Hyperventilation as a specific test for diagnosis of coronary artery spasm

The hyperventilation test has been used as a clinical tool to induce coronary spasm. However, its diagnostic and prognostic values have not been fully elucidated. This study was designed to establish the sensitivity and specificity of the hyperventilation test and to clarify the characteristics of hyperventilation test-positive patients. We examined 206 patients in whom coronary spasm was documented by angiography (spasm group), and 183 patients without angina at rest in whom acetylcholine failed to induce spasm (nonspasm group). All patients performed vigorous hyperventilation for 6 minutes in the early morning. Of the spasm group patients, 127 showed positive responses to the test, including ST elevation (n = 111), ST depression (n = 15) and negative U wave (n = 1). None in the nonspasm group showed any ischemic electrocardiographic change. Thus, the sensitivity and specificity of this test for diagnosis of coronary spasm were 62% and 100%, respectively. In the spasm group, there were no significant differences between hyperventilation test-positive and test-negative patients in age, sex, the prevalence of hypertension, diabetes mellitus, obesity, smoking, and the number of diseased vessels. When clinical characteristics were compared, the proportions of the patients with high disease activity (> or =5 attacks a week), with severe arrhythmias (second- or third-degree atrioventricular block and/or ventricular tachycardia) during attacks, and with multivessel spasm were significantly higher in the hyperventilation test-positive patients than in the negative patients (69% vs 20%, p <0.0001; 31% vs 11%, p <0.005; and 58% vs 34%, p <0.01, respectively). These findings imply that hyperventilation is a highly specific test for the diagnosis of coronary artery spasm, and that hyperventilation test-positive patients are likely to have life-threatening arrhythmias during attacks and multivessel spasm.

Long-lasting abnormalities in cardiac sympathetic nervous system in patients with coronary spastic angina: quantitative analysis with iodine 123 metaiodobenzylguanidine myocardial scintigraphy

Quantitative analysis of iodine 123 metaiodobenzylguanidine (MIBG) myocardial tomographic imaging showed that the regional uptake reduction and abnormally high washout of MIBG in the myocardial territories of the coronary artery with spasm were observed in 33 (75%) and in 30 (68%) of 44 patients with coronary spastic angina, whereas it was observed in two (7%) and in four (15%) of 27 control subjects, respectively. The patients with higher disease activity of the anginal attack and those with life-threatening ventricular arrhythmias were frequently associated with either the uptake reduction or the abnormally high washout of MIBG (91% in patients with high disease activity, 100% in patients with ventricular arrhythmias). The repeated studies of MIBG myocardial tomographic imaging at 2 and 6 months after suppression of anginal attacks by medical treatments showed that the scintigraphic abnormalities still remained in 85% of the patients at 2 months and 32% at 6 months. Thus the abnormalities in sympathetic nervous system assessed with MIBG scintigraphy has been shown to be highly associated with patients with coronary arteries with spasm, particularly high-risk patients, and lasted for several months despite suppression of anginal attack.

Impairment of endothelium-dependent relaxation of rabbit aortas by cigarette smoke extract--role of free radicals and attenuation by captopril

The aim of this study was to examine the effects of the water soluble component of cigarette smoke extract (CSE) on endothelium-dependent relaxation (EDR) of isolated rabbit aortas. The incubation with CSE was found to inhibit EDR in a dose-dependent manner. Co-incubation of the aortic strips with superoxide dismutase (SOD), N-acetylcysteine, glutathione or dimethyl sulfoxide (DMSO), free radical scavengers, attenuated the CSE-induced inhibition of the arterial relaxation. Co-incubation of the strips with captopril (3 mM), an angiotensin converting enzyme inhibitor, also attenuated CSE-induced impairment of vasorelaxation. In parallel experiments using cultured human endothelial cells, CSE suppressed endothelial release of NOx, stable metabolites of nitric oxide (NO). SOD, DMSO and captopril attenuated the suppression of NO production by CSE in association with reduction of free radicals, superoxide anions and hydroxyl radicals, in CSE solution. Neither lactate dehydrogenase release from the cultured endothelial cells nor cell death estimated by trypan blue exclusion test was found after the incubation of the cultured endothelial cells with CSE. The results indicate that free radicals in CSE induce the impairment of EDR, which may be partly due to suppression of NO production and is not due to non-specific cytotoxicity by CSE. Captopril attenuates CSE-induced endothelial dysfunction partly through scavenging free radicals.

Supersensitive dilator response to nitroglycerin but not to atrial natriuretic peptide in spastic coronary arteries in coronary spastic angina

It has been shown that there is the supersensitivity of the dilator effect of nitrovasodilators in the coronary arteries of patients with coronary spastic angina. This study was aimed to elucidate its mechanism(s) by examination of dilator response of spastic coronary arteries to atrial natriuretic peptide (ANP), which is known to dilate arteries by the same final common pathway through cyclic guanosine monophosphate (cGMP) as nitrovasodilators. Effects of infusion of nitroglycerin and ANP on epicardial coronary diameter of left coronary arteries were thus examined by quantitative coronary angiography in 20 patients with coronary spastic angina, who had spasm in left coronary arteries, and in 27 control subjects. Dilator response of coronary diameter to intracoronary infusion of ANP (0.5 microgram/kg) was found to be comparable between spastic coronary arteries and control arteries, whereas dilator response to nitroglycerin (250 micrograms) was enhanced in the spastic arteries compared with control arteries. The results indicate that spastic coronary arteries exhibit supersensitive dilator response to nitroglycerin but not to ANP. There is a possibility that dilator response to cGMP may be comparable between spastic and control coronary arteries and that soluble guanylate cyclase activity and/or conversion of nitric oxide bio-activity from nitroglycerin may be enhanced in spastic coronary arteries.

Flow-mediated, endothelium-dependent dilatation of the brachial arteries is impaired in patients with coronary spastic angina

Coronary spasm is induced by acetylcholine, serotonin, ergonovine, or histamine, all of which cause vasodilation when the endothelium is intact, and is promptly relieved by nitroglycerin, which vasodilates through the direct action on smooth muscle. Endothelial dysfunction is therefore possibly involved in the pathogenesis of coronary artery spasm. The aim of this study was to determine whether endothelium-dependent vasodilation is impaired in the peripheral arteries of patients with coronary spastic angina. Flow-dependent vasodilation of the brachial arteries during reactive hyperemia after the transient arterial occlusion was examined by using the high-resolution ultrasound technique in 35 patients with coronary spastic angina and 35 controls. Flow-dependent vasodilation of the brachial arteries was impaired in patients with coronary spastic angina compared with controls (5.9% +/- 4.2% vs 9.6% +/- 3.4%, p < 0.001) although the percent increase in blood flow during reactive hyperemia was not different between the two groups. The dilator response to nitroglycerin was preserved in patients with coronary spastic angina compared with controls (18.6% +/- 5.1% vs 16.2% +/- 3.9%, p < 0.04). The results indicate that endothelium-dependent vasodilation of the brachial arteries is impaired in patients with coronary spastic angina. Thus endothelial vasomotor dysregulation may also be present in the systemic arteries as well as coronary arteries in patients with coronary spastic angina.

Deficiency in nitric oxide bioactivity in epicardial coronary arteries of cigarette smokers

OBJECTIVES

This study sought to examine nitric oxide-mediated regulation of epicardial coronary arterial tone in cigarette smokers.

BACKGROUND

Cigarette smoking is a major risk factor for coronary artery disease and is highly prevalent in patients with coronary spastic angina. Long-term exposure to cigarette smoking has been recently reported to suppress endothelium-dependent arterial relaxation in vivo humans.

METHODS

Responses of epicardial coronary artery diameter to single or combined infusion of acetylcholine and NG-monomethyl-L-arginine (L-NMMA) into the left main coronary artery were examined in 11 current smokers and 17 nonsmokers using quantitative coronary angiography.

RESULTS

Acetylcholine dilated one-third of the proximal segments and most of the distal segments of coronary arteries in nonsmokers, whereas it constricted most of the proximal and distal segments in smokers. L-NMMA decreased the basal diameter of coronary arteries in nonsmokers but had minimal effect on the basal diameter in smokers. L-NMMA abolished the dilator response to acetylcholine in the coronary arteries of nonsmokers but had minimal effect on the constrictor response to acetylcholine in the arteries of smokers. The dilator response to nitroglycerin was significantly increased in the coronary arteries of smokers compared with in those of nonsmokers. The constrictor response to L-NMMA at rest was significantly correlated with the dilator response to nitroglycerin and with the diameter changes to acetylcholine in both smokers and nonsmokers.

CONCLUSIONS

Nitric oxide bioactivity at rest and at acetylcholine-stimulated conditions in smokers was decreased, leading to the supersensitivity of the artery to the dilator effect of nitroglycerin as well as the constrictor effect of acetylcholine in smokers. Cigarette smoking affects nitric oxide-mediated regulation of coronary artery tone.

Menstrual cyclic variation of endothelium-dependent vasodilation of the brachial artery: possible role of estrogen and nitric oxide

Estrogens have been reported to influence endothelial functions. This article's aim is to examine whether endothelium-dependent vasodilation of brachial arteries is changed in parallel with the physiological variation of the ovarian hormones during the menstrual cycle in young healthy female subjects. With high-resolution ultrasonography, we measured the diameter and blood flow of brachial arteries at rest, during reactive hyperemia, and after sublingual nitroglycerin administration in 15 young healthy female subjects (mean 29.6 +/- 2.6 years). All female subjects were studied in each of three different phases of one menstrual cycle (M, menstrual phase; F, follicular phase; L, luteal phase). The increase in arterial diameter during reactive hyperemia was lowest in the menstrual phase and highest in the follicular phase (4.9 +/- 0.8% in M; 14.1 +/- 0.9% in F; 9.2 +/- 1.1% in L; p < 0.005 between any two means among the groups). No significant difference was apparent in the percentage of increase in blood flow during reactive hyperemia among the three phases. The percentage of increase in arterial diameter after nitroglycerin administration also was not significantly different among the three phases of the cycle. The serum estradiol level was lowest in the menstrual phase and was highest in the follicular phase (17.5 +/- 1.6 pg/ml in M, p < 0.0005, M versus F and L; 107.8 +/- 18.0 pg/ml in F, p < 0.05, F versus L; 74.4 +/- 7.3 pg/ml in L). The serum level of nitrite-nitrate, measured by the Griess reaction, was highest in the follicular phase and was lowest in the menstrual phase of the three different phases (40.4 +/- 7.9 mumol/l in M, p < 0.01, M versus F, and p < 0.05, M versus L; 106.7 +/- 17.6 mumol/l in F, p < 0.05, F versus L; 62.2 +/- 6.2 mumol/l in L). In conclusion, a significant variation of the endothelium-dependent vasodilation parallels the levels of serum estradiol and nitrite-nitrate during the menstrual cycle in female subjects.

Role of adenosine in pathogenesis of syndrome X: assessment with coronary hemodynamic measurements and thallium-201 myocardial single-photon emission computed tomography

OBJECTIVES

This study was performed 1) to examine the role of adenosine in the pathogenesis of syndrome X in patients with this syndrome and abnormal results on myocardial scintigrams during exercise, and 2) to determine the susceptibility to myocardial ischemia in this subset of patients with syndrome X.

BACKGROUND

A role for adenosine in the pathogenesis of syndrome X has recently been postulated, but there are few clinical data supporting this hypothesis.

METHODS

Exercise thallium-201 myocardial scintigraphy after intravenous administration of aminophylline, an adenosine receptor blocking agent, or saline solution and adenosine thallium-201 scintigraphy were performed in 26 patients with syndrome X. Hemodynamic variables during exercise and perfusion defect size after aminophylline and saline infusions were compared. At cardiac catheterization, coronary hemodynamic variables during separate infusions of adenosine and doubutamine were also examined and were compared among patients with abnormal or normal scintigrams and 10 control subjects.

RESULTS

Perfusion abnormalities on exercise-thallium-201 scintigraphy occurred in 14 of 26 patients with syndrome X. Intravenous infusion of aminophylline suppressed the scintigraphic perfusion defect and prolonged the time to 1-mm ST segment depression in patients with syndrome X with abnormal exercise scintigrams. Intravenous infusion of adenosine induced a perfusion defect in the same myocardial area where the perfusion defect was observed at exercise in 7 of the 14 patients with syndrome X. At cardiac catheterization, patients with syndrome X with abnormal exercise scintigrams had lower coronary flow reserve and a greater frequency of myocardial lactate production and ST segment depression in response to the infusions of adenosine and doubtamine than did the other two groups. During adenosine infusion, great cardiac vein blood flow and oxygen content were significantly increased and myocardial oxygen consumption and lactate extraction were significantly reduced from baseline without a significant increase in rate-pressure product in this subset of patients with syndrome X.

CONCLUSIONS

Patients with syndrome X with abnormal exercise scintigrams have high susceptibility to myocardial ischemia during exercise or pharmacologic stress tests, probably owing to reduced coronary flow reserve. A heterogeneous response to endogenous adenosine may contribute to scintigraphic perfusion abnormalities and myocardial ischemia during exercise in this subset of patients with syndrome X.

Nitric oxide activity is deficient in spasm arteries of patients with coronary spastic angina

BACKGROUND

Coronary spasm can be induced by acetylcholine, serotonin, ergonovine, or histamine, all of which cause vasodilation when the endothelium is intact by releasing nitric oxide (NO). Coronary spasm is promptly relieved by nitroglycerin, which vasodilates through its conversion to NO. It is thus possible that NO release may be deficient in the spasm arteries in patients with coronary spastic angina (CSA). The aim of this study was to determine whether NO release is deficient in coronary arteries of patients with CSA.

METHODS AND RESULTS

NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, was infused into coronary arteries in 21 patients with coronary spastic angina (CSA) and in 28 control patients. Coronary spasm was induced by intracoronary injection of acetylcholine and was documented angiographically in all patients with CSA. L-NMMA dose-dependently decreased basal luminal diameter of coronary arteries in control patients, whereas it had no effect on basal diameter of the spasm arteries in patients with CSA. L-NMMA abolished the dilator response to acetylcholine and enhanced the constrictor response to acetylcholine in control arteries, whereas it had no effect on the constrictor response to acetylcholine in spasm arteries. Intracoronary infusion of L-arginine did not affect the diameter of spasm or control arteries. The dilator response to nitroglycerin was increased markedly in spasm arteries compared with control arteries, whereas response to diltiazem did not differ between them.

CONCLUSIONS

There is a deficiency in endothelial NO activity in spasm arteries, which leads to the supersensitivity of the artery to the vasodilator effect of nitroglycerin and to the vasoconstrictor effect of acetylcholine in patients with CSA. This deficient endothelial NO activity plays an important role in the pathogenesis of coronary spasm.

Suppression of atherosclerotic changes in cholesterol-fed rabbits treated with an oral inhibitor of neutral endopeptidase 24.11 (EC 3.4.24.11)

Neutral endopeptidase 24.11 (NEP), widely distributed in the body, hydrolyzes and inactivates a number of endogenous vasoactive peptides, some of which could alter various functions of cells present in the arterial wall. Recently NEP has been found to exist in the vascular endothelium. The aim of this study was to assess the influence of chronic NEP inhibition by daily administration of UK79300 (candoxatril), an orally active NEP inhibitor (NEPI), on the development of atherosclerotic changes in high-cholesterol-fed rabbits. Male New Zealand White rabbits were fed for 8 weeks as follows: normal rabbit diet (Normal, n = 15), 1.5% cholesterol diet (Cholesterol, n = 15), or 1.5% cholesterol diet containing NEPI (20 mg.kg-1.d-1) (Cholesterol+NEPI, n = 15). At the end of the dietary period, NEPI treatment was found to suppress the surface area of the aorta covered by plaques (% surface area: Cholesterol, 59 +/- 6 versus Cholesterol+NEPI, 36 +/- 7, P < .01) and decreased contents of cholesterol and cholesterol esters in the aortas. NEPI also reduced plasma total cholesterol by 27% of Cholesterol rabbits (1781 +/- 130 mg/dL). The endothelial function, estimated by the endothelium-dependent relaxation of the isolated aortas in response to acetylcholine, was preserved in Cholesterol+NEPI rabbits compared with that in Cholesterol rabbits. NEP enzymatic activities in plasma and the particulate fraction of the homogenates from the aortas in Cholesterol rabbits were both increased, 3.1- and 3.9-fold, respectively, above those in Normal rabbits, but the activities in Cholesterol+NEPI rabbits were significantly lower than those in Cholesterol rabbits. UK73967, an active form of UK79300, or phosphoramidon partly reversed the atherosclerotic impairment of relaxation of the isolated thoracic aortic rings from Cholesterol rabbits in response to exogenous additions of C-type natriuretic peptide (CNP) and substance P, which are NEP substrates known to exist endogenously in the vascular endothelium. The results suggest that the increased NEP activity plays a significant role in atherogenesis, and NEPIs might be therapeutically useful in the prevention of atherosclerosis. Reduction of plasma cholesterol and suppression of degradations in the arteries of endogenously released CNP, substance P, or possibly other kinins known to have anti-atherosclerotic actions may at least partially contribute to the inhibitory effects of NEPIs on atherosclerotic changes.

Effects of sphingomyelinase and sphingosine on arterial vasomotor regulation

The sphingomyelin pathway is an important signal transduction system regulating various cellular functions. However, little is known about the effect of sphingomyelin metabolites on vasomotor function. We examined the vascular effects of sphingomyelin, sphingosine, and sphingomyelinase (SPMase) in vitro. In pig coronary rings precontracted with prostaglandin F2 alpha, sphingosine and SPMase evoked initial contraction and subsequent gradual relaxation; however, sphingomyelin did not influence the tone. The initial contractions in response to either SPMase (40 microU/ml to 0.4 U/ml) or sphingosine (0.5-10 microM) treatment were abolished in rings denuded of endothelium. This initial contraction in response to sphingosine treatment was significantly attenuated by a cyclo-oxygenase inhibitor indomethacin, but not altered by either a nitric oxide synthase inhibitor, N omega-monomethyl-L-arginine (L-NMMA), a protein kinase C (PKC) inhibitor staurosporine, or superoxide dismutase (SOD, 100 U/ml). Incubation of coronary rings with sphingosine (10 microM) or SPMase (0.4 U/ml) for 120 min significantly attenuated subsequent endothelium-dependent relaxation in response to thrombin and A23187, but did not affect endothelium-independent relaxation in response to sodium nitroprusside. In contrast, sphingomyelin (10 microM) did not alter the endothelium-dependent relaxation. In conclusion, in the sphingomyelin pathway, sphingosine induces vasoconstriction in coronary arteries that seems to be mediated by the release of cyclooxygenase-sensitive vasoconstrictor prostanoids from the endothelium. Sphingosine also induced endothelial dysfunction characterized by impaired endothelium-dependent relaxation. Thus, the sphingomyelin pathway may be an important regulator of vascular function.

Increased plasma levels of B-type natriuretic peptide in patients with unstable angina

This study was designed to examine the plasma levels of B-type or brain natriuretic peptide (BNP), as well as A-type or atrial natriuretic peptide (ANP) in patients with unstable angina as compared with those in patients with stable exertional angina and control subjects. We measured the plasma levels of BNP and ANP in 33 patients with unstable angina, 20 patients with stable exertional angina, and 20 control subjects. The plasma levels of BNP were significantly increased in patients with unstable angina compared with those in patients with stable exertional angina and control subjects, respectively (39.5 +/- 29.4 pg/ml vs 15.1 +/- 8.0 pg/ml; p < 0.01 and 39.5 +/- 29.4 pg/ml vs 10.3 +/- 6.4 pg/ml; p < 0.01, respectively). On the other hand, there was no significant difference in the plasma levels of ANP among the three groups. Furthermore, in patients with unstable angina, the plasma levels of BNP decreased significantly after the medical treatment (from 39.5 +/- 29.4 pg/ml to 15.8 +/- 11.0 pg/ ml; p < 0.01), whereas the plasma levels of ANP did not change. We conclude that the plasma levels of BNP are increased in the majority of patients with unstable angina and that the increased levels decrease toward normal after treatment.

Neutral endopeptidase 24.11 in neutrophils modulates protective effects of natriuretic peptides against neutrophils-induced endothelial cytotoxity

This study was performed to determine effects of atrial and brain natriuretic peptides (ANP, BNP) on neutrophils-induced endothelial injury which is known to play a role in the pathophysiology of ischemia/reperfusion myocardial injury and to examine whether the effects of ANP and BNP on neutrophils are modulated by neutral endopeptidase 24.11 (NEP) in neutrophils themselves. The incubation of human neutrophils with ANP and BNP inhibited the neutrophils-induced detachment of cultured human endothelial cells (HEC). The inhibitory effect of ANP and BNP was associated with the suppressions of the neutrophils adhesiveness to HEC, CD18 expression on the neutrophils and elastase release from the neutrophils. Coincubation with UK73967 or phosphoramidon, inhibitors of NEP, potentiated all of the effects of ANP and BNP on the neutrophil functions, and the NEP inhibitors protected degradation of ANP and BNP by the neutrophils. NEP enzymatic activity in the particulate fractions and immunoreactive NEP expression were found to increase in the neutrophils from patients with early phase of acute myocardial infarction (AMI) by 5.2- and by 4.2-fold of the neutrophils from patients with late phase of AMI, respectively. In an in vivo canine model of myocardial ischemia/reperfusion, the intravenous administration of UK73967 suppressed the neutrophil adherence to endothelium and the neutrophil accumulation in the ischemic/reperfused myocardium. The results indicate that ANP and BNP, which are known to increase in AMI, modulate the neutrophil functions and exert protective effects against the neutrophils-induced endothelial cytotoxity. But the effects are suppressed due to their degradation by the neutrophil own NEP. Thus, neutrophil NEP, which also increases in AMI, may play a role in the pathophysiology of neutrophils-mediated ischemia/reperfusion endothelial and myocardial injury.

Heart period variability in patients with variant angina

To clarify how cardiac autonomic control is affected in variant angina, we analyzed heart period variability in 35 patients with variant angina and in 19 control subjects. Patients with variant angina were divided into 1-vessel (group S, n = 17) and multivessel spasm groups (group M, n = 18) according to the site(s) of ST elevation on the electrocardiogram during attacks. The 24-hour Holter electrocardiogram recorded 6 +/- 3 days after the treatment with calcium antagonist was analyzed to avoid the possible influence of spontaneous attacks. In 5 group M patients, the electrocardiogram recorded 1 month after the treatment was also analyzed. There was no difference in the number of spontaneous attacks between groups S and M. The standard deviation of all normal RR intervals (SDNN) and the percentage of differences between adjacent normal RR intervals >50 (pNN50) in variant angina were slightly but significantly lower than those in controls. There were no differences in other indexes between variant angina and controls. When the data were analyzed separately in groups S and M, averaged RR intervals (MN), SDNN, pNN50, high-frequency power, and low-frequency power in group M were significantly lower than those in group S and controls, and the ratio of low- to high-frequency power in group M was significantly higher than that in group S and controls. There was no difference in any index between group S and controls. All abnormal indexes in group M recovered to levels similar to those in controls 1 month after the treatment. In conclusion, depressed cardiac vagal control and sympathetic-dominant sympathovagal interaction were present in patients with variant angina, especially in those with multivessel spasm.

Diffuse disorder of coronary artery vasomotility in patients with coronary spastic angina. Hyperreactivity to the constrictor effects of acetylcholine and the dilator effects of nitroglycerin

OBJECTIVES

We examined the vasomotility of the entire epicardial coronary artery system in patients with and without coronary spastic angina.

BACKGROUND

The coronary arteries of patients with variant angina are hyperreactive to diverse constrictor stimuli. It is unclear whether the abnormal responses to constrictive or dilative stimuli, or both, result from a localized or diffuse disorder in the coronary artery tree.

METHODS

Coronary artery diameter responses to intracoronary acetylcholine and nitroglycerin were examined at the proximal, middle and distal segments of three principal coronary arteries in 36 patients with coronary spastic angina without significant stenosis and in 12 young (< or = 30 years old) and 20 older control subjects (> 30 years old) with normal coronary arteriographic findings. In 10 patients with significant coronary stenosis, the responses of the prestenotic segments were also examined.

RESULTS

In patients with coronary spastic angina, coronary spasm was induced in 23 left anterior descending, 13 left circumflex and 17 right coronary arteries by acetylcholine. Multivessel spasm was observed in 15 patients. Acetylcholine had a dilator effect on most segments in young control subjects and a mild constrictor effect in older control subjects and in patients with significant stenosis. Comparison of the responses to acetylcholine among groups demonstrated that the constrictor response of the artery with spasm was enhanced significantly and diffusely. That of the artery without spasm also tended to be enhanced. Coronary artery diameters after nitroglycerin did not differ in any segment among patients with coronary spastic angina and both control groups. In patients with coronary spastic angina, nitroglycerin significantly enhanced dilation in all segments of the artery with spasm compared with that observed in both control groups and in most segments of the artery without spasm. Patients with significant coronary stenosis had a reduced response compared with that in control subjects.

CONCLUSIONS

Hyperreactive responses not only to the constrictor effects of acetylcholine, but also the dilator effects of nitroglycerin were detected diffusely in the epicardial coronary arteries of patients with coronary spastic angina. This finding indicates that a diffuse, not localized, disorder in vasomotility is involved in the pathogenesis of coronary spastic angina.

Interactions of nitrovasodilators, atrial natriuretic peptide and endothelium-derived nitric oxide

Nitroglycerin (NTG), endothelium-derived relaxing factor (EDRF) and atrial natriuretic peptide (ANP) dilate vessels by a common pathway (cyclic guanosine monophosphate- dependent mechanism). Thus, these vasodilators may potentially influence the vasodilator properties of each other. We examined whether tolerance to NTG influences vasorelaxation to ANP, EDRF and other nitrovasodilators, isosorbide dinitrate (ISDN) and sodium nitroprusside (SNP). Concentration-response curves for various vasodilators during stable contraction to PGF2alpha were examined before and after the induction of NTG tolerance. Rings exposed to NTG (100 microM) for 60 min showed marked impairment of vasorelaxation to NTG itself. This NTG tolerance significantly attenuated vasorelaxation to either ISDN, SNP or EDRF stimulated by bradykinin. In contrast, the NTG tolerance did not alter vasorelaxation to either ANP or isoproterenol. The attenuated responses to NTG, ISDN, SNP and bradykinin recovered in a time-dependent manner during the subsequent washout period, suggesting this inhibition is reversible. The denudation of the endothelium significantly sensitized relaxation to NTG but did not change relaxation to ANP. These results suggest that (1) vasorelaxations to nitrovasodilators and EDRF are significantly attenuated by NTG tolerance and (2) ANP-induced vasorelaxation is not affected by exposure to either exogenous nitrovasodilator or endogenous endothelium-derived nitric oxide. ANP may be a potentially beneficial vasodilator in arteries which have developed tolerance to nitrovasodilators.

Increased constrictor response to acetylcholine of the isolated coronary arteries from patients with variant angina

The aim of this study was to determine whether isolated coronary arteries from patients with variant angina show hyperreactivity and/or supersensitivity to acetylcholine in vitro. Coronary arterial rings were obtained at autopsy within 3 h after death from six coronary arteries having spasm in four patients with variant angina and from 22 coronary arteries in 14 control patients with non-cardiac death. The coronary rings were suspended in the organ chamber filled with Krebs Henseleit solution bubbled with 95% O2 + 5% CO2, and their isometric tensions were monitored. Arterial rings isolated from both the patients with variant angina and the controls contracted dose-dependently in response to acetylcholine (10(-9)-10(-5) mol/l). EC50 of acetylcholine (i.e. concentration producing 50% of maximum contraction) was not significantly different between the coronary arteries from patients with variant angina and those from controls, but maximum contraction elicited by acetylcholine (expressed as a percentage of the contraction elicited by 60 mmol/l KCl) was significantly greater in the coronary arteries from patients with variant angina than those from controls. In conclusion, the isolated coronary arteries from patients with variant angina have hypercontractile reactivity to acetylcholine. This intrinsic alteration of the coronary reactivity to acetylcholine may play a role in the genesis of coronary spasm occurring in the situations of enhanced parasympathetic nervous discharge.

Lipoproteins regulate C-type natriuretic peptide secretion from cultured vascular endothelial cells

We have shown that oxidized low-density lipoprotein (Ox-LDL) modulates various endothelial cell (EC) functions. C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family to be discovered, is secreted from peripheral vascular ECs and regulates body fluid homeostasis, vascular tone, and vascular growth. This study was designed to investigate the effects of lipoproteins on CNP secretion from cultured ECs. Treatment of bovine carotid ECs with OX-LDL and its extracted lipids resulted in a concentration-dependent suppression of the spontaneous and transforming growth factor-beta 1-stimulated secretion CNP. Native LDL, its extracted lipids, and acetylated LDL were inactive. OX-LDL depleted of its amphiphilic lipids, which was prepared by incubation with defatted albumin, lost its suppressive effect on CNP secretion. 7-Ketocholesterol, one of the amphiphilic lipids in OX-LDL that is transferable from OX-LDL to defatted albumin, suppressed CNP secretion by ECs, thus mimicking the effect of OX-LDL. Coincubation with high-density lipoprotein (HDL), which alone had no effect on CNP release, significantly prevented OX-LDL-induced inhibition of CNP secretion by ECs. Analysis by thin-layer chromatography demonstrated that oxysterols, including 7-ketocholesterol, in OX-LDL were transferred from OX-LDL to HDL during coincubation of these two lipoproteins. These results indicate that OX-LDL suppresses CNP secretion from ECs by 7-ketocholesterol or other transferable hydrophilic lipids in OX-LDL, and the suppressive effect of OX-LDL is reversed by HDL. Lipoproteins thus may regulate CNP secretion from the endothelium of atherosclerotic arteries.

A histochemical and electron microscopic study of skeletal and cardiac muscle from a Fabry disease patient and carrier

Histochemical and electron microscopic studies were performed in an attempt to clarify the muscle pathology in an 18-year-old man with Fabry disease, showing proximal limb muscle atrophy, and his 52-year-old mother, who is a Fabry carrier with hypertrophic cardiomyopathy. Despite the relatively mild myopathic changes revealed by histochemistry, electron microscopy demonstrated the widespread accumulation of abundant lamellated bodies in myofibers, associated with increased glycogen granules and autophagic vacuoles. The cardiac muscle of the proband's mother revealed a mosaic pattern of normal-appearing and hypertrophic myofibers containing a number of ring-like, lamellated bodies. Although further studies are necessary to support our findings, skeletal muscle is apparently involved in patients with Fabry disease, and a mosaic pattern of cardiac muscle involvement possibly reflecting Lyonization, may be one of the characteristic findings of a Fabry disease carrier.

Comparison of secretion pattern between A-type and B-type natriuretic peptides in patients with old myocardial infarction

OBJECTIVES

The present study was designed to compare the secretion patterns of two cardiac hormones--A-type (atrial) and B-type (brain) natriuretic peptides--from the ventricles in patients with old myocardial infarction.

BACKGROUND

Plasma levels of these two natriuretic peptides are increased, and their secretion from the ventricles is augmented, in patients with congestive heart failure.

METHODS

We measured the plasma levels of these two types of natriuretic peptides at the aortic root and the anterior interventricular vein in 42 patients with old myocardial infarction (anterior in 22 and inferior in 20) and 18 control subjects.

RESULTS

The difference between the plasma levels of both A- and B-type natriuretic peptide in the anterior interventricular vein and aortic root was significantly greater in the groups with anterior and inferior infarction than in the control group (A-type [mean +/- SD] 380 +/- 290 and 247 +/- 205 pg/ml in the infarction groups vs. 11 +/- 14 pg/ml; B-type 497 +/- 445 and 75 +/- 73 pg/ml vs. 23 +/- 16 pg/ml, respectively). The difference between the plasma levels of each peptide at the anterior interventricular vein and aortic root had a significant negative linear correlation with left ventricular ejection fraction in both groups with infarction. The slope of the regression line of the arteriovenous difference of B-type natriuretic peptide at the anterior interventricular vein was significantly steeper in the anterior than in the inferior infarction group (left ventricular ejection fraction -12.801 vs. -1.891, p < 0.01).

CONCLUSIONS

These results indicate that 1) the secretion of A- and B-type natriuretic peptide from the left ventricular increases in proportion to the severity of left ventricular dysfunction, and 2) secretion of B-type natriuretic peptide is much greater from the infarct than from the noninfarct region, suggesting that the regional ventricular wall stretch caused by infarction strongly stimulates secretion of B-type natriuretic peptide.

Effects of brain (B-type) natriuretic peptide on coronary artery diameter and coronary hemodynamic variables in humans: comparison with effects on systemic hemodynamic variables

OBJECTIVES

This study attempted to clarify the effects of human brain (B-type) natriuretic peptide on coronary artery diameter and coronary vascular resistance in humans.

BACKGROUND

Brain natriuretic peptide induces vasodilation in systemic circulation by activating particulate guanylate cyclase of the vascular smooth muscle.

METHODS

In 13 patients with normal coronary arteries and left ventricular function, brain natriuretic peptide was infused at 0.5 microgram/kg body weight per min for 4 min into the left main coronary artery (six patients, Group A) or into the pulmonary artery (seven patients, Group B). Systemic hemodynamic variables and coronary sinus blood flow were measured before and after the infusion. The lumen diameter of the left coronary artery was quantitatively measured.

RESULTS

In both groups, brain natriuretic peptide significantly increased heart rate and decreased mean arterial pressure. Rate-pressure product remained unchanged in both groups. Brain natriuretic peptide decreased systemic vascular resistance index significantly in both groups (both p < 0.01 vs. baseline), and there was no difference in the effect between the groups. Brain natriuretic peptide decreased coronary vascular resistance in Group A (p < 0.01 vs. baseline) but did not affect coronary vascular resistance in Group B (p < 0.01 vs. Group A). The lumen diameters of the proximal and distal segments of the left coronary artery were increased significantly after brain natriuretic peptide in both groups. After infusion of brain natriuretic peptide, mean plasma level of brain natriuretic peptide in the coronary sinus increased from 36 to 130,411 pg/ml in Group A and from 64 to 12,329 pg/ml in Group B.

CONCLUSIONS

Brain natriuretic peptide shows a vasodilator effect on the coronary artery system in humans. However, the effect does not appear uniformly but is seen preferentially in the epicardial coronary artery. The sensitivity of the coronary resistance vessels to brain natriuretic peptide is low compared with that of the resistance vessels of the systemic circulation.

LPC in oxidized LDL elicits vasocontraction and inhibits endothelium- dependent relaxation

Oxidized low-density lipoprotein (ox-LDL) plays an important role in the development of atherosclerosis and potentially influences the endothelial regulation of vasomotor tone. We have recently shown that lysophosphatidylcholine (LPC), a lysophospholipid contained in ox-LDL, has various pathophysiological effects. We further examined the role of LPC in the ox-LDL-induced vasoactivity in isolated pig coronary arteries. Copper-induced ox-LDL but not native LDL (n-LDL) elicited endothelium-dependent contraction during plateau contraction evoked by prostaglandin F2 alpha. Lipid extracted from ox-LDL (ox-LDL-lipid) also induced vasocontraction, but lipid of n-LDL (n-LDL-lipid) did not influence tone. When LPC was depleted from ox-LDL (i.e., defatted albumin- or phospholipase B-treated ox-LDL), vasocontraction was significantly attenuated. Synthetic palmitoyl LPC also induced endothelium-dependent vasocontraction, mimicking the response elicited by ox-LDL, but phosphatidylcholine, which exists in n-LDL and is converted to LPC during oxidative modification of LDL, did not influence the tone. Contraction to either ox-LDL or LPC was significantly attenuated by NG-monomethyl-L-arginine but not by indomethacin or superoxide dismutase. Forty minutes of incubation of coronary rings with either ox-LDL or LPC significantly attenuated endothelium-dependent vasorelaxation to thrombin without affecting vasorelaxation to endothelium-independent vasodilator nitroglycerin. In conclusion, LPC contained in lipid fraction of ox-LDL caused endothelium-dependent contraction and inhibited endothelium-dependent relaxation in isolated pig coronary arteries. The vasocontraction might be at least in part caused by LPC-mediated inhibition of endothelium-derived nitric oxide release.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization and mechanism of secretion of B-type natriuretic peptide in comparison with those of A-type natriuretic peptide in normal subjects and patients with heart failure

BACKGROUND

B-type or brain natriuretic peptide (BNP) is a novel natriuretic peptide secreted from the heart that forms a peptide family with A-type or atrial natriuretic peptide (ANP), and its plasma level has been shown to be increased in patients with congestive heart failure. This study was designed to examine the sources and mechanisms of the secretion of BNP in comparison with those of ANP in control subjects and in patients with heart failure.

METHODS AND RESULTS

We measured the plasma levels of BNP as well as ANP in 16 patients with dilated cardiomyopathy (11 men and 5 women; mean age, 59 years) and 18 control subjects (9 men and 9 women; mean age, 54 years) by sampling blood from the femoral vein, the aortic root, the anterior interventricular vein (AIV), and the coronary sinus using the newly developed immunoradiometric assay systems. In the control subjects, there was no significant difference in the plasma ANP level between the aortic root and the AIV (24.0 +/- 5.2 pg/mL versus 32.2 +/- 17.0 pg/mL), but there was a highly significant step-up of the level between the AIV and the coronary sinus (32.2 +/- 17.0 pg/mL versus 371.4 +/- 111.1 pg/mL, P < .001). In contrast, there was a significant step-up of the plasma BNP level between the aortic root and the AIV (8.6 +/- 6.4 pg/mL versus 19.0 +/- 11.5 pg/mL, P < .01) but not between the AIV and the coronary sinus (19.0 +/- 11.5 pg/mL versus 28.8 +/- 14.0 pg/mL). On the other hand, in patients with dilated cardiomyopathy, there was a significant step-up in the plasma ANP level between the aortic root and the AIV (280.6 +/- 183.7 pg/mL versus 612.3 +/- 431.6 pg/mL, P < .01) and between the AIV and the coronary sinus (612.3 +/- 431.6 pg/mL versus 1229.0 +/- 772.7 pg/mL, P < .01). There was a significant step-up in the plasma BNP level between the aortic root and the AIV (268.4 +/- 293.2 pg/mL versus 511.6 +/- 458.1 pg/mL, P < .01) but not between the AIV and the coronary sinus (511.6 +/- 458.1 pg/mL versus 529.7 +/- 455.3 pg/mL) in patients with dilated cardiomyopathy. The arteriovenous difference at the AIV of the plasma level of BNP had a significant positive correlation with left ventricular end-systolic volume index (r = 0.859, P < .001) and a significant negative correlation with left ventricular ejection fraction (r = -.735, P < .001).

CONCLUSIONS

We conclude that (1) BNP is secreted mainly from the left ventricle in normal adult humans as well as in patients with left ventricular dysfunction, whereas ANP is secreted from atria in normal adult humans and also from the left ventricle in patients with left ventricular dysfunction; (2) secretion of BNP as well as ANP from the left ventricle increases in proportion to the severity of the left ventricular dysfunction, suggesting that the secretions of ANP and BNP from the left ventricle are regulated mainly by wall tension of the left ventricle; and (3) the peripheral plasma levels of ANP and BNP reflect the secretion rate of these hormones from the left ventricle and may be used as a marker of the degree of left ventricular dysfunction in patients with left ventricular dysfunction.

Comparison of the distribution of myocardial blood flow between exercise-induced and hyperventilation-induced attacks of coronary spasm: a study with thallium-201 myocardial scintigraphy

Exercise and hyperventilation tests are often used as the provocative tests for coronary artery spasm. To examine the distribution of myocardial blood flow during exercise-induced and hyperventilation-induced attacks of coronary spasm, thallium-201 myocardial scintigraphy was performed in 47 patients with variant angina. The extent and severity scores and severity index (severity score/extent score) of scintigraphic perfusion defect were calculated. In 32 patients, anginal attack associated with ST elevation on the electrocardiogram was induced by exercise; in 23 patients, the attack was induced by hyperventilation. In patients with either anterior or inferior wall ischemia, both the extent and severity scores and severity index in the scintigram were significantly greater in exercise-induced anginal attack than those in hyperventilation-induced attack. In patients with simultaneous anterior and inferior wall ischemia, they tended to be greater in exercise-induced attack. In eight patients in whom anginal attack was induced by both exercise and hyperventilation, these scores and index were significantly greater in exercise-induced attack than those in hyperventilation-induced attack. These data suggest that myocardial ischemia during exercise-induced attack is enhanced as compared with that during hyperventilation-induced attack. Thallium-201 scintigraphy combined with exercise testing seems to be more sensitive for detecting myocardial ischemia induced by coronary spasm.

Influence of exercise-induced coronary artery spasm on thallium-201 initial distribution and washout kinetics in patients with variant and classic angina pectoris

Thallium-201 single-photon emission computed tomography was performed immediately, and 2 and 4 hours after exercise-induced anginal attack in 2 groups of patients with either exercise-induced coronary spasm or severe fixed stenosis on the isolated proximal left anterior descending coronary artery. All patients with variant angina had transient ST-segment elevation during the exercise-induced attack for thallium-201 scintigraphic study. Both perfusion defects and 4-hour washout abnormalities were significantly greater in patients with variant angina than in those with stable effort angina (p < 0.01). In patients with stable effort angina, thallium-201 activity in ischemic regions (as a percentage of initial count in the normal region) progressively decreased, whereas in patients with variant angina it increased from 38% (initial) to 48% (2 hours), and then declined to 42% (4 hours). The initial normalized thallium-201 activity in the ischemic regions was significantly lower in patients with variant angina than in those with stable effort angina (p < 0.001). In conclusion, perfusion and washout abnormalities during exercise-induced angina are greater in patients with variant angina than in those with stable effort angina. Exercise-induced coronary spasm seems to contribute to the profound reduction in initial thallium-201 distribution and delayed thallium-201 accumulation in the ischemic region.

Lysophosphatidylcholine in oxidized low-density lipoprotein increases endothelial susceptibility to polymorphonuclear leukocyte-induced endothelial dysfunction in porcine coronary arteries. Role of protein kinase C

We have shown that transferred lysophosphatidylcholine (lysoPC) from oxidized low-density lipoprotein (Ox-LDL) to endothelial surface membrane activates protein kinase C (PKC) in endothelial cells, suggesting that Ox-LDL could alter endothelial functions through PKC activation. The purposes of the present study were to examine whether the endothelial susceptibility to polymorphonuclear leukocytes (PMNs) may be altered in Ox-LDL-treated coronary arteries, which have properties closely resembling those observed in atherosclerotic arteries, and to determine the mechanism(s) by which Ox-LDL may affect the endothelial susceptibility to PMNs. Isolated porcine coronary arteries were cannulated and perfused with oxygenated culture medium with or without LDLs or lipids at a constant flow (37 degrees C, pH 7.4). The treatment of porcine coronary arteries with Ox-LDL increased endothelial adhesiveness to PMNs and augmented PMN-induced impairment of endothelium-dependent arterial relaxation (EDR). Furthermore, Ox-LDL stimulated the expression of intercellular adhesion molecule-1 (ICAM-1) in the porcine coronary arterial endothelium. These effects of Ox-LDL were not mediated by the scavenger-receptor-mediated process but were attributed to lysoPC in Ox-LDL. Blocking of the PMN adherence to endothelium by using anti-CD18 monoclonal antibody abolished the PMN-induced impairment of EDR. Coincubation with staurosporine or calphostin C, inhibitors of PKC, during treatment of the arteries with Ox-LDL or lysoPC attenuated the augmentative effects of Ox-LDL and lysoPC on endothelial ICAM-1 expression, endothelial adhesiveness to PMNs, and PMN-induced EDR impairment. Treatment of the arteries with phorbol 12-myristate 13-acetate, a potent stimulator of PKC, induced ICAM-1 expression and enhanced the endothelial adhesiveness to PMNs and PMN-induced EDR impairment, mimicking the effects of Ox-LDL. These results suggest that lysoPC in Ox-LDL induces endothelial ICAM-1 expression, which facilitates PMN adherence to endothelium and the subsequent augmentation of PMN-induced EDR impairment. PKC activation in endothelial cells by lysoPC in Ox-LDL may at least in part be involved in these effects of Ox-LDL. LysoPC in Ox-LDL increases endothelial susceptibility to PMN-induced endothelial dysfunction.

Cigarette smoke extract contracts isolated porcine coronary arteries by superoxide anion-mediated degradation of EDRF

To test whether cigarette smoke extract (CSE) influences the endothelial regulation of vascular tone in vitro, pig coronary arterial rings were incubated in organ chambers and isometric tension changes were examined. CSE was prepared by bubbling mainstream smoke of one filter cigarette into phosphate-buffered saline (2 ml). Fresh CSE (3.3, 10, and 30 microliters/ml) elicited initial contraction and subsequent relaxation during stable contraction to prostaglandin F2 alpha (PGF2 alpha). Initial contraction to CSE was dependent on the presence of endothelium, whereas subsequent relaxation was endothelium independent. Initial contraction was significantly attenuated by superoxide dismutase (SOD), methylene blue, but not by catalase. Prior inhibition of the basal release of endothelium-derived relaxing factor by NG-monomethyl-L-arginine also inhibited the initial contraction, and this inhibition was reversed by coincubation with L-arginine but not D-arginine. Subsequent relaxation was significantly potentiated by SOD but was markedly attenuated by methylene blue. CSE reduced ferricytochrome c, and this reduction was significantly inhibited by SOD. In conclusion, CSE induced biphasic tension change, initial contraction, and subsequent relaxation during stable contraction to PGF2 alpha in isolated pig coronary arteries. The initial contraction may be, at least in part, mediated through the degradation of basally released endothelium-derived relaxing factor (nitric oxide) by superoxide anions derived from CSE.

Protein kinase C inhibitors prevent impairment of endothelium-dependent relaxation by oxidatively modified LDL

The mechanism(s) of inhibition of endothelium-dependent relaxation (EDR) by oxidized low-density lipoprotein (Ox-LDL) was examined in isolated porcine coronary arteries and rabbit aortas. Incubation with Ox-LDL but not native LDL caused the inhibition of thrombin- or acetylcholine-induced EDR, whereas A23187-induced EDR was preserved after incubation with Ox-LDL. Lysophosphatidylcholine (lysoPC), which was abundant in Ox-LDL and was found to be transferred from Ox-LDL to endothelial cells, also caused the inhibition of EDR in response to thrombin or acetylcholine but not to A23187. Ox-LDL depleted of lysoPC, which was prepared by phospholipase B, failed to inhibit the vasorelaxation. Coincubation with staurosporine or calphostin C, potent inhibitors of protein kinase C, attenuated the EDR inhibition by Ox-LDL or lysoPC. Phorbol 12-myristate 13-acetate, a specific protein kinase C activator, caused the EDR inhibition, and its effect was attenuated by staurosporine or calphostin C. Furthermore, lysoPC was capable of activating protein kinase C purified from cultured porcine endothelial cells. In conclusion, protein kinase C activation plays a role in the inhibition of surface receptor-mediated EDR by Ox-LDL, and lysoPC transferred from Ox-LDL to endothelial cells may be involved in the activation of protein kinase C.

Transferable lipids in oxidized low-density lipoprotein stimulate plasminogen activator inhibitor-1 and inhibit tissue-type plasminogen activator release from endothelial cells

Decreased fibrinolytic activity has been reported in atherosclerotic cardiovascular diseases. To determine whether oxidized low-density lipoprotein (Ox-LDL), which accumulates in atherosclerotic arteries, modulates the endothelial fibrinolytic system, cultures of human umbilical vein endothelial cells were incubated with low-density lipoproteins or lipids, and levels of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) antigens in the conditioned medium were measured by enzyme-linked immunosorbent assay. Ox-LDL (30 micrograms protein/mL) and its extracted lipid (50 micrograms cholesterol/mL) stimulated PAI-1 release by 42 +/- 3% and 29 +/- 3% of control cultures, respectively, whereas Ox-LDL and its lipid inhibited t-PA release by 42 +/- 4% and 53 +/- 3% of control cultures, respectively. Native LDL and its lipid were inactive on their release. Ox-LDL depleted of hydrophilic lipids, which was prepared by the incubation with defatted albumin (an acceptor for hydrophilic lipids), lost both the stimulatory action on PAI-1 and the inhibitory action on t-PA. The extracted lipid from the incubated albumin, which has been found to accept the hydrophilic lipids from Ox-LDL, gained the stimulatory action on PAI-1 and the inhibitory action on t-PA. Ox-LDL depleted of lysophosphatidylcholine (LPC), which was prepared by the incubation with phospholipase B, lost the stimulatory effect on PAI-1, whereas the inhibitory effect on t-PA remained present in the Ox-LDL depleted of LPC. The incubation with synthetic palmitoyl LPC (10 microM) stimulated PAI-1 release by 85 +/- 7% of control.(ABSTRACT TRUNCATED AT 250 WORDS)

Activated human polymorphonuclear leukocytes elicit endothelium-dependent contraction in isolated pig coronary arteries

Interaction between activated human polymorphonuclear leukocytes (PMNL) and endothelial regulation of isolated pig coronary artery tone was examined. PMNL were isolated from venous blood of healthy human volunteers. Pig coronary artery rings were incubated in an organ chamber, and isometric tension changes induced by opsonized zymosan (1 mg/ml)-activated PMNL were examined. Activated PMNL elicited dose-dependent contraction (maximum value 45.9 +/- 4.1% of precontraction, mean +/- SEM] in prostaglandin F2 alpha (PGF2 alpha)-precontracted rings. The contraction was markedly attenuated by superoxide dismutase (SOD 100 U/ml) to 9.9 +/- 2.4% (p < 0.001), but not by catalase (1,000 U/ml). After inhibition of basal production of endothelium-derived relaxing factor (EDRF) (nitric oxide, NO) by endothelial removal or by treatment of an inhibitor of NO synthase, NG-monomethyl-L-arginine (L-NMMA), PMNL also failed to induce the contraction. A 5-lipoxygenase inhibitor (AA-861) and a cyclooxygenase inhibitor (indomethacin) did not alter the contraction to activated PMNL significantly. Time course of oxygen free radical release from PMNL measured by luminol-dependent chemiluminescence was closely synchronized with that of the endothelium-dependent contraction elicited by PMNL. In each preparation of PMNL, the maximum luminescence count and the maximum contraction induced by activated PMNL showed significant positive correlation quantitatively (r = 0.958, p < 0.001). Activated human PMNL elicited endothelium-dependent contraction in isolated pig coronary arteries. The contraction may be mediated through inactivation of basal production of EDRF (NO) by superoxide anions released from PMNL.

Contraction and endothelium dependent relaxation via alpha adrenoceptors are variable in various pig arteries

OBJECTIVE

The aim was to examine differences in the vascular response to alpha adrenoceptor stimulation on both smooth muscle and endothelium among large arteries perfusing various organs.

METHODS

In ring preparations of coronary, carotid, iliac, mesenteric, and renal arteries from pigs (n = 24), the magnitudes of contraction to noradrenaline (with beta blocker), with or without endothelium, and endothelium dependent relaxation to noradrenaline (with alpha 1 and beta blocker) were compared in vitro.

RESULTS

In both endothelium-intact and denuded groups, the contractions to noradrenaline were significantly smaller in coronary and carotid arteries than in iliac, mesenteric, and renal arteries. The presence of endothelium significantly suppressed the contractions in coronary and carotid arteries, but did not affect the contractions in iliac, mesenteric, and renal arteries. The endothelium dependent relaxations to noradrenaline, which were abolished by LNMMA, were more prominent in coronary and carotid arteries than in iliac, mesenteric, and renal arteries.

CONCLUSIONS

The contractions via alpha adrenoceptors were small, and endothelium dependent relaxations via alpha 2 adrenoceptors were large, in the coronary and carotid arteries, which perfuse the vital organs (heart and brain), as compared with those in iliac, mesenteric, and renal arteries. These results suggest that in the state of activation of the sympathetic nervous system, arterial tone in response to alpha adrenoceptor stimulation may be regulated not only by alpha adrenoceptors on vascular smooth muscle but also by those on endothelium, through release of endothelium derived relaxing factor (EDRF) via alpha 2 adrenoceptors.

Effects of lysolipids and oxidatively modified low density lipoprotein on endothelium-dependent relaxation of rabbit aorta

Exposure of isolated arteries to oxidatively modified low density lipoprotein (LDL) has been reported to suppress endothelium-dependent relaxation (EDR). To determine whether lipid degradation products in oxidized LDL contribute to impaired relaxation, we have tested the responsiveness of isolated rabbit aortas to endothelium-dependent relaxants (acetylcholine, ATP, and calcium ionophore A23187) and nitroglycerin before and after 2-hour incubations with selected lipids and LDL preparations. Concentrations (10 microM) of lecithin, phosphatidylserine, lysophosphatidylserine, sphingomyelin, phosphatidic acid, palmitate, arachidonate, and auto-oxidized arachidonate had no effect on EDR. Concentrations (10 microM) of lysolecithin, lyso-platelet activating factor, and sphingosine significantly suppressed endothelium-dependent relaxation. Native LDL (100 micrograms/ml incubation buffer) containing only small amounts of lysophosphatidylcholine exerted no effect on EDR. In contrast, LDL preparations oxidatively modified by exposure to cultured endothelial cells or copper inhibited EDR. When modified LDL was depleted of its lysolecithin by treatment with a selective phospholipase B (lysolecithinase), the inhibitory effects were attenuated. In contrast, native LDL accumulating lysolecithin under the influence of a phospholipase A2 (lecithinase) exerted inhibitory effects mimicking those of oxidized LDL. Lipids and lipoproteins had no effect on the responsiveness to nitroglycerin, an endothelium-independent vasodilator. We conclude that lysolecithin in oxidatively modified LDL contributes importantly to its vasomotor effects.

Lysophosphatidylcholine inhibits surface receptor-mediated intracellular signals in endothelial cells by a pathway involving protein kinase C activation

Lysophosphatidylcholine (lysoPC) transferred from oxidatively modified low density lipoprotein (Ox-LDL) to the endothelial surface membrane has been shown to produce a selective unresponsiveness to cell surface receptor-regulated endothelium-dependent relaxation (EDR) in the rabbit aorta. To determine its mechanism we examined the effects of lysoPC on endothelial surface receptor-mediated transmembrane signals. Incubation for 1 minute with palmitoyl lysoPC (5-10 microM) decreased thrombin (Th, 2 units/ml)- or histamine (His, 0.1 mM)-stimulated inositol 1,4,5-trisphosphate (IP3) production in primary cultures of human umbilical vein endothelial cells (HUVECs). LysoPC also decreased Th- or His-induced intracellular calcium ([Ca2+]i, fura 2) elevation. Pretreatment with protein kinase C (PKC) inhibitors staurosporine (100 nM) or H-7 (50 microM) prevented the inhibitory actions of lysoPC, but HA-1004 had no effect. Incubation for 5 minutes with phorbol 12-myristate 13-acetate (PMA, 100 nM) produced the inhibitory actions on the Th- or His-induced intracellular signals, which closely mimic those exhibited by lysoPC. However, the inhibitory effect of lysoPC was lost in cells that were depleted of PKC by pretreatment for 24 hours with 100 nM PMA. Furthermore, incubation of the cells for 1 minute with lysoPC stimulated PKC activity in the membrane fraction. In organ chamber experiments with porcine coronary artery rings, pretreatment with staurosporine (20 nM) attenuated lysoPC-induced impairment of EDR in response to Th. These results indicate that lysoPC, which accumulates in Ox-LDL and atherosclerotic arterial walls, inhibits the early transmembrane signaling pathway in endothelial cells, and PKC activation could at least partially be involved in the negative regulation by lysoPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of endothelin-1 secretion by lysophosphatidylcholine in oxidized low density lipoprotein in cultured vascular endothelial cells

Oxidatively modified low density lipoprotein (oxidized LDL), an atherogenic lipoprotein that exists in the atherosclerotic arteries, has been shown to alter endothelial cell functions. In the present study, we examined the effects of oxidized LDL on the production of endothelin-1-like immunoreactivity (ET-1-LI) by the cultured vascular endothelial cells from porcine aorta and human umbilical vein. Incubation with oxidized LDL resulted in a dose-dependent suppression of ET-1-LI release by both endothelial cells. Oxidized LDL also inhibited thrombin-mediated stimulation of ET-1-LI secretion. However, native LDL had no effects on ET-1-LI secretion. A lipid extract from oxidized LDL, but not from native LDL, inhibited ET-1-LI secretion, indicating that the lipid component of oxidized LDL was required for the inhibition of ET-1-LI secretion. Oxidative modification of LDL was associated with degradation of a substantial amount of phosphatidylcholine to lysophosphatidylcholine (LPC). Pretreatment with defatted albumin, which is an acceptor for hydrophilic lipids including LPC, reduced LPC concentration in oxidized LDL to that in native LDL and simultaneously prevented the inhibitory effects of oxidized LDL on ET-1-LI secretion. Incubation with synthetic LPC (palmitoyl), but not with synthetic phosphatidylcholine (dipalmitoyl), suppressed ET-1-LI secretion by the endothelial cells. No cell death was observed during the incubations as judged by the trypan blue exclusion test, and protein synthesis of the endothelial cells was not affected by lipids or lipoproteins at a concentration at which suppression of ET-1-LI was observed. We concluded that LPC in oxidized LDL causes suppression of ET-1-LI release, which may counteract the vasoconstrictive properties of atherosclerotic arteries.

A study on coronary hemodynamics during acetylcholine-induced coronary spasm in patients with variant angina: endothelium-dependent dilation in the resistance vessels

The epicardial coronary artery of patients with variant angina is hyperreactive to the constrictive effect of acetylcholine, but it is not known whether the coronary microvasculature also constricts in response to acetylcholine. Incremental doses of acetylcholine were injected into the left coronary artery of 57 patients with variant angina and with spasm in this artery. By measuring coronary sinus blood flow, coronary hemodynamic status just before angiographic documentation of spasm was examined. Acetylcholine induced spasm in the left coronary artery in all patients. It also decreased the diameter of the nonspasm artery by 36 +/- 19% from baseline. For all patients, coronary sinus blood flow was 89 +/- 38 ml/min at baseline and increased to 104 +/- 61 ml/min during an acetylcholine-induced anginal attack (p less than 0.01). In 10 patients with spasm in both the left anterior descending and left circumflex arteries (that is, multivessel spasm), coronary sinus blood flow decreased from 84 +/- 21 to 52 +/- 26 ml/min (p less than 0.01). In the other 47 patients with spasm in only one of these two arteries (that is, single-vessel spasm), coronary sinus blood flow increased from 90 +/- 41 to 115 +/- 61 ml/min (p less than 0.01) without change in the rate-pressure product. It is concluded that in patients with variant angina, acetylcholine induces spasm and constriction in the epicardial coronary artery, whereas it dilates the resistance vessels presumably through the release of the endothelium-dependent relaxing factor.

Decreased perfusion in myocardial region of normal donor artery secondary to collateral development. Stress 201Tl myocardial emission CT performed in patients with single vessel exertional angina having collaterals

Thirty-one patients suffering from single vessel exertional angina with collaterals (Group A) were evaluated by stress 201T1 myocardial emission CT (Tl-SPECT) with 16 controls of severely stenotic single vessel exertional angina without collaterals (Group B). Group A included 21 patients (68%) who showed an extensive perfusion defect in double artery myocardial regions, including the normal donor artery myocardial region (DMR). However, there were no such cases in Group B, giving a significant difference between these 2 groups (p less than 0.001). Four patients in Group A, having a perfusion defect both in DMR and in the collateral dependent myocardial region (CMR) underwent a successful percutaneous transluminal coronary angioplasty (PTCA) with disappearance of collaterals. Tl-SPECT findings after PTCA showed no perfusion defect either in CMR or in DMR. This has been explained on the basis that the coronary collaterals stole blood and produced perfusion defect in DMR.

Magnesium deficiency detected by intravenous loading test in variant angina pectoris

To study whether magnesium (Mg) deficiency is present in patients with variant angina, 24-hour Mg retention of low dose Mg (0.2 mEq/kg lean body weight) administered intravenously over 4 hours in 20 patients with variant angina was examined. No patient had received calcium antagonists before or during the study. All had attacks of chest pain associated with ST elevation on electrocardiograms. Twenty-one subjects without ischemic heart disease were studied as control subjects. Ten patients with variant angina were restudied 10 to 529 days (mean 235 +/- 30) after the treatment with calcium antagonists (diltiazem 120 to 240 or nifedipine 40 to 80 mg/day), which resulted in complete suppression of anginal attacks. The mean serum Mg concentrations in the patients with variant angina and the control subjects were 2.1 +/- 0.05 and 2.1 +/- 0.03 mg/dl, respectively (difference not significant). However, 24-hour Mg retention in the patients with variant angina was 60 +/- 5%, while that in the control subjects was 36 +/- 3% (p less than 0.001), suggesting that Mg deficiency is present in at least some patients with variant angina. The mean serum Mg concentrations before and after calcium antagonist treatment in 10 patients with variant angina were 2.1 +/- 0.09 and 2.1 +/- 0.07 mg/dl, respectively (difference not significant). However, 24-hour Mg retention decreased significantly (p less than 0.01) from 60 +/- 6 to 34 +/- 7% after the treatment. There is Mg deficiency in many patients with variant angina and it is corrected after treatment with calcium antagonists.

Impairment of endothelium-dependent arterial relaxation by lysolecithin in modified low-density lipoproteins

Atherosclerosis in animals and humans is associated with an unresponsiveness of arteries and arterioles to endothelium-dependent vasodilators--agents acting on smooth muscle indirectly by stimulating the release from endothelial cells of a vasodilator principle (endothelium-derived relaxing factor). Altered vasomotor regulation in atherosclerosis could partly reflect an injurious action of abnormal lipoproteins on endothelium. Recently, 'cell-modified' or 'oxidized' low-density lipoprotein (EC-LDL) has received increasing attention because of its potential cytotoxic and atherogenic properties. We report here that arteries exposed to EC-LDL in vitro show an endothelium-dependent vasoregulatory impairment closely resembling that of atherosclerotic arteries. Our results indicate that transfer of lysolecithin from EC-LDL to endothelial membranes produces a selective unresponsiveness to receptor-regulated endothelium-dependent vasodilators.

Suppression of exercise-induced angina by magnesium sulfate in patients with variant angina

The effects of intravenous magnesium on exercise-induced angina were examined in 15 patients with variant angina and in 13 patients with stable effort angina and were compared with those of placebo. Symptom-limited bicycle exercise and thallium-201 myocardial scintigraphy were performed after intravenous administration of 0.27 mmol/kg body weight of magnesium sulfate and after placebo on different days. In all patients, serum magnesium levels after administration of magnesium sulfate were about twofold higher than levels after placebo. Exercise-induced angina associated with transient ST segment elevation occurred in 11 patients with variant angina receiving placebo and in only 2 of these patients receiving magnesium (p less than 0.005). On the other hand, exercise-induced angina was not suppressed by magnesium in any patient with stable effort angina. In these patients there was no significant difference in exercise duration after administration of placebo versus after administration of magnesium. The size of the perfusion defect as measured by thallium-201 scintigraphy was significantly less in patients with variant angina receiving magnesium than that in those receiving placebo (p less than 0.001), whereas it was not significantly different in patients with stable effort angina receiving placebo versus magnesium. In conclusion, exercise-induced angina is suppressed by intravenous magnesium in patients with variant angina but not in patients with stable effort angina. This beneficial effect of magnesium in patients with variant angina is most likely due to improvement of regional myocardial blood flow by suppression of coronary artery spasm.

Multivessel coronary spasm in patients with variant angina: a study with intracoronary injection of acetylcholine

Multivessel coronary spasm has been described but its incidence in patients with variant angina still remains unclear. Thirty-three patients with variant angina were studied during coronary angiographic examination with selective intracoronary injection of acetylcholine (ACh). In all but three patients, the location of ischemia during attack was determined by the electrocardiographic findings, by exercise 201Tl myocardial scintigraphy, and by two-dimensional echocardiography during a hyperventilation test, and the coronary artery (or arteries) responsible for the attack was predicted before the study. ACh induced spasm of at least one coronary artery in all but one patient. ACh induced spasm of both the left and right coronary arteries (i.e., multivessel coronary spasm) in 24 patients: in two of the four patients who were predicted to have spasm of the left coronary artery, in six of the 11 predicted to have spasm of the right coronary artery, in 13 of the 15 predicted to have spasm of both the left and right coronary arteries, and in three of the three in whom coronary artery responsible for attack had not been predicted. This ACh-induced spasm of the left and right coronary arteries occurred separately and no patients showed hemodynamic instability during attack. In one patient in whom multivessel coronary spasm had been predicted and ACh failed to induice coronary spasm, ergonovine maleate (0.2 mg) induced spasm of both the left and right coronary arteries simultaneously, resulting in severe prolonged hypotension. Nineteen of the 25 patients in whom multivessel coronary spasm was documented showed angiographically normal or nearly normal coronary arteries after administration of nitroglycerin.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous multivessel coronary artery spasm demonstrated by quantitative analysis of thallium-201 single photon emission computed tomography

Thallium-201 myocardial scintigraphy with quantitative analysis of emission computed tomography was performed during episodes of angina in 19 patients with variant angina and nearly normal coronary arteriographic findings. Eleven patients (group I) were shown by arteriography to have spasm in 2 or more large coronary arteries. Eight patients (group II) had spasm in only 1 coronary artery. In 7 patients in group I, significant diffuse perfusion defects simultaneously appeared in multiple coronary artery regions on the scintigram (group IA). The extent and severity of the perfusion defect as measured by thallium-201 tomography were significantly greater in group IA than in group II (p less than 0.001 and p less than 0.01, respectively). The duration of transient ST-segment elevation during the attack in group IA was significantly longer than in group II (p less than 0.001). The incidence of ventricular arrhythmias, including ventricular tachycardia, or complete atrioventricular block during the anginal attack was significantly higher (p less than 0.05) in group IA than in group II. In all study patients, neither attack nor scintigraphic perfusion defect appeared on the repeat test after oral administration of nifedipine. In conclusion, multivessel coronary artery spasm simultaneously appears and causes the attack in many patients with variant angina and nearly normal coronary arteriographic findings, and myocardial ischemia due to simultaneous multivessel coronary spasm is likely to be more extensive and severe, persist longer and have a higher frequency of potentially dangerous arrhythmias than that due to spasm of only 1 coronary artery.

Induction of coronary artery spasm by acetylcholine in patients with variant angina: possible role of the parasympathetic nervous system in the pathogenesis of coronary artery spasm

We injected acetylcholine (ACh), the neurotransmitter of the parasympathetic nervous system, into the coronary arteries of 28 patients with variant angina. Injection of 10 to 80 micrograms ACh into the coronary artery responsible for the attack induced spasm together with chest pain and ST segment elevation or depression on the electrocardiogram in 30 of the 32 arteries of the 25 of the 27 patients. The injection of 20 to 100 micrograms ACh into the coronary artery not responsible for the attack in 18 patients resulted in various degrees of constriction in most of them, but no spasm in any of them. After intravenous injection of 1.0 to 1.5 mg atropine sulfate, the injection of ACh into the coronary artery responsible for the attack did not induce spasm or attack in any of the nine coronary arteries injected in eight patients. We conclude that the intracoronary injection of ACh induces coronary spasm and attack in patients with variant angina and that the activity of the parasympathetic nervous system may play a role in the pathogenesis of coronary spasm. We also conclude that the intracoronary injection of ACh is a useful test for provocation of coronary spasm.