Plasma endothelin-1 levels in stable and unstable angina

Serum Endothelin-1 Correlates with Myocardial Injury and Independently Predicts Adverse Cardiac Events in Non-ST-Elevation Acute Myocardial Infarction

Introduction

Serum endothelin-1 is increasingly released in acute myocardial infarction, by necrotic cardiomyocytes. In non-ST-elevation acute myocardial infarction (Non-STEMI), increased serum endothelin-1 on-admission may have clinical significance during acute hospitalisation events.

Objective

The purpose of this study is to investigate whether increased serum endothelin-1 level predict adverse cardiac events in patients hospitalized with Non-STEMI.

Methods

The design of this research was a prospective cohort study. Consecutive subjects with Non-STEMI undergoing symptom onset ≤24 hour were enrolled and observed during intensive hospitalization. Serum endothelin-1, troponin-I, and hs-C reactive protein were measured from peripheral blood taken on-admission. In-hospital adverse cardiac events were a composite of death, acute heart failure, cardiogenic shock, reinfarction, and resuscitated VT/VF.

Results

We enrolled 66 subjects. The incidence of in-hospital adverse cardiac events is 13.6% (10 out of 66 subjects). Serum endothelin-1 level was significantly higher in subjects with in-hospital adverse cardiac events. Subjects with endothelin-1 level >2.59 pg/mL independently predicted adverse cardiac events in hospitalised Non-STEMI patients (adjusted odds ratio 44.43, 95% confidence interval: 1.44-1372.99, p value 0.03). The serum endothelin-1 level was correlated with serum troponin I level (correlation coefficient of 0.413, p value 0.012).

Conclusion

Increased serum endothelin-1 on-admission correlated with increased troponin-I and independently predicted in-hospital adverse cardiac events in patients with Non-STEMI.

Cardioprotection and improvement in endothelial-dependent vasodilation during late-phase of whole body hypoxic preconditioning in spontaneously hypertensive rats via VEGF and endothelin-1

The present study was designed to investigate the effect of late phase of whole body hypoxic preconditioning on endothelial-dependent vasorelaxation and cardioprotection from ischemia-reperfusion injury in spontaneously hypertensive rats (SHR). Hypoxic preconditioning was performed by subjecting rats to four episodes of alternate exposure to low O₂ (8%) and normal air O₂ of 10 min each. After 24 h, the mesenteric arteries and hearts were isolated to determine the vascular function and cardioprotection from ischemia-reperfusion (I/R) injury on the Langendorff apparatus. There was a significant impairment in acetylcholine-induced relaxation in norepinephrine precontracted arteries (endothelium-dependent function) and increase in I/R-induced myocardial injury in SHR in comparison to Wistar Kyoto rats (WKY). However, hypoxic preconditioning significantly restored endothelium-dependent relaxation in SHR and attenuated I/R injury in both SHR and WKY. Hypoxic preconditioning also led to an increase in the levels of endothelin-1 (not endothelin-2 or -3), vascular endothelial growth factor-A (VEGF-A) and HIF-1α levels. Pretreatment with bevacizumab (anti-VEGF-A) and bosentan (endothelin receptor blocker) significantly attenuated hypoxic preconditioning-induced restoration of endothelium-dependent relaxation and cardioprotection from I/R injury. These interventions also attenuated the levels of VEGF-A and HIF-1α without modulating the endothelin-1 levels. It may be concluded that an increase in the endothelin-1 levels with a subsequent increase in HIF-1α and VEGF expression may possibly contribute in improving endothelium-dependent vasorelaxation and protecting hearts from I/R injury in SHR during late phase of whole body hypoxic preconditioning.

Involvement of Endothelin 1 in Remote Preconditioning-Induced Cardioprotection through connexin 43 and Akt/GSK-3β Signaling Pathway

The present study was aimed to explore the role of endothelins in remote preconditioning (RP)-induced myocardial protection in ischemia-reperfusion (IR) injury. RP stimulus was given by subjecting hind limb to four cycles of ischemia and reperfuion (5 minutes each) using blood pressure cuff in male rats. Following RP, hearts were isolated and subjected to 30 minutes of ischemia and 120 minutes of reperfusion on Langendorff apparatus. The extent of myocardial injury was determined by measuring the levels of LDH-1, CK-MB and cardiac troponin T (cTnT) in coronary effluent; caspase-3 activity and Bcl 2 expression in heart (apoptosis); infarct size by triphenyl tetrazolium chloride and contractility parameters including left ventricular developed pressure, dp/dt_max dp/dt_min and heart rate. RP reduced ischemia reperfusion-induced myocardial injury, increased the levels of endothelin 1 (in blood), Akt-P, GSK-3β-P and P-connexin 43 (in hearts). Pretreatment with ET_A receptor antagonist, BQ 123 (1 and 2 mg/kg), ET_B receptor antagonist, BQ 788 (1 and 3 mg/kg) and dual inhibitor of ET_A and ET_B receptor, bonsentan (25 and 50 mg/kg) abolished these effects of RP. However, the effects of bonsentan were more pronounced in comparison to BQ 123 and BQ 788. It is concluded that RP stimulus may release endothelin 1 in the blood, which may activate myocardial ET_A and ET_B receptors to trigger cardioprotection through connexin 43 and Akt/GSK-3β pathway.

Endothelial immunomediated reactivity in acute cardiac ischaemia: Role of endothelin 1, interleukin 8 and NT-proBNP in patients affected by unstable angina pectoris

The role of endothelium in the progression of atheromasic disease has already been demonstrated. Endothelin-1 (ET-1) is released from endothelial cells during acute and chronic vascular damage and it appears to be the strongest vasoconstrictor agent known.The aim of this study is to investigate the amount of endothelial damage in patients with unstable angina (UA), as defined by serum levels of ET-1, to verify a possible correlation with increased ischaemic damage by evaluation of serum N-terminal pro-brain natriuretic peptide (NT-proBNP) and interleukin 8 (IL-8) levels.Serum levels of ET-1, IL-8 and NT-proBNP obtained from 10 patients affected by low-risk UA were compared to those belonging to eight healthy subjects. In order to compare the laboratory data pertaining to the two populations, a Student's t-test and a Mann-Whitney U test were performed.Levels of ET-1, IL-8 and NT-proBNP in samples of peripheral blood of patients affected by UA were significantly elevated, compared with those of the control group. The linear correlation analysis demonstrated a positive and significant correlation between levels of ET-1 and IL-8, between levels of ET-1 and NT-proBNP, and between levels of IL-8 and NT-proBNP in subjects affected by UA.Early elevated levels of ET-1, IL-8 and NT-proBNP in patients with UA show a coexistence between ischaemic insults and endothelial damages. A positive and significant linear correlation between levels of ET-1 and IL-8, between levels of ET-1 and NT-proBNP, and between levels of IL-8 and NT-proBNP confirms that an increased ischaemic insult is correlated to inflammation signs and endothelium damage signs.In patients with UA, ischaemia is always associated with a systemic immuno-mediated activity induced by acute endothelial damage. We suggest early administration of ET-1-selective receptor blockers and anti-inflammatory drugs.

Endothelin receptor antagonist BQ-123 ameliorates myocardial ischemic-reperfusion injury in rats: a hemodynamic, biochemical, histopathological and electron microscopic evidence

We investigated the effect of BQ-123, a selective endothelin-A (ET(A)) receptor antagonist in ischemia-reperfusion (IR) induced myocardial infarction (MI) with and without endothelin-1 (ET-1) challenge. MI was produced in rats by occlusion of left anterior descending coronary artery for 40 min and reperfusion for 120 min. ET-1 was administered immediately prior to coronary occlusion whereas vehicle or BQ-123 was administered 20 min after the occlusion. IR control group exhibited marked hemodynamic changes along with significant impairment of left ventricular functions. In addition, oxidative stress was increased, as evidenced by marked reduction in the activities of antioxidants and cardiac injury markers in myocardium. Furthermore, light microscopic and ultrastructural changes revealed myocardial necrosis, edema and inflammation. Prior administration of ET-1 acts synergistically with IR injury and further aggravates the impairment of ventricular functions, increased percent infarct area and decreased antioxidant levels. However, treatment with BQ-123 (1 mg/kg, IV) with or without ET-1 caused significant improvement in cardiac functions, percent infarct area, decreased malonaldehyde level, restored myocardial enzymes activities and maintained the redox status of the myocardium as compared to IR control group. Further, histopathological and ultrastructural studies reconfirmed the protective action of BQ-123. The results of present study suggest that ET-1 acting via ET(A) receptor may exaggerate myocardial damage produced by IR injury and selective blockade of ET(A) receptor by BQ-123 might offer potential cardioprotective action.

Endogenous endothelin stimulates cardiac sympathetic afferents during ischaemia

Myocardial ischaemia activates cardiac sympathetic afferents leading to chest pain and reflex cardiovascular responses. Previous studies have shown that a brief period of myocardial ischaemia increases endothelin in cardiac venous plasma draining ischaemic myocardium and that exogenous endothelin excites cutaneous group III and IV sensory nerve fibres. The present study tested the hypothesis that endogenous endothelin stimulates cardiac afferents during ischaemia through direct activation of endothelin A receptors (ET(A)Rs). Nerve activity of single unit cardiac sympathetic afferents was recorded from the left sympathetic chain or rami communicates (T(2)-T(5)) in anaesthetized cats. Single fields of 38 afferents (CV = 0.25-3.86 m s(-1)) were identified in the left or right ventricle with a stimulating electrode. Five minutes of myocardial ischaemia stimulated all 38 cardiac afferents (8 Adelta, 30 C-fibres) and the responses of these 38 afferents to chemical stimuli were further studied in the following protocols. In the first protocol, injection of endothelin 1 (ET-1, 1, 2 and 4 microg) into the left atrium (LA) stimulated seven ischaemically sensitive cardiac afferents in a dose-dependent manner. Second, BQ-123, a selective ET(A)R antagonist, abolished the responses of nine afferents to 2 microg of ET-1 injected into the left atrium and attenuated the ischaemia-related increase in activity of eight other afferents by 51%. In contrast, blockade of ET(B) receptors caused inconsistent responses to exogenous ET-1 as well as to ischaemia. Furthermore, in the absence of ET(A)R blockade, cardiac afferents responded consistently to repeated administration of ET-1 (n = 7) and to recurrent myocardial ischaemia (n = 7). Finally, using an immunocytochemical staining approach, we observed that ET(A) receptors were expressed in cardiac sensory neurons in thoracic dorsal root ganglia. Taken together, these data indicate that endogenous endothelin contributes to activation of cardiac afferents during myocardial ischaemia through direct stimulation of ET(A) receptors likely to be located in the cardiac sensory nervous system.

Association of endothelin-1 with transient myocardial ischemia in patients with unstable angina pectoris

In this study we assessed whether serum endothelin-1 levels were associated with indexes of disease severity in unstable angina, including troponin I, C-reactive protein, and transient myocardial ischemia. Endothelin-1 levels were higher in patients who had transient myocardial ischemia and in those who had 3-vessel disease on angiography but were not significantly correlated with levels of C-reactive protein and troponin I.

Clinical Significance of Acute-Phase Endothelin-1 in Acute Myocardial Infarction Patients Treated With Direct Coronary Angioplasty

BACKGROUND

The aim of the present study was to investigate the relationship between plasma concentrations of endothelin (ET)-1 and clinical outcome (including mortality) and left ventricular (LV) systolic function in acute myocardial infarction (AMI).

METHODS AND RESULTS

The study group comprised 110 consecutive first-AMI patients who were successfully reperfused by primary coronary intervention. Plasma ET-1 concentrations were evaluated 24 h from onset and the patients were divided into 2 groups according to the median value, either a high group (H group: > or = 2.90 pg/ml plasma ET-1; n = 55) or low group (L group: < 2.90 pg/ml plasma ET-1; n = 55). Major complications and LV systolic function were monitored in the 2 groups. Both highly sensitive C-reactive protein (hs-CRP) and brain natriuretic peptide (BNP) showed a significant positive correlation with ET-1 (BNP: r = 048, p < 0.0001, hs-CRP: r = 0.43, p < 0.001). Chronic stage left ventricular ejection fraction (LVEF) and left ventricular end-diastolic volume index (LVEDVI) were significantly poorer in the H group (LVEF: 51+/-15% vs 60+/-13%, p = 0.003, LVEDVI: 74+/-19 ml/m2 vs 66+/-14 ml/m2, p < 0.05). There were significantly more major complications in the H group than in the L group (cardiogenic shock: 18% vs 5%, p = 0.04; cardiac death: 13% vs 0%, p < 0.01).

CONCLUSIONS

In the setting of AMI, plasma ET-1 concentrations may be closely related to LV systolic dysfunction and poor patient outcome, including mortality.

Differentiated and dose-related cardiovascular effects of a dual endothelin receptor antagonist in endotoxin shock

OBJECTIVE

To evaluate the effects of endothelin receptor antagonism on cardiac performance in endotoxin shock.

DESIGN

Prospective, experimental study.

SETTING

A university-affiliated research institution.

SUBJECTS

Domestic anesthetized landrace pigs.

INTERVENTIONS

Thirty-seven pigs were anesthetized and subjected to echocardiography, coronary sinus catheterization, and monitoring of central and regional hemodynamics in order to assess cardiac performance. All animals received endotoxin for 5 hrs. Twenty pigs served as endotoxin controls. Tezosentan, a dual endothelin-A and -B receptor antagonist, was administered during established endotoxemic shock. Seven pigs received an infusion of tezosentan of 1 mg x kg(-1) x hr(-1) (tezo1), and an additional ten pigs received a higher dose of 10 mg x kg(-1) x hr(-1) (tezo10).

MEASUREMENTS AND MAIN RESULTS

Endotoxemia evoked a state of shock with pulmonary hypertension and metabolic acidosis. A decrease in stroke volume and coronary perfusion pressure as well as an increase in troponin I was also noted. Tezosentan administration resulted in a significant increase in cardiac index, stroke volume index, left ventricular stroke work index, and left ventricular end-diastolic area index. Decreases in systemic and pulmonary vascular resistance indexes were also evident after intervention. This was achieved without changes in heart rate or systemic arterial or pulmonary artery occlusion pressures in tezo, animals compared with controls. In addition, metabolic variables were improved by tezosentan. These effects were sustained only in the tezo, group. In the higher dosage, tezosentan resulted in a deterioration of cardiac performance and 50% mortality rate. The endotoxin-induced increase in troponin I was attenuated in the tezo, group compared with controls.

CONCLUSIONS

In this porcine model of volume-resuscitated, endotoxemic shock, endothelin-receptor blockade with tezosentan improved cardiac performance. However, the effect was not sustained with higher doses of tezosentan, possibly due to reduced coronary perfusion pressure. These findings show differentiated, dose-dependent effects by dual endothelin receptor blockade on endotoxin-induced cardiovascular dysfunction.

Circadian variation in myocardial ischemia: the possible mechanisms involving in this phenomenon

Circadian rhythms have long been recognized to occur in many biologic phenomena, including secretion of hormones as well as autonomic nervous system. There is increasing evidence that circadian rhythms have been also found in cardiovascular events, for example, myocardial infarction, sudden cardiac death as well as stroke have shown a circadian pattern of the distribution. Transient myocardial ischemia, detected by ambulatory ST segment monitoring, is also unevenly distributed during the day. The pathophysiology and the mechanism underlying these variations are the focus of much investigation, while it is not full understood up to date. Heart rate, blood pressure, neural and humoral vasoactive factors such as plasma norepinephrine levels and renin activity, and probably also contractility are increased in the morning hours, indicating that increase in myocardial oxygen demand contribute importantly to the increased prevalence of ischemia in the morning. Our recent study found that circadian rhythm of ischemic threshold detected by repetitive exercise treadmill tests in patients with chronic coronary artery disease is also apparently associated with levels of plasma ET-1. This information should enable better understanding as well as treatment on patients on circadian variation of cardiovascular events.

Circadian variation in ischemic threshold in patients with stable angina: relation to plasma endothelin-1

To investigate circadian variation in ischemic threshold in chronic coronary heart disease (CHD) and its relation to plasma endothelin-1 (ET-1), 21 patients with stable angina underwent treadmill exercise tests twice within a day, performed at 8-9 AM for the first test and at 3-4 PM for the second one. Ischemic threshold was defined as the heart rate at the onset of 1 mm ST segment depression during exercise tests. Blood samples were taken at 5 minutes before each exercise test, and plasma ET-1 was measured for determining the possible relation to ischemic threshold in patients with CHD. The results showed that the heart rate-ischemic threshold in individual patients varied by 10 +/- 1% (range, 2-15%) in the morning and 9 +/- 1% (range, 2-14%) in the afternoon, while there was a mean (11.2%) reduction in the ischemic threshold between 2 time points, with the ischemic threshold being significantly lower in the morning compared with that in the afternoon (115 +/- 22 bpm vs 128 +/- 31 bpm p<0.04). ET-1 values were 6.20 +/- 2.44 ng/L in the morning hours and 4.02 +/- 1.61 ng/L in the afternoon hours, with a statistical significant difference (p<0.01). In conclusion, the present study indicated that circadian variation of plasma levels of ET-1 was likely to be one of the most likely mechanisms involved in reduction in the ischemic threshold in the morning hours.

Short-term endothelin receptor blockade with tezosentan has both immediate and long-term beneficial effects in rats with myocardial infarction

OBJECTIVES

We investigated the effects of short-term tezosentan treatment on cardiac function, pulmonary edema and long-term evolution of heart failure (HF) in a rat model of myocardial infarction (MI).

BACKGROUND

Endothelin (ET) may play a major role in the progression from MI to HF. Tezosentan is a new dual ET(A)/ET(B) receptor antagonist.

METHODS

Rats were subjected to coronary artery ligation and were treated with either vehicle or tezosentan (10 mg/kg IV bolus) at 1 h and 24 h after MI. Cardiac hemodynamics and lung weight were measured at 48 h after MI. Survival was assessed over a five-month period.

RESULTS

At 48 h after ligation, vehicle-treated rats developed HF, as evidenced by a marked increase in left ventricular end-diastolic pressure (LVEDP), reduction in dP/dt(max) and mean arterial pressure (MAP), and development of pulmonary edema. Tezosentan treatment attenuated the increase in LVEDP and in lung weight and slightly reduced MAP without affecting dP/dt(max). Infarct size was not modified by tezosentan. Despite the fact that treatment with tezosentan was stopped after 24 h, the initial tezosentan administration significantly reduced cardiac hypertrophy (22%) and decreased mortality by 51% at five months (50% survival vs. 19% survival in vehicle-treated rats, p < 0.001).

CONCLUSIONS

Tezosentan administered during the first day after MI in rats, in addition to improving acutely hemodynamic conditions, markedly increases long-term survival. This increase is associated with a decrease of pulmonary edema and prevention of cardiac hypertrophy. Tezosentan could be a safe and useful therapeutic agent in the prevention and treatment of ischemic HF.

Evaluation of plasma endothelin-1 levels in patients with cerebral infarction

Endothelin-1 (ET-1) is a vasoconstrictor peptide derived from endothelium. Many authors have shown that ischemic stroke is associated with elevated plasma ET-1 levels. Also, the present findings related to plasma ET-1 levels with clinical status, size of the infarction, location of the infarction, and prognosis of the cerebral infarction were contradictory. In this study, plasma ET-1 levels in 30 patients with cerebral infarction within 72 hours after the onset of focal neurologic deficit and at their seventh day postinfarction were measured by a microplate enzyme immunoassay. Thirty sex- and age-matched healthy subjects were accepted as a control group. The mean plasma ET-1 concentrations in patients on admission, in patients at day 7, and in control subjects were 1.93 +/- 1.79, 1.03 +/- 1.02, and 0.65 +/- 0.32 fmol/mL, respectively. The mean plasma ET-1 level of patients on admission was found to be significantly higher than in patients at day 7 and in control subjects (p < 0.05). No significant difference in ET-1 levels was observed between the patients at day 7 and control subjects. Furthermore, there was no correlation between plasma ET-1 concentration and size of infarction, location of infarction, degree of clinical neurologic deficit, or prognosis of cerebral infarction. It was concluded that plasma ET-1 levels shortly after ischemic stroke were increased, which may be associated with the acute-phase reaction of cerebral infarction and may have deleterious effects on development of neuronal injury.

[Endothelial dysfunction in patients with acute coronary syndrome]

Increased vasoconstriction, activation of platelet vessel wall interaction and invasion of monocytes into the subintima as well as vascular smooth muscle cell proliferation play a fundamental role in the pathogenesis of coronary artery disease. Acute coronary syndromes such as myocardial infarction and unstable angina pectoris are characterized by plaque rupture or erosion, activation of platelets and the coagulation system and vasoconstriction. Endothelial dysfunction may be one of the underlying mechanisms linking coronary artery disease and acute coronary syndromes. Both of these are often temporarily limited. Therefore, "non-invasive examination" of endothelial function by venous occlusion plethysmography or high resolution ultrasound might be useful for monitoring high-risk patients.

Experimental optic cup enlargement caused by endothelin-1-induced chronic optic nerve head ischemia

PURPOSE

Vascular insufficiency of the optic nerve head may contribute to glaucomatous optic neuropathy, especially in normal-tension glaucoma. We investigated the effect of chronic optic nerve head ischemia, created by repeated intravitreal injection of endothelin-1 (ET-1), on the morphology and function of the optic nerve.

METHODS

In pigmented rabbits, we injected ET-1 (10(-6) M, 10 microL) into the posterior vitreous of one eye twice a week for 4 weeks (N = 7). The vehicle for ET-1 was injected into the contralateral eye as a control (N = 7). The subsequent observation period was set at 8 weeks. The microcirculation of the optic nerve head was noninvasively monitored with a laser speckle circulation analyzer. To evaluate the changes of visual function, visual-evoked potentials were recorded. Morphologic changes of the optic nerve head were analyzed with stereography, and the ratio of cup area (CA) to disk area (DA) was measured by calculating the number of pixels in each area with a microcomputer.

RESULTS

Capillary blood flow in the optic nerve head was continuously below 80% of the baseline throughout the study. The visual-evoked potential latency was significantly delayed in ET-1-treated eyes. The CA/DA ratio was significantly increased relative to baseline in the ET-1 treated eyes. Histologic examination showed axonal loss and demyelination affecting the prelaminar portion of the optic nerve. The intraocular pressure was not significantly different from the control value.

CONCLUSION

Optic nerve head ischemia could contribute to the enlargement and excavation of the disk cup independent of the intraocular pressure level.

Plasma levels of cyclic GMP and endothelin in postmenopausal women with unstable coronary artery disease

Many women with typical anginal chest pain have normal coronary angiograms, which may be due to altered endothelial function. We evaluated the endothelial markers cyclic GMP (cGMP) and immunoreactive endothelin (ir-ET) regarding presence of coronary atherosclerosis in women with clinical signs of unstable coronary artery disease (CAD). Plasma levels of cGMP and ir-ET were determined in 118 patients and 84 controls. Ischaemia was evaluated at an exercise test. Of the patients 20% had normal vessels, 14% insignificant CAD and 66%, significant stenosis at coronary angiography. Mean (95% CI) concentration of cGMP (nmol/l) was higher in patients than in controls (5.05 (4.53; 5.58) vs. 3.79 (3.34; 4.23)). Separating patients according to daily intake of nitroglycerin, only patients with this medication had significantly higher cGMP level (5.73 (4.88; 6.58)), whereas the difference between those without (4.35 (3.76; 4.94)) and controls disappeared. Patients with ischaemia at exercise test had higher cGMP level than those without (6.01 (5.13; 6.88) vs. 4.30 (3.66; 4.94)), even after adjusting for nitroglycerin treatment. ir-ET (pmol/l) was lower in patients with normal vessels than patients with coronary atherosclerosis (0.83 (0.78; 0.88) vs. 0.98 (0.92; 1.04)) and than the control group (0.91 (0.87; 0.94)). The difference between the control group and patients with atherosclerosis was also significant. Patients with unstable CAD and long-term nitroglycerin treatment have increased cGMP level. Patients with exercise-induced ischaemia have higher cGMP level than those without, irrespective of nitroglycerin treatment, which may reflect a general compensatory mechanism. Patients with normal vessels have low level of ir-ET, indicating different mechanisms for ischaemia/angina in these patients compared with patients with atherosclerosis.

Cholesterol reduction rapidly improves endothelial function after acute coronary syndromes. The RECIFE (reduction of cholesterol in ischemia and function of the endothelium) trial

BACKGROUND

Cholesterol lowering reduces coronary events. One mechanism could be improvement of endothelial function. In line with this hypothesis, this study investigates whether cholesterol reduction can result in rapid improvement of endothelial function after acute coronary syndromes.

METHODS AND RESULTS

Patients with acute myocardial infarction or unstable angina and total cholesterol levels at admission >/=5.2 mmol/L or LDL >/=3.4 mmol/L were randomized to placebo (n=30) or pravastatin 40 mg daily (n=30) for 6 weeks. Brachial ultrasound was used to measure endothelium-dependent flow-mediated dilatation (FMD) and response to endothelium-independent nitroglycerin. Changes in the levels of markers of platelet activation, coagulation factors, and plasma endothelin levels were also assessed. Total and LDL cholesterol levels were similar at admission and before randomization in both groups. With pravastatin, but not with placebo, they decreased by 23% (P<0.05) and 33% (P<0.01), respectively. FMD was unchanged with placebo, 5.43+/-0.74% (mean+/-SEM) to 5.84+/-0.81%, but increased with pravastatin, 4.93+/-0.81% to 7.0+/-0.79% (P=0.02), representing a 42% relative increase. Responses to nitroglycerin were similar during the time course of the study in the 2 groups. Markers of platelet activity, coagulation factors, and endothelin levels were not affected by pravastatin.

CONCLUSIONS

Cholesterol reduction with pravastatin initiated early after acute coronary syndromes rapidly improves endothelial function after 6 weeks of therapy.

Hemodynamic effects of endothelin-1 and big endothelin-1 in chronic hemodialysis patients

Increased plasma concentrations of endothelin-1 (ET-1) and big endothelin-1 (big ET-1) have been reported in patients with end-stage renal failure (ESRD). In the present study, which included hemodialysis (HD) patients with (n = 21) and without (n = 32) ischemic heart disease, the putative association between plasma levels of ET-1 and big ET-1 and ischemic heart disease and the influence of the dialysis procedure on ET concentrations was investigated. This study also examined in an additional five HD patients without cardiac disease whether intravenously infused ET-1 and big ET-1 (0.2, 1, and 4 pmol/kg per min, each dose for 20 min) preserve their vasoactive potency and whether exogenous big ET-1, which in healthy humans is converted in the kidney, is still converted to ET-1 in ESRD. HD patients with ischemic heart disease demonstrated higher plasma levels of ET-1 and big ET-1 than HD patients without this disorder, and HD reduced plasma ET-1 and big ET-1 concentrations. In HD patients, the big ET-1 infusion, resulting in a 1.5-fold increase in plasma ET-1, caused a more marked and prolonged rise in mean arterial BP than ET-1 (20% versus 13%, P = 0.0001) and a slightly smaller but more prolonged decrease in estimated splanchnic blood flow than ET-1 (37% versus 44%, P = 0.02). Furthermore, big ET-1 lowered heart rate by 9% (P = 0.01) but ET-1 did not. Plasma half-lives of ET-1 and big ET-1 were longer in HD patients than in healthy humans. Thus, ET-1 and big ET-1 preserve their vasoactive potency, and circulating big ET-1 is still converted to active ET-1 in ESRD. Consequently, the increased plasma levels of ET-1 and big ET-1 noted in HD patients, especially in patients with ischemic heart disease, might play a role in the development of uremic cardiovascular complications.

Inotropic effects of endothelin-1: interaction with molsidomine and with BQ 610

-In vivo studies could not detect a positive inotropy of endothelin (ET)-1 as described in in vitro experiments. ET-induced direct positive inotropy, which seems to be mediated by ETB receptors, may be antagonized in vivo by an indirect cardiodepressive effect owing to an ET-induced coronary vasoconstriction via ETA receptors. This study compares the effects of a dose of 1 nmol/kg ET-1 alone on myocardial contractility and myocardial energy metabolism with the effects of 1 nmol/kg ET-1 after pretreatment with 5 mg/kg molsidomine or with 100 microg/kg of the ETA receptor antagonist BQ 610. We investigated the effects of ET-1 versus saline controls in open-chest rats. In addition to measurements in the intact circulation, myocardial function was examined by isovolumic registrations independent of peripheral vascular effects. We also studied the effect of ET-1 on myocardial high-energy phosphates. Pretreatment with molsidomine and BQ 610 attenuated the ET-induced reduction of cardiac output (ET-1: -62%; molsidomine+ET-1: -47%; BQ 610+ET-1: -27% different from controls). After a transient initial vasodilation, ET-1 raised total peripheral resistance (ET-1: +190%; molsidomine+ET-1: +171%; BQ 610+ET-1: +89%). BQ 610 was more effective in preventing ET-induced vasoconstriction. The increase of isovolumic peak first derivative of left ventricular pressure (ET-1: -2%; molsidomine+ET-1: +16%; BQ 610+ET-1: +19%) after pretreatment with molsidomine or BQ 610 indicates that these drugs unmask the positive inotropy of ET-1. ET-induced myocardial ischemia was abolished by molsidomine and BQ 610. Pretreatment with molsidomine or blockade of ETA receptors by BQ 610 can unmask the positive inotropy of ET-1 by preventing ET-induced myocardial ischemia. The positive inotropic effect of ET-1 seems to be mediated by ETB receptors.

Cardiac release and kinetics of endothelin after uncomplicated percutaneous transluminal coronary angioplasty

This study was designed to assess the release kinetics of endothelin after percutaneous transluminal coronary angioplasty (PTCA) and to prove the coronary endothelium as the source of the endothelin release. Twenty-seven patients with single-vessel coronary artery disease underwent PTCA. Endothelin, troponin T, myoglobin, and creatine phosphokinase paired blood samples were withdrawn from the coronary sinus and a peripheral vein before the balloon maneuver and at 1, 5, 10, 30, 45 minute(s), and at 1, 2, 3, 6, 12, and 24 hour(s) after the last balloon maneuver. Myocardial ischemia was monitored by means of cardiac lactate metabolism and 12-lead electrocardiogram. Thirteen patients who underwent a diagnostic cardiac catheterization served as a control group. In the left coronary artery, PTCA (n = 19) endothelin concentrations increased from 4.1 pg/ml as a common mean baseline level before intervention to 13.9 +/- 2.6 pg/ml (mean +/- SD) in the coronary sinus and 7.9 +/- 2.2 pg/ml (mean +/- SD) in the peripheral vein at 1 minute after the intervention (p <0.001). The levels remained elevated for 3 hours with higher coronary sinus than peripheral venous concentrations due to persistent cardiac endothelin release. PTCA of the right coronary artery (n = 8) also led to an instantaneous endothelin increase from a mean concentration of 4.4 before intervention to 8.3 pg/ml after intervention with identical coronary sinus and peripheral venous levels (p <0.001). Endothelin levels gradually decreased to normal within 6 hours. No patient developed a measurable myocardial ischemia or a myocardial infarction. In the control group all parameters remained unchanged. Uncomplicated PTCA was followed by a significant cardiac endothelin release that seems to indicate endothelial injury and not myocardial ischemia.

Hemodynamic and inotropic effects of the endothelin A antagonist BQ-610 in vivo

The positive inotropy of endothelin-1 (ET-1) described by in vitro studies is not detectable in vivo because this effect is antagonized by cardiodepressive effects due to ET-induced vasoconstriction with subsequent myocardial ischemia. This vasoconstriction is mainly mediated by ETA receptors. In a previous in vivo study with a selective ETB receptor agonist, we showed that ETB receptors play an important role in the ET-induced positive inotropy. The present in vivo study examined whether selective ETA receptor blockade can unmask the ETB receptor-mediated positive inotropy of endogenous ET-1 by preventing its cardiodepressive effects via ETA receptors. In an open-chest rat model, we compared the acute hemodynamic and inotropic effects of the highly selective ETA receptor antagonist BQ-610 (100 micrograms/kg) with NaCl controls during and after a 7-min infusion. In addition to measurements in the intact circulation, the effects on myocardial contractility were studied by isovolumic registrations (peak LVSP, peak dP/dtmax), which are independent of peripheral vascular effects. Acute blockade of the ETA receptors by BQ-610 had no effect on blood pressure and heart rate. BQ-610 caused vasodilatation (total peripheral resistance -7.5% vs. control at the end of infusion; p < 0.01) with a consecutive increase in stroke volume (+15.3%; p < 0.01), cardiac output (+15.4%; p < 0.001), and ejection fraction (+10.4%; p < 0.01). The isovolumic measurements indicated a significant positive inotropic effect of BQ-610 (peak LVSP + 4.2%, p < 0.01; peak dP/dtmax + 5.5%, p < 0.01). Therefore, selective ETA receptor blockade by BQ-610 improves the hemodynamics in the intact circulation by causing a reduction in afterload and an increase in myocardial contractility. The positive inotropic effect of BQ-610 may be mediated by the positive inotropy of endogenous ET-1 via ETB receptors after selective ETA receptor blockade.

Plasma endothelin-1 levels in patients with angina pectoris and normal coronary angiograms

BACKGROUND

Some patients with typical angina and electrocardiographic evidence of ischemia have normal coronary angiograms. These patients have a reduced coronary flow reserve and abnormal endothelium-dependent vasodilator responses; this syndrome is known as microvascular angina. Among endothelium-derived peptides, endothelin-1 (ET-1) is a potent vasoconstrictor and an important modulator of microvascular function.

METHODS

Plasma ET-1 was measured in 13 patients with typical angina, instrumental evidence of ischemia, and normal arteriograms and in 20 normal control subjects.

RESULTS

Mean concentration of ET-1 was 2.89+/-1.24 pmol/L in patients with angina and normal angiograms and 1.99+/-0.81 pmol/L in normal control subjects (p < 0.02). Plasma levels of ET-1 values were significantly higher in patients with angina, positive exercise test results for ischemia, and normal coronary arteriograms compared with the group of patients with no clinical or instrumental evidence of ischemia.

CONCLUSIONS

This is consistent with the hypothesis that in patients with microvascular angina, an endothelial dysfunction in the coronary vascular area caused by impaired endothelium-derived ET-1 could play an active role in the disease process.

Cardiac release and kinetics of endothelin after severe short-lasting myocardial ischemia

OBJECTIVES

The aim of this study was to investigate the release kinetics of endothelin after induced short-lasting myocardial ischemia.

BACKGROUND

Endothelin is an endothelium-derived vasoactive peptide. Unequivocal proof of its cardiac release in ischemic syndromes has not yet been demonstrated.

METHODS

A coronary sinus study with atrial pacing was performed in 23 patients with coronary artery disease. Endothelin (ET), cardiac troponin-T (TnT), myoglobin (Mb) and creatine kinase (CK) samples were withdrawn from the coronary sinus and a peripheral vein before and 1, 5, 10, 30 and 45 min and 1, 2, 3 and 6 h after pacing. The appearance of angina pectoris, abnormal cardiac lactate metabolism and ST segment depression were further criteria for myocardial ischemia.

RESULTS

In the study group, pacing stress induced severe ischemia (mean duration +/- SD 6.1 +/- 1.2 min), with a maximum of 0.34 +/- 0.12-mV ST segment depression in 21 of 23 patients and angina pectoris in 22 of 23. The maximal cardiac lactate production was 42.8 +/- 17.3% (p < 0.03). TnT and CK levels in the total group were normal; in 14 of 23 patients a transient elevation of Mb with a maximum after 3 h was detected (86.4 +/- 27.1 micrograms/liter, p < 0.03). The ET concentrations increased significantly (p < 0.001) in the coronary sinus (from 4.6 +/- 0.8 [baseline] to 12.9 +/- 2.7 pg/ml at 1 min after cessation of pacing) and the peripheral vein, respectively (from 4.7 +/- 0.7 [baseline] to 8.3 +/- 2.1 pg/ml at 1 min). ET further remained elevated for 1 h with persisting higher coronary sinus than peripheral venous concentrations, indicating cardiac ET release. In a control group of 18 patients without heart disease, all variables were unchanged.

CONCLUSIONS

Short-lasting severe myocardial ischemia was associated with significant ET release of cardiac origin that lasted up to 1 h.

Evaluation of chest pain in the emergency department

The evaluation of chest pain in the emergency setting should be systematic, risk based, and goal driven. An effective program must be able to evaluate all patients with equal thoroughness under the assumption that any patient with chest pain could potentially be having an MI. The initial evaluation is based on the history, a focused physical examination, and the ECG. This information is sufficient to categorize patients into groups at high, moderate, and low risk. Table 14 is a template for a comprehensive chest-pain evaluation program. Patients at high risk need rapid initiation of appropriate therapy: thrombolytics or primary angioplasty for the patients with MIs or aspirin/heparin for the patients with unstable angina. Patients at moderate risk need to have an acute coronary syndrome ruled in or out expediently and additional comorbidities addressed before discharge. Patients at low risk also need to be evaluated, and once the likelihood of an unstable acute coronary syndrome is eliminated, they can be discharged with further evaluation performed as outpatients. Subsequent evaluation should attempt to assign a definitive diagnosis while also addressing issues specific to risk reduction, such as cholesterol lowering and smoking cessation. It is well documented that 4% to 5% of patients with MIs are inadvertently missed during the initial evaluation. This number is surprisingly consistent among many studies using various protocols and suggests that an initial evaluation limited to the history, physical examination, and ECG will fail to identify the small number of these patients who otherwise appear at low risk. The solution is to improve the sensitivity of the evaluation process to identify these patients. It appears that more than simple observation is required, and at the present time, no simple laboratory test can meet this need. However, success has been reported with a number of strategies including emergency imaging with either radionuclides such as sestamibi or echocardiography. Early provocative testing, either stress or pharmaceutic, may also be effective. The added value of these tests is only in their use as part of a systematic protocol for the evaluation of all patients with acute chest pain. The initial evaluation of the patient with chest pain should always consider cardiac ischemia as the cause, even in those with more atypical symptoms in whom a cardiac origin is considered less likely. The explicit goals for the evaluation of acute chest pain should be to reduce the time to treat MIs and to reduce the inadvertent discharge of patients with occult acute coronary syndromes. All physicians should become familiar with appropriate risk stratification of patients with acute chest pain. Systematic strategies must be in place to assure rapid and consistent identification of all patients and the expedient initiation of treatment for those patients with acute coronary syndromes. These strategies should include additional methods of identifying acute coronary syndromes in patients initially appearing as at moderate or low risk to assure that no unstable patients are discharged. All patients should be followed up closely until the cardiovascular evaluation is completed and, when possible, a definitive diagnosis is determined. Finally, this must be done efficiently, cost-effectively, and in a manner that will result in an overall improvement in patient care.

Plasma endothelin-1 levels in adult patients undergoing coronary revascularization

Cardiopulmonary bypass is thought to injure all endothelial cells, mainly by cell-to-cell interaction with activated granulocytes which, augmented by endothelin-1 (ET-1), enhance the generation of superoxide radicals. These radicals on the other hand, may sustain and prolong endothelial injury. In the present study, by means of a magnetic separation radioimmunoassay procedure, ET-1 levels were measured in 10 adult patients undergoing coronary artery bypass surgery, in 10 perioperative phases, in order to reconfirm and further elucidate the effect of cardiopulmonary bypass on endothelial secretion of ET-1. ET-1 levels before cardiopulmonary bypass showed a definite rising trend, especially after median sternotomy. After induction of cardiopulmonary bypass, ET-1 levels increased significantly compared with preoperative values (P < 0.01). ET-1 levels in stable angina patients during and after aortic cross-clamping were strongly and positively correlated with preoperative mean pulmonary artery pressure (r = 0.79, n = 7, P < 0.05 and r = 0.92, n = 7, P = 0.05) respectively. After the first hour in the intensive care unit, ET-1 levels in three patients with unstable angina were considerably higher than in those with stable angina, a fact that deserves further consideration and study.

Short-term hemodynamic effects of endothelin receptor blockade in dogs with chronic heart failure

BACKGROUND

Plasma endothelin levels are increased in heart failure and may contribute to the increased peripheral vasoconstriction that characterizes this disease state. In the present study, we examined the effects of intravenous bosentan, a nonpeptide, competitive endothelin-1 receptor antagonist, on hemodynamics in dogs with chronic heart failure.

METHODS AND RESULTS

Chronic heart failure was produced in 11 dogs by multiple sequential intracoronary microembolization. At the time of study, left ventricular (LV) ejection fraction was 25 +/- 2%. Hemodynamic and echocardiographic measurements were made at baseline and at 15, 30, and 60 minutes after a bolus injection of bosentan (10 mg/kg). Bosentan had no significant effect on heart rate or mean aortic blood pressure. At 60 minutes, bosentan reduced LV end-diastolic pressure (17 +/- 2 versus 11 +/- 2 mm Hg; P < .05) and systemic vascular resistance (3891 +/- 379 versus 3071 +/- 346 dyne .s. cm-5; P < .05) compared with baseline and increased cardiac output (2.63 +/- 0.29 versus 3.33 +/- 0.46 L/min; P < .05), peak rate of change of LV pressure during isovolumic contraction and relaxation (1751 +/- 92 versus 2197 +/- 170 mm Hg/s; P < .05), and LV fractional shortening determined by echocardiography (30 +/- 2% versus 36 +/- 2%; P < .05).

CONCLUSIONS

Short-term intravenous bosentan reduced systemic vascular resistance and improved overall LV performance in dogs with chronic heart failure. These results suggest that endothelin-1 receptor antagonists may be useful therapeutic agents in the treatment of heart failure.

Plasma immunoreactive endothelin concentration correlates with severity of coronary artery disease in patients with stable angina pectoris and normal ventricular function

OBJECTIVES

The present study tested the hypothesis that plasma immunoreactive endothelin concentration correlates with the severity and extent of coronary atherosclerosis.

BACKGROUND

Plasma endothelin-1 concentration is increased in patients with unstable coronary syndromes and advanced atherosclerosis. This finding, together with other clinicopathologic observations, suggests that endothelins may participate in the atherogenic process. However, the relation between plasma immunoreactive endothelin and coronary artery disease in patients with stable angina pectoris remains controversial.

METHODS

Ninety consecutive patients undergoing coronary angiography for the investigation of exertional chest pain and 49 normal control subjects were prospectively studied. Eleven patients had normal coronary angiographic findings (group I), 65 had coronary artery stenoses (group II), and 14 had coronary artery disease plus symptoms indicating atheroma in other vascular territories (group III). Computerized angiography was used to determine the extent, severity and morphology of coronary stenoses. Plasma immunoreactive endothelin was measured by radioimmunoassay.

RESULTS

Mean (+/- SD) plasma endothelin concentration (pg/ml) was significantly higher in patients than in control subjects (7.29 +/- 4.07 vs. 3.48 +/- 1.29, p < 0.0001). Endothelin levels were higher in patients of group III than in those of groups II and I (9.43 +/- 5.48, 7.20 +/- 3.72 and 4.94 +/- 2.89, respectively, p = 0.02). In patients of group II, plasma endothelin correlated with the maximal degree of stenosis in each patient (r = 0.25, p = 0.04) and with the number of stenoses with > or = 70% diameter narrowing (r = 0.36, p = 0.002). The highest plasma endothelin levels were found in patients with total occlusions (8.65 +/- 3.78 vs. 6.46 +/- 3.51 p = 0.02).

CONCLUSIONS

Plasma immunoreactive endothelin concentration is increased in patients with chronic stable angina. The higher levels occur in patients with severe stenoses and total coronary occlusion.

Coronary artery spasm. Multiple causes and multiple roles in heart disease

Myocardial infarction and sudden cardiac death may be initiated by a sudden intense localized contraction of coronary artery smooth muscle. When this event occurs around a vulnerable eccentric lipid-filled plaque, rupture and extrusion of plaque contents and exposure of collagen occur. This may sometimes be a silent and self-limiting event; other times it leads to thrombus formation. A second wave of spasm due to accumulated platelet and inflammatory mediators may compound the contractile consequences of the initiating event. Spasm involves intrinsic smooth muscle cell electrical mechanisms, hyper-responsive cells, and multiple agonists that synergize their actions, and the involvement of each mechanism varies at different times in the sequence of vascular occlusion. Study of spasm requires vascular systems that adequately model coronary artery responses of the ageing human heart. As previously emphasized, tissues obtained postmortem, and when possible from recipients during heart transplants, must be integral to theory building, alongside animal models, despite the experimental limitations such tissues impose. A multidisciplinary approach, at all levels of vascular physiology and pharmacology, will be necessary to understand coronary motor activity and human heart disease.

Raised plasma endothelin in unstable angina and non-Q wave myocardial infarction: relation to cardiovascular outcome

BACKGROUND

Among patients with independent evidence of coronary disease and recent onset unstable angina or non-Q wave myocardial infarction the incidence of subsequent cardiovascular events is high. Markers predictive of adverse cardiac outcome in unstable angina and non-Q wave myocardial infarction need to be defined more accurately. Endothelin-1 is a potent endothelium derived vasoconstrictor peptide that may play a part in the pathophysiology of acute myocardial ischaemia. AIM AND STUDY DESIGN: In a study that specifically identified high risk patients a group of 16 consecutive patients with either unstable angina at rest or non-Q wave myocardial infarction were prospectively investigated to establish whether these conditions are associated with high plasma immunoreactive endothelin and whether endothelin concentration at presentation is related to cardiovascular events within the next 12 weeks. Controls consisted of a group of 40 healthy subjects.

RESULTS

Patients had significantly higher mean (SD) plasma endothelin at presentation than did healthy controls (7.4 (1.1) v 5.0 (1.2) pg/ml, P < 0.0001). At nine weeks plasma endothelin was still significantly higher in those patients who had subsequent cardiovascular events, (n = 9, acute myocardial infarction or refractory angina with electrocardiographic changes and revascularisation procedures, 8.5 (2.6) pg/ml, P < 0.005 v controls) whereas its concentration returned to normal in those patients who had a favourable outcome (n = 7, 5.9 (0.7) pg/ml). Compared with those patients who had an uneventful course, patients with subsequent events had significantly higher plasma endothelin, both at presentation and at nine weeks (P < 0.05 on both occasions).

IMPLICATIONS

Endothelin may contribute to the pathophysiology of acute coronary syndromes and may relate to subsequent cardiovascular outcome.

Role of endothelin in the maintenance of blood pressure in conscious rats with chronic heart failure. Acute effects of the endothelin receptor antagonist Ro 47-0203 (bosentan)

BACKGROUND

Endothelin (ET) is a potent vasoconstrictor, and its concentration is increased in patients with heart failure. The purpose of this study was to investigate the role of endothelin in heart failure by use of a rat model.

METHODS AND RESULTS

Experiments were performed on rats at 1 through 16 weeks after sham operation or coronary artery ligation. Rats with left ventricular end-diastolic pressures > 15 mm Hg were considered to have chronic heart failure (CHF), while the others were considered to have uncomplicated myocardial infarction (MI). There were increased ET-1 concentrations in CHF rats at weeks 1 to 16 (Sham, 20 +/- 0.5 pg/mL, n = 45; CHF, 31 +/- 2 pg/mL, n = 50; P < .001) and transient increases in ET-3 concentrations at week 1 in both the MI and CHF groups. There were no significant increases in big ET-1 concentrations, suggesting an increased conversion of ET-1 from big ET-1 in the CHF group. At weeks 2 through 8, oral administration of the mixed (ETA and ETB) endothelin receptor antagonist bosentan significantly decreased mean arterial pressure in conscious CHF rats, an effect that increased over time. Furthermore, bosentan had an additive effect to the angiotensin-converting enzyme inhibitor cilazapril.

CONCLUSIONS

Endothelin plays a role in the maintenance of blood pressure in CHF rats, as evidenced by the significant reduction in mean arterial pressure after oral administration of bosentan. Therefore, endothelin antagonists may be useful therapeutic agents in the treatment of CHF.

Role of endogenous endothelin in myocardial and coronary endothelial injury after ischaemia and reperfusion in rats: studies with bosentan, a mixed ETA-ETB antagonist

1. Previous studies suggested that endothelin-1 (ET-1) may play a role in myocardial ischaemia and reperfusion. This study was designed to test the effect of a new nonpeptide antagonist of endothelin ETA and ETB receptors, bosentan, on myocardial infarct size, ventricular arrhythmias, and coronary endothelial dysfunction after ischaemia and reperfusion. 2. Anaesthetized male Wistar rats were subjected to 20 min ischaemia (left coronary artery occlusion) followed by 1 h (for the evaluation of coronary endothelial dysfunction) or 2 h (for the evaluation of infarct size) reperfusion, or 5 min ischaemia followed by 15 min reperfusion (for the evaluation of reperfusion arrhythmias). Vascular studies were performed on 1.5-2 mm coronary segments (internal diameter 250-300 microns) removed distal to the site of occlusion and mounted in wire myographs for isometric tension recording. Area at risk and infarct size were determined by Indian ink injection and triphenyl tetrazolium staining, using computerized analysis of enlarged sections after colour video acquisition. 3. Bosentan, administered at a dose which virtually abolished the pressor response to big ET-1 (3 mg kg-1, i.v. before ischaemia) did not affect heart rate, arterial pressure or the rate pressure product before ischaemia, during ischaemia and during reperfusion. Bosentan did not affect the incidence of reperfusion-induced ventricular fibrillation (controls: 86%, n = 14; bosentan: 93%, n = 15), and did not modify infarct size (% of area at risk: controls: 63 +/- 4, n = 10; bosentan: 60 +/- 6, n = 8). Ischaemia followed by reperfusion markedly reduced the endothelium-dependent relaxations to acetylcholine(maximal response: sham: 59 +/- 4%, n = 9; ischaemia-reperfusion: 26+/- 6%, n = 8; P<0.01), characteristic of reperfusion-induced endothelial dysfunction, and this dysfunction was not prevented by bosentan (maximal response to acetylcholine: 25 +/-5%, n = 9; P<0.01 vs sham; P = NS vs ischaemia/reperfusion).4. These experiments suggest that endogenous endothelin does not contribute to myocyte or coronary endothelial injury in this rat model of ischaemia and reperfusion.

Endothelin and myocardial ischemia

Endothelin is a potent vasoconstrictor with a wide range of effects on the heart. Changes in myocardial and circulating levels of endothelin have been described in various experimental models of myocardial ischemia, and in humans with acute myocardial infarction and different forms of angina pectoris. The role played by endothelin in the different states of myocardial ischemia is unclear. However, myocardial damage has been shown to be reduced in several experimental models of myocardial infarction by administering agents that block the action of endothelin. The aim of this review article is to present the current literature concerning the interaction between endothelin and the various forms of myocardial ischemia, and to explore the significance of such interactions.