafts after experimental transplantation (Group B).

METHODS

A standardized gradual increment in systemic ET plasma concentration (0-58 pg/ml) was induced by continuous ET-1 infusion into the portal vein in both groups (A: n = 10, B: n = 10). Control animals received only saline (n = 5, each group). Hepatic microcirculation (HMC) was quantified by thermodiffusion electrodes, hepatic artery flow (HAF), and portal venous flow (PVF) by Doppler flowmetry.

RESULTS

No changes in ET or perfusion parameters were observed in controls. The mean ET level after orthotopic liver transplantation (OLT) in Group B was elevated (baseline: 3.8 +/- 2.4 pg/ml) compared with Group A (2.8 +/- 1.9 pg/ml). With rising ET levels HAF decreased progressively in Group A from 205 +/- 97 (baseline) to 160 +/- 72 ml/min, and in Group B from 161 +/- 87 to 146 +/- 68 ml/min. PVF decreased in Group A from 722 +/- 253 to 370 +/- 198 ml/min, and in Group B from 846 +/- 263 to 417 +/- 203 ml/min. Baseline HMC in Group A was 86 +/- 15 and decreased significantly to 29 +/- 9 ml/100 g/min, and baseline MC in Group B was 90 +/- 22 and decreased to 44 +/- 32 ml/100 g/min. No significant alteration in systemic circulation was noted at the ET concentrations investigated.

CONCLUSIONS

Significant impairment of hepatic micro- and macrocirculation was detected after induction of systemic ET levels above 9.4 pg/ml both in native and in transplanted livers. Disturbance of HMC was caused predominantly by reduction of portal venous flow, while the effect of ET on HAF was less pronounced. Characteristics of flow impairment in transplanted and native livers were analogous after short cold ischemic graft storage (6 h).

High-frequency oscillatory ventilation does not decrease endothelin release in lung-lavaged rabbits

High-frequency oscillatory ventilation (HFO) has been shown to reduce lung injury and pulmonary arterial pressure (PAP). We hypothesized that HFO leads to decreased endothelin 1 (ET-1) and endothelin 3 (ET-3) release when compared to conventional mechanical ventilation (CMV) in lung-lavaged rabbits.

DESIGN

Prospective, randomized, controlled animal study. In 26 adult New Zealand White Rabbits ventilated by CMV or HFO under hypoxemic and normoxemic conditions after lung lavage (CMV-hypo: n = 5; CMV-normo: n = 8; HFO-hypo: n = 7; HFO-normo: n = 6) we recorded systemic and PAP, measured blood gases, ET-1 and ET-3 and calculated intrapulmonary venous admixture during a 4-h experiment. ET-1 was significantly increased after lavage (p < 0.05) with no further increase until the end of the experiment. Neither pulmonary arterial nor systemic arterial ET-1 differed between CMV and HFO or between hypoxemia and normoxemia. Systemic arterial ET-3, however, was significantly higher in HFO-hypo than in the other two groups ventilated under normoxemic conditions at the end of the experiment (HFO-hypo vs. CMV-normo, p < 0.05; HFO-hypo vs. HFO-normo, p < 0.05). PAP showed a continuous increase in all groups (p < 0.05). We did not find any correlation between PAP and ET-1 or ET-3. Intrapulmonary venous admixture increased in animals ventilated under hypoxemic conditions, whereas it decreased after lung lavage in those ventilated under normoxemic conditions until the end of the experiment (HFO-normo, p < 0.05).

CONCLUSIONS

This study suggests that HFO does not decrease ET-1 and ET-3 release compared to CMV in lung-lavaged rabbits. Hypoxemia, however, may increase ET-3 release from the lungs, leading to an increased intrapulmonary shunt.

Hepatic blood flow and splanchnic oxygen consumption in patients with liver failure. Effect of high-volume plasmapheresis

Liver failure represents a major therapeutic challenge, and yet basic pathophysiological questions about hepatic perfusion and oxygenation in this condition have been poorly investigated. In this study, hepatic blood flow (HBF) and splanchnic oxygen delivery (DO2, sp) and oxygen consumption (VO2,sp) were assessed in patients with liver failure defined as hepatic encephalopathy grade II or more. Measurements were repeated after high-volume plasmapheresis (HVP) with exchange of 8 to 10 L of plasma. HBF was estimated by use of constant infusion of D-sorbitol and calculated according to Fick's principle from peripheral artery and hepatic vein concentrations. In 14 patients with acute liver failure (ALF), HBF (1.78 +/- 0.78 L/min) and VO2,sp (3.9 +/- 0.9 mmol/min) were higher than in 11 patients without liver disease (1.07 +/- 0.19 L/min, P <.01) and (2.3 +/- 0.7 mmol/min, P <.001). In 9 patients with acute on chronic liver disease (AOCLD), HBF (1.96 +/- 1.19 L/min) and VO2,sp (3.9 +/- 2.3 mmol/min) were higher than in 18 patients with stable cirrhosis (1.00 +/- 0.36 L/min, P <.005; and 2.0 +/- 0.6 mmol/min, P <.005). During HVP, HBF increased from 1.67 +/- 0.72 to 2.07 +/- 1.11 L/min (n=11) in ALF, and from 1.89 +/- 1.32 to 2.34 +/- 1.54 L/min (n=7) in AOCLD, P <.05 in both cases. In patients with ALF, cardiac output (thermodilution) was unchanged (6.7 +/- 2.5 vs. 6.6 +/- 2.2 L/min, NS) during HVP. Blood flow was redirected to the liver as the systemic vascular resistance index increased (1,587 +/- 650 vs. 2, 020 +/- 806 Dyne. s. cm-5. m2, P <.01) whereas splanchnic vascular resistance was unchanged. In AOCLD, neither systemic nor splanchnic vascular resistance was affected by HVP, but as cardiac output increased from 9.1 +/- 2.8 to 10.1 +/- 2.9 L/min (P <.01) more blood was directed to the splanchnic region. In all liver failure patients treated with HVP (n=18), DO2,sp increased by 15% (P <.05) whereas VO2,sp was unchanged. Endothelin-1 (ET-1) and ET-3 were determined before and after HVP. Changes of ET-1 were positively correlated with changes in HBF (P <.005) and VO2,sp (P <.05), indicating a role for ET-1 in splanchnic circulation and oxygenation. ET-3 was negatively correlated with systemic vascular resistance index before HVP (P <.05) but changes during HVP did not correlate. Our data suggest that liver failure is associated with increased HBF and VO2, sp. HVP further increased HBF and DO2,sp but VO2,sp was unchanged, indicating that splanchnic hypoxia was not present.

Endothelin and other mediators in the pathophysiology of portal hypertension

Hyperdynamic circulation as well as increased hepatic resistance contribute to portal hypertension in cirrhosis of the liver [1]. Hyperdynamic circulation with increased cardiac output, heart rate and plasma volume and decreased arterial blood pressure and systemic <i>vasodilatation</i> is pivotal for the hyperdynamic circulation. This has prompted intense research of a number of endogenous neurohumoral mediators with vasodilating properties (NO, natriuretic peptides, glucagon, etc.) [2, 3].

Endothelin-stimulated nitric oxide production in the isolated Kupffer cell

Endothelin (ET) is a potent peptide mediator exhibiting a wide variety of effects in both the parenchymal and nonparenchymal hepatic cells. In the Kupffer cell, ET activates several transmembrane signaling pathways to generate numerous second messengers including the phospholipase C-generated products inositol-1,4,5-trisphosphate and diacylglycerol and the cyclooxygenase product prostaglandin E2 via specific ETB-type receptors. In addition to these findings, we have now demonstrated that endothelin stimulates the production of nitric oxide (NO) in the Kupffer cell in a time- and concentration-dependent manner. Western blot analysis indicates that ET-stimulated NO production occurs though activation of the inducible form of the nitric oxide synthase enzyme. These findings have important implications as the stimulation of NO production by ET may be part of the physiological response to inflammation or infection. Elevated levels of ET and NO have been found to be associated with numerous hepatic pathophysiological conditions that may contribute to derangements in the vascular system seen in these conditions.

Daily profile of plasma endothelin-1 and -3 in pre-ascitic cirrhosis: relationships with the arterial pressure and renal function

BACKGROUND/AIMS

Measurements of plasma endothelin-1 and -3 in pre-ascitic cirrhosis have provided controversial results. Similarly, the role of the endothelin system in the pathogenesis of volume and hemodynamic disturbances of cirrhosis is still debated. To provide a further insight into this issue, we assessed the daily fluctuations of plasma endothelins and their relationship with arterial pressure and renal function in pre-ascitic cirrhosis.

METHODS

Endothelin-1 and -3, plasma renin activity, atrial natriuretic peptide, noradrenaline and mean arterial pressure were measured at 11 pm, 7 am, 9 am and 6 pm in 10 patients with pre-ascitic cirrhosis and in 10 healthy subjects on normal sodium diet and carrying on their usual activities (supine from 10 pm to 7 am, standing and mobile after 7 am). Glomerular filtration rate and daily renal sodium excretion were assessed during the supine period, and from 7 am to 12 am and from 12 am to 10 pm during the standing period.

RESULTS

Endothelin-1 was higher in patients than in control subjects (p=0.000) and did not change during the study. Endothelin-3 was also higher in patients (p=0.002) and showed slight fluctuation in control subjects. The mean daily level of plasma renin activity was lower (p=0.016) and that of atrial natriuretic peptide higher (p=0.000) in patients with cirrhosis. Norepinephrine and mean arterial pressure did not differ significantly between the two groups. No correlations were found between endothelins and either hemodynamic or neuro-hormonal and renal function parameters in the two groups.

CONCLUSIONS

Despite the presence of increased effective volemia (as suggested by the reduced plasma renin activity and elevated atrial natriuretic peptide) and normal adrenergic tone, patients with pre-ascitic cirrhosis show elevated levels of endothelin-1 and endothelin-3 throughout the day. In early cirrhosis circulating endothelins, although elevated, do not appear to play a more prominent role in setting arterial pressure than in normal subjects, and endothelin elevation is not detrimental to renal function.

Endothelins in chronic liver disease

This review describes recent progress in the accumulation of knowledge about the endothelins (ETs), a family of vasoactive 21-amino acid polypeptides, in chronic liver disease. Particular prominence is given to the dynamics of ET-1 and ET-3 and their possible relation to the disturbed circulation and neurohumoral dysregulation found in cirrhosis. Recent studies have shown that the ET system is highly activated in most cirrhotic patients. Circulating ET-1 and ET-3 levels have a positive relation to the severity of the disease and fluid retention, with the highest values recorded in patients with functional renal failure. Studies on liver biopsies have revealed synthesis of ET-1 in hepatic endothelial and other cells, and recent investigations have identified the hepatosplanchnic system as a major source of ET-1 and ET-3 spillover into the circulation, with a direct relation to portal venous hypertension. In addition, marked associations with disturbance of systemic haemodynamics and with abnormal distribution of blood volume have been reported. Although the pathophysiological importance of the ET system in chronic liver disease is not completely understood, similarities to other vasopressive and antinatriuretic regulatory systems (i.e. the sympathetic nervous system, renin-angiotensin-aldosterone and vasopressin) are apparent, with respect to kinetics and haemodynamic dysregulation. Cirrhosis seems to be a pathophysiological condition with indications of the occurrence of ETs, not only as local modulators, but also as a system with potential importance for systemic regulation.

Plasma endothelin-1 and -3 in cirrhosis: relationship with systemic hemodynamics, renal function and neurohumoral systems

BACKGROUND/AIMS

The postural change from upright to supine is a physiological maneuvre which increases central blood volume. This model was used to investigate the effects of changes in effective volemia on plasma endothelin-1 and -3 concentrations in cirrhosis.

METHODS

Plasma endothelin concentrations, measured by radio-immunoassay, were determined in 20 patients with cirrhosis, 10 of whom has ascites, and nine healthy control subjects, in the upright posture and 30, 60 and 120 min after the assumption of the supine position.

RESULTS

In the upright posture, endothelin-1 was 8.9 +/- 0.4 pg/ml and endothelin-3 3.7 +/- 0.6 (mean +/- SEM) pg/ml in control subjects. Endothelin-1 was increased only in patients with ascites (12.7 +/- 1.4 pg/ml, p < 0.05; patients without ascites: 9.7 +/- 0.7 pg/ml), while endothelin-3 was elevated in both patients with and without ascites (8.0 +/- 1.5 pg/ml, p < 0.01; 5.9 +/- 0.5 pg/ml, p = 0.01, respectively). In the supine position, no significant changes in endothelin-1 or -3 occurred either in patients with ascites or in controls throughout the observation period, while a reduction in endothelin-3 was found in compensated patients after 30 and 60 min. In patients, we found negative correlations between endothelin-3, but not endothelin-1, and mean arterial pressure, both in upright (r = -0.59; p < 0.01) and supine (r = -0.56; p = 0.01) positions, atrial natriuretic factor (r = 0.50; p < 0.05) and plasma renin activity (r = 0.67; p = 0.001) in the supine position alone. In patients with ascites, endothelin-1 was inversely correlated with both glomerular filtration rate (upright: r = -0.62; p = 0.06; supine: r = -0.71, p < 0.05) and renal sodium excretion (upright: r = -0.82; p < 0.01; supine: r = -0.88; p < 0.001).

CONCLUSIONS

Plasma endothelin-1 and -3 were increased in cirrhosis with ascites, while, in pre-ascitic cirrhosis, only endothelin-3 was increased in the upright posture. Although increased endothelin-3 was associated with features suggesting a reduced effective volemia, it is likely that other mechanisms than hypovolemia were mainly responsible for high plasma endothelin levels. Increased endothelin production may play a role in circulatory and renal function abnormalities of advanced cirrhosis.

Relation of endothelins to volume regulating neurohumoral systems in patients with cirrhosis of the liver

The aim of the present study was to investigate the relationship between ET plasma concentrations and other hormonal systems in acute volume regulation of patients with cirrhosis. Ten healthy controls and 10 cirrhotic patients, five without and five with ascites were studied after 1 h in a sitting posture and subsequently subjected to 1 h head-out water immersion. Blood was collected for determinations of ET-1, ET-3, ANF, aldosterone, renin activity and noradrenaline. In addition, in 10 patients with compensated cirrhosis the effect of loop diuretics on ET-3, aldosterone and renin was studied. ETs in cirrhosis were significantly (P < 0.01) higher than in controls both before (ET-1, 19.6 +/- 1.3 pgmL-1 vs. 11.8 +/- 0.4 pgmL-1; ET-3, 18.5 +/- 1.4 pgmL-1 vs. 9.5 +/- 0.5 pgmL-1) and after water immersion (ET-1, 18.6 +/- 1.2 pgmL-1 vs. 12.4 +/- 0.3 pgmL-1; ET-3, 18.7 +/- 1.7 pgmL-1 vs. 10.0 +/- 0.5 pgmL-1). In cirrhotic patients, basal and immersion concentrations of ET-1 were significantly correlated to noradrenaline plasma concentrations (r = 0.79, P < 0.05). ET-3 plasma concentrations in cirrhosis were correlated to renin activity (r = 0.65, P < 0.05). Furthermore, ET-3 in cirrhosis was inversely correlated to systolic and mean arterial blood pressure (r = -0.55, P < 0.01 and r = -0.50, P < 0.05; respectively). To investigate the effect of hypovolaemia in compensated cirrhosis, 10 patients without ascites were studied before and after treatment with loop diuretics. In compensated cirrhosis ET-3 was significantly increased 6h after oral diuretic treatment (17.9 +/- 1.0 pgmL-1 vs. 15.5 +/- 0.4 pgmL-1, P < 0.001). The presented data demonstrate relations of endothelins, particularly of ET-3 to neurohumoral systems in patients with cirrhosis of the liver.

Plasma endothelin levels in patients with cirrhosis and their relationships to the severity of cirrhosis and renal function

BACKGROUND/AIMS

Increased plasma endothelin levels have been reported in patients with cirrhosis. However, the relationship between plasma endothelin concentrations and hyperdynamic circulation or renal functions has not been documented.

METHODS

We measured the plasma endothelin-1 and endothelin-3 concentrations using radioimmunoassay in 96 patients with cirrhosis (Pugh's A in 26, Pugh's B in 45 and Pugh's C in 25) and compared these values to 56 age- and sex-matched healthy subjects. Systemic and portal hemodynamic measurements, effective renal plasma flow, creatinine clearance, plasma aldosterone concentration and plasma renin activity were recorded for each patient.

RESULTS

Plasma endothelin-1 and endothelin-3 levels were significantly increased in patients with cirrhosis compared to healthy subjects. Additionally, plasma endothelin-1 and endothelin-3 values were higher in patients with cirrhosis and ascites than in those without ascites. Moreover, plasma endothelin-1 levels increased in relation to the severity of cirrhosis. On the other hand, modest negative correlations were found between endothelin-1 and creatinine clearance or effective renal plasma flow.

CONCLUSIONS

Plasma endothelin-1 and endothelin-3 levels are increased in patients with cirrhosis compared to healthy subjects. The increase in plasma endothelin-1 levels is related at least in part to the severity of cirrhosis. Increased endothelin-1 levels may possibly contribute to renal dysfunction in patients with cirrhosis.

Endothelin-1 and endothelin-3 in cirrhosis: relations to systemic and splanchnic haemodynamics

BACKGROUND/AIMS

Endothelins are isopeptides with potent vasoactive properties, but their implications in the hyperkinetic syndrome in cirrhosis are obscure. Therefore, the aim of the present study was to relate hepatic venous and circulating endothelin-1 and endothelin-3 to systemic and splanchnic haemodynamics.

METHODS

Endothelin-1 and endothelin-3 were measured in samples from a hepatic vein and the femoral artery in 42 patients with cirrhosis, eight hypertensive controls and 10 normotensive controls.

RESULTS

Hepatic venous endothelin-1 was significantly higher in the patients with cirrhosis, mean 21.2 +/- 0.9 pg/ml (SEM) than in the hypertensive controls, 12.4 +/- 2.4 pg/ml, and normotensive controls, 9.6 +/- 1.6 pg/ml (p < 0.00001). Similarly arterial endothelin-1 was significantly higher in the patients with cirrhosis than in the controls (p < 0.00001). Hepatic venous endothelin-1 was significantly correlated with the hepatic venous pressure gradient (r = 0.61, p < 0.00004), serum creatinine (r = 0.35, p < 0.03), diastolic blood pressure (r = -0.31, p < 0.05), central and arterial blood volume (-0.36, p < 0.05), central circulation time (r = -0.41, p < 0.02), and serum sodium (r = -0.56, p < 0.00002) in the patients with cirrhosis. The hepatosplanchnic release of endothelin-1, assessed as the arteriohepatic-venous difference adjusted for hepatic plasma flow, was higher in the group with cirrhosis, 1.5 +/- 0.4 ng/min, than in the normotensive controls, -0.1 +/- 0.2 ng/min (p < 0.01), and was furthermore correlated to the cardiac output in the group with cirrhosis (r = 0.35, p < 0.04). Hepatic venous endothelin-3 was higher in the patients with cirrhosis, 19.0 +/- 1.4 pg/ml (n = 23), as compared with hypertensive controls, 14.2 +/- 1.3 pg/ml, and normotensive controls, 10.0 +/- 1.4 pg/ml (p < 0.002). The same pattern was found in arterial endothelin-3. Hepatic venous endothelin-3 correlated significantly with central and arterial blood volume (r = 0.56, p < 0.02). The hepatosplanchnic release of endothelin-3 was higher in the patients with cirrhosis, 1.0 +/- 0.7 ng/min, than in the normotensive controls, -0.7 +/- 0.4 ng/min (p = 0.05).

CONCLUSIONS

In the presence of cirrhosis, hepatic venous and circulating endothelin-1 and endothelin-3 are elevated with significant relations to systemic and splanchnic haemodynamics, and the hepatosplanchnic release of both peptides is increased. This suggests that the endothelin system is implicated in both systemic and portal haemodynamic abnormalities in cirrhosis, although this study does not allow conclusions on causal relationships.

Increased plasma endothelin in cirrhosis. Relationship with systemic endotoxemia and response to changes in effective blood volume

BACKGROUND/AIMS

Patients with cirrhosis and ascites show high plasma concentrations of endothelin. The aim of the current study was to investigate whether this feature is a compensatory response to effective hypovolemia or a consequence of systemic endotoxemia.

METHODS

Protocols 1 and 2 assess the effect of acute changes in effective blood volume on plasma endothelin, and protocol 3 investigates the relationship between plasma endotoxin and endothelin in patients with cirrhosis and ascites. Protocol 1 included nine healthy subjects and 26 patients with cirrhosis studied during supine rest, upright tilt (which decreases effective blood volume) and cycloergometric exercise (which activates vasoactive systems by a baroreceptor independent mechanism). Protocol 2 included six patients studied before and 1 and 3 h after the intravenous administration of a plasma expander. In protocol 3, the plasma levels of endothelin and endotoxin were measured in 17 non-infected patients with cirrhosis and also in four patients with spontaneous bacterial peritonitis at diagnosis and following resolution of infection.

RESULTS

Plasma endothelin was 3-5 times higher in patients with cirrhosis than in healthy volunteers. In healthy subjects, upright tilt and exercise were associated with a significant activation of the renin-aldosterone and sympathetic nervous systems and an increase in plasma endothelin. In patients with cirrhosis, upright tilt and exercise were associated with a significant increase and plasma volume expansion with a marked suppression of the renin-aldosterone and sympathetic nervous systems. However, in these patients none of these maneuvers affected plasma endothelin levels. In the patients with cirrhosis in protocol 3, there was no correlation between plasma endotoxin and endothelin. Resolution of peritonitis was associated with a marked fall in plasma endotoxin and no changes in plasma endothelin.

CONCLUSIONS

These findings suggest that mechanisms other than effective hypovolemia or systemic endotoxemia are involved in the increased plasma endothelin of cirrhosis with ascites.

Endothelin concentration in plasma of healthy dogs and dogs with congestive heart failure, renal failure, diabetes mellitus, and hyperadrenocorticism

Plasma concentrations of endothelin (ET)-1 and -3 were determined simultaneously in dogs with various pathophysiological conditions, because these peptides may display different pharmacological profiles. The study pays special attention to the characterization of plasma ET immunoreactivity (ET-IR), using high-pressure liquid chromatography (HPLC) analysis with off-line detection by radio-immunoassay (RIA). In most sick dogs evaluated total plasma ET-1-IR concentration did not differ from that of healthy dogs. However, HPLC analysis of their total plasma ET-1-IR revealed distinct ET-IR profiles. Big-ET-1, which is barely detectable in control dogs, does represent the predominant ET in sick dogs. Regardless of the pathophysiological conditions, considerable amounts of high-molecular weight ET-1-IR, most likely aggregated ET-material, was found consistently. With respect to ET-3, we constantly observed moderately increased concentrations, though no major difference of molecular pattern was evident between healthy and sick dogs. The data show a distinct regulation of ET-1 and ET-3 in dogs. Furthermore, specific molecular forms of ET-IR were found to occur in various diseases. The endothelins may therefore prove to be of diagnostic importance in the pathophysiology of vascular diseases.

Noise-induced elevations of plasma endothelin (ET-3)

The endothelins (ETs) are a novel family of peptides which participate in hemodynamic homeostasis. Elevated levels of circulating ETs are evident in several stress related conditions and are associated with a variety of vascular pathophysiologies. The purpose of the current study was to test the possibility that plasma concentrations of endothelin increase following noise exposure using radioimmunoassay (RIA). No difference in plasma endothelin was detected in rats subjected to brief noise exposure (30 min of 100 dB SPL broad-band noise) compared to control animals. Statistically significant elevations in plasma endothelin (ET-3) were measured in animals exposed to prolonged noise exposure (90 min and 72 h of 100 dB SPL broad-band noise). These results suggest that hemodynamic alterations, and potential vascular pathophysiologies accompanying prolonged exposure to noise are mediated by endothelin.