Coronary Artery Endothelial Function Research Articles

Provocation of Microvessel Spasm by Low-Dose Acetylcholine in Patients with Suspected Coronary Artery Disease

Endothelial dysfunction plays an important role in the pathogenesis of cardiac syndrome X, and intracoronary low-dose acetylcholine infusion is a widely used diagnostic modality for studying the coronary artery endothelial function. The authors herein report 2 cases of cardiac syndrome X with coronary artery endothelial dysfunction and microvessel spasm. The findings of non-invasive testing were positive for ischemia. Coronary angiograms appeared entirely normal in both cases. However, the intracoronary infusion of low-dose (1.5-15 microg/minute) acetylcholine demonstrated an impairment of the coronary blood flow response and consequently provoked an ST-segment elevation in an electrocardiogram. The coronary angiograms showed no spasm in the epicardial arteries. These patients are thus suggested to have cardiac syndrome X with microvessel spasms associated with coronary artery endothelial dysfunction.

Polarized arrest with warm or cold adenosine/lidocaine blood cardioplegia is equivalent to hypothermic potassium blood cardioplegia

Hypothermic depolarizing hyperkalemic (K + 20 mEq/L) blood cardioplegia is the "gold standard" in cardiac surgery. K + has been associated with deleterious consequences, eg, intracellular calcium overload. This study tested the hypothesis that elective arrest in a polarized state with adenosine (400 micromol/L via adenosine triphosphate-sensitive potassium channel opening) and the Na + channel blocker lidocaine (750 micromol/L) as the arresting agents in blood cardioplegia provides cardioprotection comparable to standard hypothermic K + -blood cardioplegia. Anesthetized dogs were placed on cardiopulmonary bypass and assigned to 1 of 3 groups receiving antegrade cardioplegia delivered every 20 minutes for 1 hour of arrest: cold (10 degrees C) K + -blood cardioplegia (n = 6), cold (10 degrees C) adenosine/lidocaine blood cardioplegia (n = 6), or warm (37 degrees C) adenosine/lidocaine blood cardioplegia (n = 6). After an hour of arrest, cardiopulmonary bypass was discontinued, and reperfusion was continued for 120 minutes. Time to arrest was longer with cold and warm adenosine/lidocaine blood cardioplegia (175 +/- 19 seconds and 143 +/- 19 seconds, respectively) compared with K + -blood cardioplegia (27 +/- 2 seconds; P < .001). Postcardioplegia left ventricular systolic function (slope of the end-systolic pressure/dimension relationship) was comparable among the 3 groups (K + -blood cardioplegia, 15.2 +/- 2.1 mm Hg/mm; cold adenosine/lidocaine blood cardioplegia, 15.9 +/- 3.4 mm Hg/mm; warm adenosine/lidocaine blood cardioplegia, 14.1 +/- 2.8 mm Hg/mm; P = .90). Plasma creatine kinase activity in cold and warm adenosine/lidocaine blood cardioplegia was similar to that in K + -blood cardioplegia at 120 minutes of reperfusion (cold adenosine/lidocaine blood cardioplegia, 11.5 +/- 2.1 IU/g protein; warm adenosine/lidocaine blood cardioplegia, 10.1 +/- 0.9 IU/g protein; K + -blood cardioplegia, 7.6 +/- 0.8 IU/g protein; P = .17). Postcardioplegia coronary artery endothelial function was preserved in all groups. Intermittent polarized arrest with warm or cold adenosine/lidocaine blood cardioplegia provided the same degree of myocardial protection as intermittent hypothermic K + -blood cardioplegia in normal hearts.

Ultrasound brachial artery reactivity testing: technical considerations

Ultrasound brachial artery reactivity testing (UBART) is a noninvasive technique for evaluating endothelial function. Endothelial function is characterized by flow-mediated vasodilation of the brachial artery, which is measured by comparing the brachial artery diameter at rest to the diameter after increased forearm blood flow (reactive hyperemia). Brachial artery flow-mediated vasodilation correlates with measures of coronary artery endothelial function and predicts future adverse coronary events.

Long-term effect of combined vitamins e and c on coronary and peripheral endothelial function

ObjectivesWe tested whether long-term administration of antioxidant vitamins C and E improves coronary and brachial artery endothelial function in patients with coronary artery disease (CAD). BackgroundEndothelial function is a sensitive indicator of vascular health. Oxidant stress and oxidized low-density lipoprotein (LDL) impair endothelial function by reducing nitric oxide bioavailability in the artery wall. MethodsWe randomly assigned 30 subjects with CAD to combined vitamin E (800 IU per day) and C (1,000 mg per day) or to placebos in a double-blind trial. Coronary artery endothelial function was measured as the change in coronary artery diameter to acetylcholine infusions (n = 18 patients), and brachial artery endothelial function was assessed by flow-mediated dilation (n = 25 patients) at baseline and six months. Plasma markers of oxidant stress (oxidized LDL and autoantibodies) were also measured. ResultsPlasma alpha-tocopherol (p < 0.001) and ascorbic acid (p < 0.02) increased with active therapy. Compared to placebo, there was no improvement in coronary and brachial endothelial vasomotor function over six months. Although vitamins C and E tended to reduce F2-isoprostanes (p = 0.065), they failed to alter oxidized LDL or autoantibodies to oxidized LDL. ConclusionsLong-term oral vitamins C and E do not improve key mechanisms in the biology of atherosclerosis or endothelial dysfunction, or reduce LDL oxidation in vivo.

Improvement of serum oxidation by pravastatin might be one of the mechanisms by which endothelial function in dilated coronary artery segments is ameliorated

Background: Oxidation susceptibility of lipids in vitro is considered to reflect the exposure of lipids to oxidation stress in vivo which is related to cardiovascular morbidity. This study examined the effect of pravastatin therapy on serum oxidation susceptibility, particularly in relation to endothelial function of coronary arteries. Methods: The participants were recruited from the Pravastatin-Related Effects Following Angioplasty on Coronary Endothelium trial, a double-blinded, placebo-controlled, randomized, multi-center study designed to analyze the effect of parvastatin treatment on endothelial function in previously dilated and normal coronary arteries. Serial, graded, intra-coronary acetylcholine infusions were used to assess endothelial function. In vitro, copper-induced, serum oxidation parameters were determined at randomization and at time of coronary endothelial function assessment. Results: Oxidation parameters were determined in 45 patients (pravastatin 23, placebo 22). Pravastatin therapy significantly improved serum oxidation lag time (+8%, P<0.05), maximal diene formation rate (−22%, P<0.01) and total amount of dienes formed after 5 h (−16%, P<0.01). These parameters remained essentially unchanged in the placebo group. Acetylcholine-evoked responses were positively correlated to therapy-induced change in serum oxidation susceptibility in the dilated segment group ( r 2=0.56, P=0.006). Conclusion: Pravastatin's beneficial effect on endothelial dysfunction of dilated coronary segments may be secondary to pravastatin's improvement of oxidation susceptibility.

Clinical utility of endothelial function testing: ready for prime time?

“…Arteriosclerosis…is the expression of the natural wear and tear to which the tubes are subjected…the onset of arteriosclerosis depends on the quality of arterial tissue (vital rubber)…in the make up of the machine, bad material was used for the tubing…”1 — William Osler, The Principles and Practice of Medicine, 1892 The arterial endothelium comprises cells resting on a basement membrane that exert autocrine, paracrine, and endocrine functions. This monolayer of endothelial cells plays a crucial role in the regulation of vascular tone in part by the release of vasoactive substances, notably NO, endothelin, prostacyclin, and angiotensinogen.2–4 In addition, endothelial cells are involved in the modulation of platelet activation, leukocyte adhesion, and thrombosis. The endothelium, therefore, delicately balances the counterregulatory pathways that control vasomotion, cell proliferation, thrombosis, inflammation, and oxidation. Endothelial function becomes impaired early in the atherogenic process, and this diminishes the normal vasodilator response. Impaired endothelium-dependent vasorelaxation can be detected by measuring the response to pharmacological and physiological stressors before the development of angiographically significant atherosclerotic plaque in the coronary5,6 and peripheral vasculature.7 Well-known cardiac risk factors, including age, gender, hypertension, hyperlipidemia, diabetes mellitus, and smoking, as well as novel risk factors, such as inflammation and hyperhomocystinemia, have been associated with abnormal vasorelaxation. Pharmacological therapies and lifestyle changes aimed at improving cardiovascular risk, in many instances, may also improve vasomotor function.8 Because atherosclerosis is a diffuse disease process, endothelial function can be assessed in either the coronary or the peripheral circulation. Coronary artery endothelial function is most commonly assessed by intracoronary infusion of acetylcholine, which, acting via muscarinic receptors on endothelial cells, causes release of NO and coronary artery dilation. In patients with risk factors for atherosclerosis and in those with overt coronary artery disease, infusion of acetylcholine results in a diminished vasodilatory response …

Contribution of endocannabinoids in the endothelial protection afforded by ischemic preconditioning in the isolated rat heart

The aim of the present study was to assess the contribution of endogenous cannabinoids in the protective effect of ischemic preconditioning on the endothelial function in coronary arteries of the rat. Isolated rat hearts were exposed to a 30-min low flow ischemia (1 ml/min) followed by 20-min reperfusion, after which the response to the endothelium-dependent vasodilator, serotonine (5-HT), was compared with that of the endothelium-independent vasodilator, sodium nitroprusside (SNP). In untreated hearts, ischemia-reperfusion diminished selectively 5-HT-induced vasodilatation, compared with time-matched sham hearts, the vasodilatation to SNP being unaffected. A 5-min zero-flow preconditioning ischemia in untreated hearts preserved the vasodilatation produced by 5-HT. Blockade of either CB 1-receptors with SR141716A or CB 2-receptors with SR144528 abolished the protective effect of preconditioning on the 5-HT vasodilatation. Perfusion with either palmitoylethanolamide or 2-arachidonoylglycerol 15 min before and throughout the ischemia mimicked preconditioning inasmuch as it protected the endothelium in a similar fashion. This protection was blocked by SR144528 in both cases, whereas SR141716A only blocked the effect of PEA. The presence of CB 1 and CB 2-receptors in isolated rat hearts was confirmed by Western blots. In conclusion, the data suggest that endogenous cannabinoids contribute to the endothelial protective effect of ischemic preconditioning in rat coronary arteries.

Inhibitory effect of glucocorticoid on coronary artery endothelial function.

Acute and chronic stresses are implicated in cardiovascular diseases including coronary artery disease. The present study was designed to examine the direct effects of the stress hormone cortisol on nitric oxide (NO) release and endothelial NO synthase (eNOS) expression in cultured bovine coronary artery endothelial cells (BCAEC). Nitrate, nitrite, and NO (NO(x)) were measured by the chemiluminescence method. At 24 h after treatment, cortisol (1 nM-10 microM) produced a dose-dependent decrease in NO(x) release, which was attenuated in the presence of the 11beta-hydroxysteroid dehydrogenase inhibitor carbenoxolone (3 microM). In accordance, eNOS protein levels were significantly decreased by cortisol in a dose-dependent manner. Cortisol pretreatment significantly increased the rate of eNOS protein degradation in the presence of cycloheximide. In addition, cortisol pretreatment decreased ATP-induced intracellular Ca(2+) elevation and NO(x) release in BCAEC. The presence of glucocorticoid receptors in BCAEC was demonstrated by Western blot. The results suggest that cortisol, through activation of glucocorticoid receptors, suppresses NO(x) release in BCAEC by downregulating eNOS proteins and inhibiting intracellular Ca(2+) mobilization. Decreased NO(x) is likely to result in an increase in contraction of coronary arteries, leading to a decrease in coronary blood flow.

Statins and the assessment of endothelial function - reply to Lee et al.

We agree with Lee et al. [1] that noninvasive assessment of endothelial dysfunction requires expensive and specialized equipment (ultrasound system), the presence of a trained observer and, above all, that it is observer dependent. On the other hand, it has been shown that endothelial function of coronary arteries, measured by coronary angiography – which has similar disadvantages to those of the method used in our study [2] – is an independent predictor of atherosclerosis disease progression and of the rate of cardiovascular events, independently of other coronary risk factors in patients with clinical evident coronary artery disease [3]. We may assume that the influence of all atherosclerotic risk factors is mirrored in endothelial (dys)function. Because of this, markers of endothelial dysfunction are actively being sought. Currently, the most promising areas involve the study of endothelium-dependent vasodilation and the detection of circulating markers of endothelial damage [4]. Endothelial injury may result in the release of various factors that can be detected in the circulation and therefore used as potential markers of endothelial dysfunction. Levels of E-selectin, which is expressed only on endothelial cells, were elevated in patients with dyslipidemia, and were shown to decrease after treatment with statins [5]. Proteins involved in haemostasis and synthesized by endothelial cells have been proposed as markers of endothelial dysfunction [4]. The main problem with these markers is their relatively poor specificity, which may hamper their use in diagnostic tests or for monitoring the effects of treatment. Endothelial dysfunction has also been shown in patients with increased levels of homocysteine [6]. For these reasons, we also measured fibrinolytic parameters – tissue plasminogen activator (t-PA) antigen and activity, plasminogen activator inhibitor 1 (PAI-1) antigen and activity, fibrinogen, total and free tissue factor pathway inhibitor (TFPI), homocysteine and the highly sensitive C-reactive protein. In summary, cerivastatin has been shown to have no influence on the level of serum homocysteine, whilst fenofibrate increased it significantly. On the other hand, both drugs decreased serum C-reactive protein levels, with a somewhat higher decrease after cerivastatin. Cerivastatin and fenofibrate differently affected TFPI and PAI-1: cerivastatin decreased the levels of total and free TFPI antigen with no influence on PAI-1, whilst fenofibrate increased PAI-1 but did not affect TFPI. Taken together, these data provide additional information on the role of antiatherogenic mechanisms of these hypolipemic drugs. Further prospective studies, with a larger number of patients, are needed to answer the question as to whether these differences can explain the greater relative risk reduction observed in secondary prevention studies with statin [7], than with fibrate [8].

The Effects of Radiation Using Ho-166 on Endothelial Function in a Porcine Coronary Model

Background and Objectives:It has been reported that intracoronary radiation therapy (ICRT) using a Ho166 coated balloon inhibits restenosis of porcine coronary arteries. However, the consequences of ICRT on coronary artery endothelial function are unknown. The aim of this study is to investigate the effects of ICRT using a Ho-166 balloon on coronary artery endothelial function and vasomotor reactivity. Materials and Methods:Female pigs (25-35 kg) were orally premedicated daily with aspirin (100 mg) and ticlopidine (250 mg) for the duration of the study. Under sterile conditions with local anesthesia of the skin provided by 2% lidocaine, an arteriotomy of the left carotid artery was performed, an 8 Fr sheath was inserted, and intraarterial heparin sodium (10,000 IU) was injected. Under fluoroscopic guidance, the coronary artery main branch was selected through an 8 Fr guiding catheter for coronary artery overdilation injury (balloon to artery ratio, 1.3:1) and ICRT. A Ho-166 coated balloon prepared to deliver 20 Gy at a depth of 2 mm from the balloon surface was used for ICRT. The coronary artery main branch in each pig was randomly assigned to either balloon injury (Group I) or balloon injury plus ICRT (Group II). Coronary artery segments were taken from the animals at 0 week (n=8), 4 weeks (n=6) and 8 weeks (n=8) after the intervention. Data in each group denote the relative ratio compared to non-injured coronary artery and are expressed as mean±standard error of mean. Results:The degree of KCl-induced contractile response (g) was not different between the two groups at 0 and 4 weeks, but was significantly decreased in group II compared to group I at 8 weeks (I:1.04 논문접수일:2001년 11월 20일 심사완료일:2002년 1월 29일 교신저자:정명호, 501-757 광주광역시 동구 학1동 8번지 전남대학교병원 심장센터 전화:(062) 220-6243·전송:(062) 228-7174·E-mail:myungho@chollian.net

Electroplegia: an alternative to blood cardioplegia for arresting the heart during conventional (on-pump) cardiac operation

Background. Aortic cross-clamping is contraindicated in patients with severe atherosclerosis of the ascending aorta, and administration of chemical cardioplegia may be cumbersome in these patients. In this study, we demonstrate an alternative method of achieving cardioplegia by electrical stimulation of the vagus nerve. Methods. In anesthetized canines, the left anterior descending coronary artery was reversibly ligated for 90 minutes, followed by cardiopulmonary bypass (CPB) and randomization to three groups (n = 8 each): (1) BCP group: 1 hour of intermittent hypothermic (4°C) blood cardioplegia infusion; (2) CPB group: 1 hour of CPB alone; (3) EP group (group receiving electroplegia): 1 hour of intermittent vagal stimulation (total of 60 20-second electrical stimuli at 40 Hz, 6 to 10 V) with adjunctive pyridostigmine (0.5 mg/kg), verapamil (50 μg/kg), and propranolol (80 μg/kg) to potentiate hyperpolarization and suppress ectopic escape beats. Results. The EP group achieved consistent intervals of arrest with 3.8 ± 1.2 escape beats per 20-second stimulation period. After 2 hours of reperfusion off CPB, the left anterior descending coronary artery segmental shortening was reduced from baseline in all groups, but the segmental shortening recovered to a greater extent in the EP group than in either the CPB or BCP group (2.4% ± 1.4% versus −1.3% ± 1.3% versus −4.0% ± 0.8%, p < 0.05). Infarct size (TTC stain, percentage of area at risk) was comparable among groups (EP: 20.9% ± 4.7%; CPB: 29.6% ± 3.2%; BCP: 25.1% ± 5.7%). Postischemic left anterior descending coronary artery endothelial function (percent maximum relaxation to acetylcholine) was depressed in the EP group (68.6% ± 7.6% versus 102.3% ± 6.4%, p < 0.05), but was comparable versus nonischemic circumflex function in the BCP group (77.1% ± 11.9% versus 100.4% ± 10.0%, p = 0.15) and the CPB group (93.8% ± 6.6% versus 93.3% ± 6.6%). Conclusions. Electroplegia achieves elective intermittent cardiac arrest, avoids hypothermia, chemical cardioplegia, and aortic cross-clamping, with physiological outcomes comparable to blood cardioplegia.

Improvement of coronary artery endothelial dysfunction with lipid-lowering therapy: heterogeneity of segmental response and correlation with plasma-oxidized low density lipoprotein

OBJECTIVESThis study assessed coronary artery endothelial function in patients with hypercholesterolemia before and after lipid lowering, using quantitative angiography to examine the acetylcholine (Ach) response along the entire analyzable vessel.BACKGROUNDLipid lowering reverses endothelial dysfunction, but whether improvement occurs only in some segments and not others has not been established. Statistical correlation of improvement with specific lipid moieties remains undefined.METHODSQuantitative angiography was performed after Ach (10−6, 10−5, 10−4M) in 29 patients with coronary atherosclerosis before and 18 ± 5.2 months after lipid-lowering treatment (statins, bile sequestrant resins). Standard lipid moieties and markers of oxidized low density lipoprotein (LDL) (immunoglobulin G and M autoantibody titers to malondialdehyde-LDL, E06 epitope) were measured serially.RESULTSPre-treatment of the vessel diameters at control and with 10−6M, 10−5M and 10−4M Ach were 2.108 ± 0.085, 2.086 ± 0.087, 2.069 ± 0.084 and 1.963 ± 0.097 mm (M ± SE), respectively, and increased at follow-up to 2.139 ± 0.094, 2.119 ± 0.086, 2.127 ± 0.084 and 2.080 ± 0.085 mm (p < 0.0001). Improvement in the most constricted and modest declination in the more dilated segments were observed. Change in the E06 and Apolipoprotein A-1 titers correlated with improved vasomotion (p = 0.027 and 0.005, respectively). The pre- and post-treatment levels of the E06 epitope, as well as the post-treatment IgM autoantibody titer to MDA-low density lipoprotein, also correlated (p < 0.028, < 0.001 and p < 0.004, respectively).CONCLUSIONSDrug treatment reverses endothelial dysfunction, but the effect is heterogeneous. Most coronary segments show enhancement, while others show declination of dilation, underscoring the importance of assessing the entire analyzable artery. Improvement in vasomotion correlates most significantly with markers of plasma-oxidized low-density lipoprotein.

Cholesterol Lowering With Pravastatin Improves Resistance Artery Endothelial Function: Report of Six Subjects With Normal Coronary Arteriograms

Improvement in coronary artery endothelial function has been demonstrated after cholesterol lowering in hypercholesterolemic patients with significant atherosclerosis. However, to our knowledge, no previous study has shown improvement in resistance artery function in subjects with normal coronary arteries after cholesterol lowering. The purpose of our study was to investigate the effect of cholesterol lowering with pravastatin on coronary resistance artery endothelial function in the setting of angiographically normal coronary arteries. Invasive testing of coronary endothelial and vasomotor function was performed at baseline and after 6 months of pravastatin treatment in six patients with normal coronary arteriograms. After 6 months of pravastatin treatment, low-density lipoprotein cholesterol level dropped from 157+/-11 to 117+/-8 mg/dL (p = 0.02) and percent increase in coronary blood flow after acetylcholine improved from 97+/-13% to 160+/-16% (p = 0.01). There was a trend (p = 0.17) toward enhanced epicardial dilation in response to acetylcholine after pravastatin treatment when compared with the baseline study. Our study demonstrates significant improvement in coronary resistance artery endothelial function after 6 months of cholesterol lowering with pravastatin in six subjects presenting with chest pain who were found to have normal coronary arteriograms. A trend toward improved epicardial vasomotion was also observed.

Hypercholesterolemia increases coronary endothelial dysfunction, lipid content, and accelerated atherosclerosis after heart transplantation.

Hyperlipidemia may increase endothelial damage and promote accelerated atherogenesis in graft coronary vasculopathy. To study the effects of hypercholesterolemia on coronary endothelial dysfunction, intimal hyperplasia, and lipid content, a porcine model of heterotopic heart transplantation, allowing nonacute rejection without immunosuppressive drugs, was used. A high cholesterol diet was fed to donor and recipient swine 1 month before and after transplantation. The endothelial function of coronary arteries of native and transplanted hearts from cholesterol-fed animals was studied in organ chambers 30 days after implantation and compared with endothelial function in arteries from animals fed a normal diet. The total serum cholesterol increased 3-fold in donors and recipients. Endothelium-dependent relaxations to serotonin, to the alpha(2)-adrenergic agonist UK14,304, and to the direct G-protein activator sodium fluoride were decreased significantly in allografted hearts compared with native hearts from both groups. Relaxations to the calcium ionophore A23187 and bradykinin were decreased significantly in allografts from animals fed the high cholesterol diet. The prevalence of intimal hyperplasia was significantly increased in coronary arteries from hypercholesterolemic swine. There was a significant increase in the lipid content of allograft arteries of hypercholesterolemic recipients. Hypercholesterolemia causes a general coronary endothelial dysfunction, increases the prevalence of intimal hyperplasia, and augments the incorporation of lipids in the vascular wall after heart transplantation. Hyperlipidemia accelerates graft coronary atherosclerosis through its effects on the endothelium.

The assessment of endothelial function in the cardiac catheterization laboratory in patients with risk factors for atherosclerotic coronary artery disease.

In the last 2 decades the endothelium has emerged as an active modulator of many local and systemic functions. The intact endothelium synthesizes and releases a variety of autocrine and paracrine substances that affect cell growth and proliferation, platelet aggregation and adhesion, inflammatory processes, and vascular tone. The aims of the present review are to present the current technique for the assessment of coronary artery endothelial function in the cardiac catheterization laboratory and to describe the current knowledge regarding risk factor modification on endothelial dysfunction.

Endothelium-dependent flow-mediated vasodilation in coronary and brachial arteries in suspected coronary artery disease

Previous studies showed a weak correlation between endothelial function of the coronary arteries as assessed by acetylcholine and brachial artery vasomotion during reactive hyperemia. When the same stimulus was used, we obtained a strong correlation between flow-mediated dilation in the coronary and brachial arteries (r=0.78, p <0.001), so that noninvasive assessment of flow-mediated dilation in the brachial artery could be used as a surrogate measure for coronary artery endothelial function.

Role of kinins in the endothelial protective effect of ischaemic preconditioning.

1. The aim of this study was to assess whether the protective effect of ischaemic preconditioning on endothelial function in coronary arteries of the rat involves kinins. 2. Isolated hearts of the rat were exposed to a 30-min low-flow ischaemia (flow rate of 1 ml min[-1]) followed by 20-min reperfusion, after which coronaries were precontracted with 0.1 microM U-46619, and the response to the endothelium-dependent vasodilator, 5-hydroxytryptamine (5-HT, 10 microM), compared to that of the endothelium-independent vasodilator, sodium nitroprusside (SNP, 3 microM). 3. In untreated hearts, ischaemia-reperfusion diminished selectively 5-HT-induced vasodilatation, compared with time-matched sham hearts. The vasodilatation to SNP was unaffected after ischaemia-reperfusion. Preconditioning (5 min of zero-flow ischaemia followed by 10 min reperfusion) in untreated hearts preserved the vasodilatation produced by 5-HT. 4. Blockade of B1 and B2 receptors with either 3 nM [Lys[0], Leu8, des-Arg9]-bradykinin (LLDBK) or 10 nM Hoe 140 (icatibant), respectively, (started 15 min before ischaemic preconditioning or a corresponding sham period and stopped just before the 20-min reperfusion period) had no effect on the vasodilatation produced by either 5-HT or SNP in sham hearts. Pretreatment with Hoe 140 did not block the protective effect of ischaemic preconditioning on the 5-HT vasodilatation. In contrast, LLDBK halved the protective effect of ischaemic preconditioning on endothelium-dependent vasodilatation. 5. Perfusion with either bradykinin or des-Arg9-bradykinin (1 nM) 30 min before and lasting throughout the ischaemia protected the endothelium. 6. In conclusion, ischaemic preconditioning affords protection to the endothelial function in coronary resistance arteries of the rat partly by activation of B1 receptors. Although exogenous BK perfusion can protect the endothelium, B2 receptors do not play an important role in this protection in the rat isolated heart.

Protection afforded by preconditioning to the diabetic heart against ischaemic injury

The aim of this study was to assess whether the cardioprotective effect of ischaemic preconditioning (IPC) on endothelial function in coronary arteries and myocardial function is affected in the streptozotocin-induced diabetic rat heart. Isolated hearts, perfused under constant flow conditions, were exposed to 30 min of partial ischaemia (flow rate 1 ml min-1) followed by 20 min of reperfusion. In the diabetic group (without ischaemia or IPC), infusion of 10 microM serotonin (5-HT), an endothelium-dependent, and 3 microM sodium nitroprusside (SNP), an endothelium-independent vasodilator, in the coronary bed preconstricted with 0.1 microM U-46619 induced a marked vasodilation. Ischaemia, either without or with preconditioning with a single 5 min ischaemia and 10 min reperfusion (IPC1) before ischaemia, was accompanied by a reduced 5-HT-induced vasodilation in diabetic hearts. In contrast, IPC1 preserved the response to 5-HT in non-diabetic hearts. A more extensive IPC with 3 periods of 5 min ischaemia followed by 5 min reperfusion (IPC3) preserved the vasodilation produced by 5-HT in both diabetic and non-diabetic hearts. IPC3 increased the recovery of d P/dtmax and d P/dtmin during the 30 min ischaemic period and during reperfusion in all hearts. In contrast, IPC1 had no effect on myocardial recovery in either groups. Adenosine pre-treatment started 30 min before ischaemia mimicked IPC3, preserving the vasodilation to 5-HT and improving myocardium recovery in both groups. When adenosine was started 15 min before ischaemia, vasodilation to 5-HT was preserved in non-diabetic hearts only. These results suggest that IPC affords protection to endothelial function in resistance coronary arteries of diabetic hearts. To achieve this protection, a more extensive IPC is needed, which may be related to a longer exposure to adenosine.

Time Dependence of Endothelium-Mediated Vasodilation by Intermittent Antegrade Warm Blood Cardioplegia

The technique of intermittent antegrade warm blood cardioplegia (IAWBC) exposes the heart to brief periods of normothermic ischemia. This may impair endothelial function in coronary arteries. Three cardioplegic technique were tested in porcine hearts arrested for 32 to 36 minutes and reperfused for 30 minutes: IAWBC, antegrade cold blood cardioplegia (ACBC), and antegrade cold crystalloid cardioplegia (ACCC). In the hearts arrested with IAWBC, three different intervals of ischemia were used: three 10-minute intervals (IAWBC1), two 15-minute intervals (IAWBC2), and one 30-minute interval (IAWBC3). Rings from the coronary arteries were used to evaluate in vitro the contractile responses to U46619 and the relaxant responses to bradykinin, A23187, and sodium nitroprusside. All six groups (treatment groups and control group) displayed similar responses to U46619 (30 nmol/L) and nitroprusside. In the IAWBC1, IAWBC2, AND ACBC groups, endothelium-dependent relaxations to bradykinin and A23187 were preserved compared with controls, whereas those of the ACCC and IAWBC3 groups were significantly impaired (bradykinin: control, 8.72 +/- 0.07; IAWBC1, 8.73 +/- 0.03; IAWBC2, 8.65 +/- 0.05; IAWBC3, 8.30 +/- 0.07 [p < 0.05]; ACBC, 8.50 +/- 0.03; ACCC, 8.25 +/- 0.09 [p < 0.05]; A23187: control, 7.07 +/- 0.08; IAWBC1, 7.07 +/- 0.06; IAWBC2, 7.04 +/- 0.03; IAWBC3, 6.64 +/- 0.01 [p < 0.05]; ACBC, 6.80 +/- 0.05; ACCC, 6.60 +/- 0.08 [p < 0.05]; nitroprusside: control, 6.19 +/- 0.1; IAWBC1, 6.19 +/- 0.07; IAWBC2, 6.03 +/- 0.03; IAWBC3, 6.08 +/- 0.05; ACBC, 6.04 +/- 0.2; ACCC, 6.05 +/- 0.03; all values are expressed as the negative logarithm of the concentration producing 50% of the maximal response). Myocardial preservation with IAWBC with ischemic intervals of 15 minutes or shorter does not alter the endothelium-dependent relaxation to bradykinin or A23187 in porcine coronary arteries, but these responses are significantly impaired by ACCC and IAWBC with an ischemic interval of 30 minutes.

Protective effect of reduced glutathione on endothelial function of coronary arteries subjected to prolonged cold storage.

Endothelial dysfunction can play a key role in early no reflow and late accelerated cardiac graft arteriosclerosis. We studied the direct effect of reduced glutathione (GSH) on the preservation of endothelial function of coronary arteries subjected to prolonged cold storage. Ring preparations were dissected from rat left coronary arteries and mounted on an isometric wire myograph. After control measurements, artery segments were exposed to 15 hr of hypothermic (+4 degrees C) incubation in either normal saline (group 1), GSH-free Celsior solution (a new heart preservation solution) (group 2), or Celsior solution with 3 mmol/L of GSH (group 3). After storage, the basal tone was increased in groups 1 and 2, but it did not change in group 3. The endothelium-dependent relaxation to acetylcholine was reduced in groups 1 and 2, but it was not affected in group 3. The sensitivity to acetylcholine was decreased in group 1, and there were no changes in groups 2 and 3. Our data suggest that fresh GSH in Celsior solution improves preservation of coronary endothelial function.