Role of nitric oxide in vascular tone and in reactivity to isoproterenol and adenosine in the goat coronary circulation

The present study examined the role of nitric oxide in coronary vascular tone and in the coronary vasodilatation in response to beta-adrenoceptor stimulation and adenosine. In anesthetized goats, the effects of intracoronary and i.v. administration of the inhibitor of nitric oxide synthesis, N(w)-nitro-L-arginine methyl ester (L-NAME), and those of isoproterenol, adenosine and acetylcholine on coronary blood flow, measured electromagnetically in the left circumflex coronary artery, were recorded. Intracoronary infusion of L-NAME (30-40 microg kg(-1) min(-1), four goats) reduced resting coronary blood flow by 14+/-3% (P<0.05) without changing arterial pressure and heart rate. L-NAME (40 mg kg(-1), eight goats) i.v. reduced resting coronary blood flow by 19+/-4% (P<0.05), increased mean systemic arterial pressure by 22+/-3% (P<0.01) and decreased heart rate by 10+/-2% (P<0.05). These effects of L-NAME were partially, but significantly reversed by L-arginine (six goats). Isoproterenol (10-100 ng, eight goats), adenosine (0.3-10 microg, seven goats) and acetylcholine (3-100 ng, five goats), injected intracoronarily, increased coronary conductance in a dose-dependent way and, under control conditions, these increases for isoproterenol, ranged from 32+/-5% to 82+/-12%; for adenosine, 6+/-2% to 174+/-22%; and for acetylcholine, 39+/-5% to 145+/-15%. During i.v. L-NAME the increases in coronary conductance induced by isoproterenol and acetylcholine were significantly reduced by about 50 and 60% (P<0.05), respectively, whereas those induced by adenosine were significantly increased further (about 30-100%, P<0. 05). During L-NAME plus L-arginine, the effects of isoproterenol, acetylcholine and adenosine on coronary conductance were not significantly different from those under control conditions. Therefore, it is suggested that in the coronary circulation: (a) nitric oxide may produce a basal vasodilator tone under normal conditions; (b) nitric oxide may be an intermediate in the vasodilatation due to beta-adrenoceptor stimulation and acetylcholine, and (c) the vasodilatation due to adenosine is potentiated during reduction of nitric oxide production.     

Transient improvement of acetylcholine responses after short-term oral L-arginine in forearms of human heart failure

Patients with heart failure exhibit impaired endothelium-dependent vasodilation. Although brief intraarterial administration of L-arginine improves endothelium-dependent vasodilatation in these patients, long-term oral supplementation is ineffective. To resolve these conflicting findings, we examined the effect of a single, short-term oral dose of L-arginine on serial, hourly forearm vascular responses to acetylcholine, sodium nitroprusside, and norepinephrine. Eighteen patients with heart failure were randomly allocated in a double-blinded, crossover study to receive either a single 20-g oral dose of L-arginine or placebo. Vascular responses were measured by forearm venous occlusion plethysmography before and at 60, 120, and 180 min after dosage. Blood was obtained for measurement of L-arginine and nitric oxide metabolite levels. Oral L-arginine increased plasma levels by fourfold at 60, 120, and 180 min. Vasodilatation to acetylcholine, 37 microg/min, was significantly enhanced at 60 min (percentage increase in forearm blood flow: placebo, 413 +/- 64%; L-arginine, 587 +/- 94%; p < 0.05), discernible at 120 min (p = 0.058) but no longer apparent at 180 min. Neither basal forearm blood flow, sodium nitroprusside, nor norepinephrine responses nor plasma levels of nitrite and nitrate were altered. We conclude that although short-term oral supplementation with L-arginine produced marked sustained elevation of plasma levels of L-arginine in patients with heart failure, responses to acetylcholine were only transiently improved.     

Ginkgo biloba extract improves coronary blood flow in patients with coronary artery disease: role of endothelium-dependent vasodilation

Ginkgo biloba extract (GBE) has well-documented cardioprotective effects on coronary flow and positive effects on vasodilation through endothelium-derived nitric oxide in experimental animals, but these impacts in patients with coronary artery disease (CAD) have not yet been investigated. We designed this study to test the effects of GBE on distal left anterior descending coronary artery (LAD) blood flow and endothelium-dependent brachial artery flow-mediated dilation (FMD) in patients with CAD. Eighty CAD patients were randomly assigned to either GBE or saline (control) groups. LAD blood flow and brachial artery FMD were measured non-invasively using high-resolution ultrasound before and after intravenous administration of GBE or saline. GBE significantly increased LAD blood flow in maximal diastolic peak velocity (MDPV), maximal systolic peak velocity (MSPV) and diastolic time velocity integral (DTVI) compared with the control group (16.14 +/- 10.93 % vs. 0.28 +/- 2.14 %, 9.14 +/- 8.23 % vs. 0.79 +/- 2.56 %, and 15.23 +/- 7.28 % vs. 0.42 +/- 2.43 %, respectively, p < 0.01). Brachial artery FMD was also increased by 69.75 % (from 3.95 +/- 1.49 % to 6.55 +/- 2.51 %, p < 0.01). A linear correlation was found between the percentage changes in MDPV, MSPV, or DTVI of LAD blood flow and the percentage change in brachial artery FMD following treatment with GBE (r = 0.612, 0.486, or 0.521, respectively, p < 0.01). In summary, our data demonstrate that GBE treatment in CAD patients leads to an increase of LAD blood flow in MDPV, MSPV and DTVI, and the increase response might relate to the improved endothelium-dependent vasodilatory capacity. CAD: coronary artery disease DTVI: diastolic time velocity integral FMD: flow-mediated dilation GBE: GINKGO BILOBA extract LAD: distal left anterior descending coronary artery MDPV: maximal diastolic peak velocity MSPV: maximal systolic peak velocity NO: nitric oxide TTDE: transthoracic Doppler echocardiography.     

Long-term treatment with eicosapentaenoic acid augments both nitric oxide-mediated and non-nitric oxide-mediated endothelium-dependent forearm vasodilatation in patients with coronary artery disease

Long-term treatment with eicosapentaenoic acid (EPA) is known to improve impaired endothelium-dependent relaxations of atherosclerotic blood vessels in animals and humans. However, it remains to be determined which mechanisms are involved in this beneficial effect of EPA. In this study, we investigated our hypothesis that EPA improves both nitric oxide (NO)-mediated and non-NO-mediated endothelium-dependent vasodilatation in patients with coronary artery disease. The study included eight patients with documented coronary artery disease. The forearm vascular responses to the endothelium-dependent vasodilator acetylcholine and substance P were examined before and after intraarterial infusion of NG-monomethyl-L-arginine (L-NMMA). Same measurements were repeated after the treatment with EPA (1,800 mg/day) for 6 weeks. The long-term treatment with EPA augmented forearm blood-flow response to both acetylcholine and substance P. Furthermore, acute administration of L-NMMA significantly inhibited the EPA-induced augmented response to acetylcholine but not that to substance P. The forearm vascular response to sodium nitroprusside was unchanged by the EPA treatment. These results indicate that long-term treatment with EPA augments both NO-dependent and non-NO-dependent endothelium-dependent forearm vasodilatation in patients with coronary artery disease. Thus the beneficial effects of EPA appear to extend to non-NO-dependent mechanism(s).     

Allopurinol and amlodipine improve coronary vasodilatation after myocardial ischaemia and reperfusion in anaesthetized dogs.

1. We have assessed the effect of allopurinol, amlodipine and propranolol pretreatment on both endothelium-dependent and endothelium-independent coronary vasodilatation in vivo, by comparing pre-ischaemic responses with those measured after 60 min of coronary artery occlusion and 30 min of reperfusion in anaesthetized dogs. 2. In 15 untreated dogs ischaemia and reperfusion attenuated the increases in coronary blood flow produced by either acetylcholine (0.01-0.05 micrograms kg-1, i.a.) or glyceryl trinitrate (0.05-0.2 micrograms kg-1, i.a.), to an average of 39 +/- 4% and 42 +/- 5% of the pre-ischaemic control response, respectively (both P < 0.05). 3. In 5 dogs treated with allopurinol (25 mg kg-1, orally, 24 h previously, plus 50 mg kg-1, i.v., 5 min before occlusion), the increases in coronary blood flow after ischaemia and reperfusion (acetylcholine: 78 +/- 12%, glyceryl trinitrate: 60 +/- 3% of pre-ischaemic response) were significantly larger than post-ischaemic responses in untreated dogs (both P < 0.05). 4. Similarly, amlodipine treatment (3 micrograms kg-1 min-1, i.v., starting 90 min before occlusion) in 5 dogs improved post-ischaemic increases in blood flow (acetylcholine: 58.5%, glyceryl trinitrate: 66 +/- 6% of pre-ischaemic response, significantly greater than post-ischaemic responses in untreated dogs, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic decrease in flow contributes to heart failure-induced endothelial dysfunction in rats

Chronic heart failure (CHF) impairs endothelium-dependent, nitric oxide (NO)-mediated dilation. This decreased dilation may be partly secondary to the chronic decrease in blood flow, but this hypothesis has not yet been tested. Thus, we assessed whether a localized, chronic increase in blood flow in vivo reverses endothelial dysfunction of small arteries in rats with CHF. Two months after coronary artery ligation or sham surgery, second-order side branches of the superior mesenteric artery were ligated in order to obtain persistently elevated blood flow (HF) in the adjacent first-order side branch compared with normal vessels (NF). One month later, responses to acetylcholine and flow-mediated vasodilatation (FMD) were assessed in vitro in an arteriograph. Chronic heart failure induced a decrease in mesenteric blood flow (374 +/- 25 and 305 +/- 27 micro L/min for sham and CHF, respectively; P < 0.05). Neither CHF nor the chronic increase in flow affected the responses to acetylcholine. Chronic heart failure decreased FMD (maximal response in sham and control 34 +/- 6 and 13 +/- 4%, respectively; P < 0.05). Chronic increases in blood flow did not modify FMD in sham, but restored FMD in CHF rats (28 +/- 4%; P < 0.05 vs CHF NF). The restored response was abolished by an inhibitor of NO synthesis (N(G)-nitro-l-arginine). Chronic heart failure did not affect the abundance of mesenteric endothelial NO synthase (eNOS) mRNA. A chronic increase in flow significantly increased the abundance of eNOS mRNA in sham rats, but only moderately and non-significantly in CHF rats. Thus, endothelial dysfunction of small arteries in CHF appears to be largely the consequence of the chronic decrease in flow.     

Lercanidipine对心肌病仓鼠心力衰竭过程中冠状反应和重构的作用

AIM: Lercanidipine is a new vasoselective dihydropyridine calcium channel blocker with a short plasma half-life,long duration of action, and demonstrated cardioprotective properties. We hypothesized that it might be effective at attenuating the adverse impact observed on the coronary compartment and myocardium in the transition phase to heart failure in the UM-X7.1 cardiomyopathic (CM) hamster. METHODS: The effects of 4-month exposure to lercanidipine 3 and 10 mg/kg (daily oral administration) Were evaluated in 150-day-old CM hamsters and in agematched normal hamsters. Coronary reactivity (reactive hyperemia to 30-s coronary occlusion) and the response to the administration of acetylcholine (100 nmol/L) and sodium nitroprusside (1 μmol/L) were assessed monthly, using the isolated perfused heart model. The left ventricular chamber dilatation index and wall thickness, myocardial fibrosis and myocardial capillary density (papillary muscle) were estimated in selected subgroups at monthly intervals. RESULTS     

The vascular effects of rotigaptide in vivo in man

Endothelium-derived hyperpolarising factor (EDHF) causes vasorelaxation and may contribute to the release of the endogenous fibrinolytic factor, tissue-plasminogen activator (t-PA). Rotigaptide enhances communication via the connexin 43 gap junction subunit and may potentiate the vascular actions of EDHF. The aims of the present study were therefore to determine whether rotigaptide influences basal and stimulated endothelium-dependent vasodilatation and t-PA release in vivo in man. Using venous occlusion plethysmography, forearm blood flow was measured in 27 healthy volunteers during intra-brachial infusions of rotigaptide (0.25-25 nmol/min) alone, or co-administered with endothelium-dependent (acetylcholine [5-20 microg/min] and bradykinin [30-300 pmol/min]) and independent (sodium nitroprusside [2-8 microg/min]) vasodilators in the presence or absence of aspirin and the 'nitric oxide clamp'. The 'nitric oxide clamp' inhibits endogenous nitric oxide synthesis with L-N-monomethylarginine and restores resting blood flow with the exogenous nitric oxide donor, sodium nitroprusside. Basal blood flow was unaffected by rotigaptide (P=NS). Acetylcholine, bradykinin and sodium nitroprusside all caused dose-dependent vasodilatation in the presence and absence of aspirin and the 'nitric oxide clamp' (P< or =0.005 for all). These responses were unaffected by rotigaptide (P=NS). Bradykinin caused t-PA antigen and activity release (P=0.04, P<0.0001, respectively) that was unaffected by rotigaptide. Augmentation of connexin 43 communication has no effect on basal vascular tone and does not enhance endothelium-dependent or independent vasodilatation, or t-PA release in the forearm arterial circulation of healthy men. It remains to be established whether augmentation of connexin 43 communication improves endothelial function in patients with vascular disease.     

Different modulation by Ca2+-activated K+ channel blockers and herbimycin of acetylcholine- and flow-evoked vasodilatation in rat mesenteric small arteries

1. The present study addressed whether endothelium-dependent vasodilatation evoked by acetylcholine and flow are mediated by the same mechanisms in isolated rat mesenteric small arteries, suspended in a pressure myograph for the measurement of internal diameter. 2. In pressurized arterial segments contracted with U46619 in the presence of indomethacin, shear stress generated by the flow evoked relaxation. Thus, in endothelium-intact segments low (5.1+/-0.6 dyn cm(-2)) and high (19+/-2 dyn cm(-2)) shear stress evoked vasodilatations that were reduced by, respectively, 68+/-11 and 68+/-8% (P<0.05, n=7) by endothelial cell removal. Acetylcholine (0.01-1 microM) evoked concentration-dependent vasodilatation that was abolished by endothelial cell removal. 3. Incubation with indomethacin alone did not change acetylcholine and shear stress-evoked vasodilatation, while the combination of indomethacin with the nitric oxide (NO) synthase inhibitor, N(G),N(G)-asymmetric dimethyl-L-arginine (ADMA 1 mM), reduced low and high shear stress-evoked vasodilatation with, respectively, 52+/-15 and 58+/-10% (P<0.05, n=9), but it did not change acetylcholine-evoked vasodilatation. 4. Inhibition of Ca(2+)-activated K(+) channels with a combination of apamin (0.5 microM) and charybdotoxin (ChTX) (0.1 microM) did not change shear stress- and acetylcholine-evoked vasodilatation. In the presence of indomethacin and ADMA, the combination of apamin (0.5 microM) and ChTx (0.1 microM) increased contraction induced by U46619, but these blockers did not change the vasodilatation evoked by shear stress. In contrast, acetylcholine-evoked vasodilatation was abolished by the combination of apamin and charybdotoxin. 5. In the presence of indomethacin, the tyrosine kinase inhibitor, herbimycin A (1 microM), inhibited low and high shear stress-evoked vasodilatation with, respectively, 32+/-12 and 68+/-14% (P<0.05, n=8), but it did not change vasodilatation induced by acetylcholine. In the presence of indomethacin and ADMA, herbimycin A neither changed shear stress nor acetylcholine-evoked vasodilatation. 6. The present study suggests that Ca(2+)-activated K(+) channels sensitive for the combination of apamin and ChTx are involved in acetylcholine-evoked, mainly non-NO nonprostanoid factor-mediated, vasodilatation, while an Src tyrosine kinase plays a role for flow-evoked NO-mediated vasodilatation in rat mesenteric small arteries.     

N-nitro L-arginine causes coronary vasoconstriction and inhibits endothelium-dependent vasodilatation in anaesthetized greyhounds.

1. The effect of N-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide biosynthesis, on large coronary artery diameter and coronary blood flow was examined in anaesthetized greyhounds. The effects of L-NNA on the coronary vascular responses to acetylcholine (ACh), glyceryl trinitrate (GTN) and 5-hydroxytryptamine (5-HT) were also assessed. 2. L-NNA (5 mg kg-1), infused into the left circumflex coronary artery, increased systemic mean arterial pressure and decreased the external diameter of the artery. Infusion of L-NNA decreased coronary blood flow in 5 of the 7 dogs tested and increased mean coronary resistance but neither of these effects was statistically significant. There was no change in heart rate. 3. Intra-arterial injection of both ACh (0.01-0.05 micrograms kg-1) and GTN (0.1-0.5 micrograms kg-1) increased large coronary artery diameter and coronary blood flow. Coronary vascular responses to the endothelium-dependent vasodilator ACh were significantly reduced by L-NNA, whereas the responses to the endothelium-independent vasodilator GTN were not significantly affected. 4. 5-HT (0.1 microgram kg-1, injected into the left circumflex coronary artery) decreased coronary artery diameter but increased coronary blood flow. After the administration of L-NNA the 5-HT-induced dilatation of the coronary resistance vessels was significantly attenuated whereas the constriction of the circumflex coronary artery was increased in 3 out of 3 dogs in which diameter could be measured, although the latter effect was not statistically significant. 5. These data indicate that L-NNA causes coronary and systemic vasoconstriction and selectively inhibits endothelium-dependent vasodilatation in the coronary circulation of the anaesthetized greyhound.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vasopressin effects on the coronary circulation after a short ischemia in anesthetized goats: role of nitric oxide and prostanoids

To examine the coronary effects of arginine-vasopressin during reperfusion after a short ischemia, left circumflex coronary artery flow was electromagnetically measured, and 15 min total occlusion of this artery followed by reperfusion was induced in anesthetized goats (five nontreated, five treated with the inhibitor of nitric oxide synthesis Nomega-nitro-L-arginine methyl ester (L-NAME) and five treated with the inhibitor of cyclooxygenase meclofenamate). The vasoactive drugs and L-NAME were intracoronarily injected, and meclofenamate by i.v. route. At 60 min of reperfusion, coronary vascular conductance was not changed significantly in nontreated and was decreased by 35% (P<0.01) in L-NAME-treated and by 30% (P<0.01) in meclofenamate-treated animals. During reperfusion, the coronary vasodilatation with acetylcholine (3-100 ng) and sodium nitroprusside (1-10 microg) was not altered in nontreated animals, and the vasodilatation with acetylcholine but not with sodium nitroprusside was partially decreased in L-NAME--but not in meclofenamate-treated animals. The vasoconstriction in response to arginine-vasopressin (0.03-0.3 microg) was increased during reperfusion in nontreated, was not changed in L-NAME-treated and was decreased in meclofenamate-treated animals. Therefore, it is suggested that during reperfusion after a short ischemia: (1) the coronary vasodilator reserve is preserved; (2) the coronary vasodilatation with acetylcholine is also preserved, but in this vasodilatation, the role of nitric oxide may be attenuated and prostanoids may be not involved; and (3) the coronary vasoconstriction with arginine-vasopressin is increased, probably due to both attenuation of the modulatory role of nitric oxide and the release of vasoconstrictor prostanoids.     

Impaired vasodilatation response to amrinone in the forearm of patients with congestive heart failure: role of endothelium-derived nitric oxide

Recent in vitro experiments have shown that amrinone enhances the release of nitric oxide (NO) from the endothelium and induces NO mediated vasodilatation. This in vivo study examined whether amrinone causes vasodilatation mediated by endothelium-derived NO, and whether this effect is attenuated in patients with endothelial dysfunction. Eight patients with congestive heart failure and 10 age- and sex-matched healthy volunteers were studied. Forearm blood flow (FBF) was measured before and during infusion of drugs of acetylcholine, amrinone, and nitroglycerin in incremental doses. After the completion of these measurements, 100 micromol of N(G)-monomethyl-L-arginine (L-NMMA) was infused intraarterially. Thereafter, FBF measurement in response to incremental doses of amrinone was repeated. Infusion of incremental doses of amrinone caused a comparable increase in amrinone plasma concentration in both groups. Baseline FBF was 3.2+/-0.79 ml/min/100 ml in controls vs. 2.91+/-0.79 ml/min/100 ml in patients (p = 0.43). In both groups, FBF increased in response to acetylcholine, amrinone, and nitroglycerin. During infusion of the highest dose of nitroglycerin, FBF was not different between the two groups (p = 0.51); however, FBF during infusion of the highest doses of acetylcholine and amrinone was significantly less in patients than in controls: 9.75+/-2.69 vs. 24.87+/-8.65 ml/min/100 ml (p < 0.001) and 3.79+/-1.21 vs. 7.15+/-2.06 ml/min/100 ml (p < 0.001), respectively. L-NMMA significantly depressed the increase in FBF in response to amrinone in controls, but not in patients. In conclusion, the selective PDE III inhibitor, amrinone, has endothelium-derived NO-mediated vasodilating effects in addition to direct effects. This property may be impaired in patients with endothelial dysfunction.     

Effects of oral beraprost sodium, a prostaglandin I2 analogue, on endothelium dependent vasodilatation in the forearm of patients with coronary artery disease

1. Previous clinical studies with prostaglandin I(2) (PGI(2)) analogue beraprost sodium suggested the potential effects on protection of cardiovascular events in patients with peripheral artery disease. Although the mechanism is not well known, experimental studies have shown protective effects of endothelial cells. This study was designed to examine the effects of beraprost sodium on vascular endothelial function in the forearm of patients with coronary artery disease. 2. Beraprost sodium (120 microg/day) was orally administered to 14 coronary artery disease patients for 4 weeks and then stopped for 4 weeks. Eleven control patients did not receive beraprost sodium treatment. Reactive hyperemia was induced in the forearm, endothelium-dependent vasodilatation was assessed by plethysmography, and urinary 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) was measured at baseline, 4 weeks and 8 weeks. 3. Both groups had similar reactive hyperemic responses at baseline. In the control group, reactive hyperemic response and urinary 8-iso-PGF(2alpha) remained unchanged for 8 weeks. In the beraprost group, maximum forearm blood flow increased significantly (P = 0.01) after 4 weeks of treatment and returned to baseline at 8 weeks. Duration of hyperemia increased significantly (P = 0.003) after 4 weeks, and remained greater than baseline at 8 weeks (P = 0.02). Urinary 8-iso-PGF(2alpha) decreased significantly (P = 0.03) after 4 weeks, and tended to be lower at 8 weeks (P = 0.07). Changes in reactive hyperemia correlated weakly but significantly with changes in 8-iso-PGF(2alpha) (P < 0.001). 4. Beraprost sodium decreased oxidative stress and improved forearm endothelium-dependent vasodilatation in coronary artery disease patients. The favorable effects on vascular endothelium could potentially lead to a decrease in vascular events.     

Influence of the endothelium, nitric oxide and serotonergic receptors on coronary vasomotor responses evoked by ergonovine in conscious dogs.

1. The respective contributions of coronary vascular endothelium, nitric oxide (NO) and serotonergic receptors to the effects of ergonovine on large and small coronary arteries were investigated in conscious dogs. 2. In seven dogs with an endothelium intact, ergonovine (30 - 1000 microg, i.v.) induced a biphasic response on large coronary artery with an early and transient vasodilatation (up to +2.9+/-0.5% from 3310+/-160 microm, P<0.01) followed by a sustained vasoconstriction (down to -4.9+/-0.5%, P<0.001) which occurred simultaneously with a sustained increase in coronary blood flow (CBF) (up to +100+/-26% from 28+/-4 ml min(-1), P<0.001). After endothelium removal (balloon angioplasty), the ergonovine-induced vasodilatation was abolished and vasoconstriction potentiated (-6.4+/-0.9% after vs -4.9+/-0.5% before endothelium removal, P<0.01). 3. After blockade of NO synthesis by Nomega-nitro-L-arginine (30 mg kg(-1)) in four other dogs, the early vasodilatation induced by ergonovine was abolished but the delayed vasoconstriction as well as the increase in CBF remained unchanged. 4. Both ketanserin and methiothepin (0.3 mg kg(-1)) abolished the early vasodilatation and reduced the delayed vasoconstriction induced by ergonovine. Ketanserin decreased and methiothepin abolished the reduction in coronary resistance induced by ergonovine. 5. Thus, the complex interactions between vascular endothelium and serotonergic receptors to ergonovine-induced constriction of large coronary arteries might explain the induction of coronary spasms in patients with endothelial dysfunction.     

Differential effects of L-arginine on the inhibition by NG-nitro-L-arginine methyl ester of basal and agonist-stimulated EDRF activity.

1. An isolated, buffer-perfused rabbit ear preparation was used to investigate the influence of NG-nitro-L-arginine methyl ester (L-NAME) on endothelium-dependent vasodiltation and modulation of vasoconstrictor responses and vascular conductance. 2. Acetylcholine (0.55 pmol-1.6 nmol) caused dose-related vasodilatation of preparations constricted by the combination of 5-hydroxytryptamine and histamine (both 1 microM), with an ED50 = 31.1 +/- 7.8 pmol and a maximum dilatation of 69.9 +/- 4.3%. In the presence of 10 microM L-NAME the dose-response for vasodilator effects was shifted significantly (P less than 0.001) to the right (ED50 = 3.07 +/- 1.18 nmol) and there was a significant (P less than 0.01) depression of the maximum response (Rmax = 44.3 +/- 4.0%). The higher concentration of 100 microM L-NAME completely abolished vasodilatation to acetylcholine. L-Arginine (10 mM) did not reverse the inhibitory actions of L-NAME at either concentration. 3. L-NAME 100 microM, augmented vascular tone induced by 1 microM 5-hydroxytryptamine and 1 microM histamine, thus altering the characteristics of both pressure/flow and conductance/flow relationships such that conductance was reduced at all flow rates. The augmentation of constrictor tone was reversed in a concentration-dependent manner by L-arginine (10 microM-10 mM) and the effect of L-NAME on the conductance/flow relationships was similarly reversed by 10 mM L-arginine. The augmentation of tone was endothelium-dependent as it did not occur following functional destruction of the endothelium by perfusion of the vascular bed with the detergent CHAPS (0.3%) for 150s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine artery function in a mouse model of pregnancy complicated by diabetes

It has been demonstrated previously that endothelium-dependent vasodilatation is impaired in myometrial arteries from women with gestational diabetes, which may play a role in mediating complications observed in diabetic pregnancies. It is not known which aspects of endothelium-dependent vasodilatation are impaired, thus a mouse model of pregnancy complicated by streptozotocin-induced diabetes was established to investigate underlying mechanisms. Uterine arteries from term-pregnant, diabetic and control C57Bl6/J mice were assessed using acetylcholine (ACh; 10(-10)-10(-5)M) in the presence or absence of a nitric oxide (NO) synthase inhibitor (L-NNA; 10(-5)M), a cyclooxygenase (COX) inhibitor (indomethacin; 10(-5)M) or the two in combination. Sensitivity to ACh was comparable between diabetic and control mice. However, the contribution of endothelium-dependent vasodilators was significantly altered. L-NNA significantly inhibited the relaxation of arteries from diabetic compared to control mice (65+/-11% vs 18+/-6%; p<.05). L-NNA and indomethacin significantly inhibited the relaxation of arteries from diabetic mice compared to control (87+/-5% vs 33+/-14%; p<0.05). These data indicate that endothelium-dependent relaxation of the uterine artery of control, pregnant mice was largely mediated by the non-NO/non-COX component. Surprisingly, arteries from diabetic mice were primarily dependent on NO, which may affect compensatory capacity as the disease progresses.     

Acetylcholine-induced relaxation in blood vessels from endothelial nitric oxide synthase knockout mice

1. Isometric tension was recorded in isolated rings of aorta, carotid, coronary and mesenteric arteries taken from endothelial nitric oxide synthase knockout mice (eNOS(-/-) mice) and the corresponding wild-type strain (eNOS(+/+) mice). The membrane potential of smooth muscle cells was measured in coronary arteries with intracellular microelectrodes. 2. In the isolated aorta, carotid and coronary arteries from the eNOS(+/+) mice, acetylcholine induced an endothelium-dependent relaxation which was inhibited by N(omega)-L-nitro-arginine. In contrast, in the mesenteric arteries, the inhibition of the cholinergic relaxation required the combination of N(omega)-L-nitro-arginine and indomethacin. 3. The isolated aorta, carotid and coronary arteries from the eNOS(-/-) mice did not relax in response to acetylcholine. However, acetylcholine produced an indomethacin-sensitive relaxation in the mesenteric artery from eNOS(-/-) mice. 4. The resting membrane potential of smooth muscle cells from isolated coronary arteries was significantly less negative in the eNOS(-/-) mice (-64.8 +/- 1.8 mV, n = 20 and -58.4 +/- 1.9 mV, n = 17, for eNOS(+/+) and eNOS(-/-) mice, respectively). In both strains, acetylcholine, bradykinin and substance P did not induce endothelium-dependent hyperpolarizations whereas cromakalim consistently produced hyperpolarizations (- 7.9 +/- 1.1 mV, n = 8 and -13.8 +/- 2.6 mV, n = 4, for eNOS(+/+) and eNOS(-/-) mice, respectively). 5. These findings demonstrate that in the blood vessels studied: (1) in the eNOS(+/+) mice, the endothelium-dependent relaxations to acetylcholine involve either NO or the combination of NO plus a product of cyclo-oxygenase but not EDHF; (2) in the eNOS(-/-) mice, NO-dependent responses and EDHF-like responses were not observed. In the mesenteric arteries acetylcholine releases a cyclo-oxygenase derivative.     

Coronary effects of vasopressin during partial ischemia and reperfusion in anesthetized goats. Role of nitric oxide and prostanoids

To examine the coronary effects of arginine-vasopressin and its interaction with nitric oxide and prostanoids during partial ischemia and reperfusion, left circumflex coronary artery flow was electromagnetically measured and partial occlusion of this artery was induced for 60 min, followed by reperfusion in anesthetized goats (seven non-treated, six treated with N(W)-nitro-L-arginine methyl esther (L-NAME) and five with meclofenamate). During partial coronary occlusion, coronary vascular conductance decreased by 20-31% (P<0.01), and the coronary vasodilatation in response to acetylcholine (3-100 ng) and sodium nitroprusside (1-10 microg) was much reduced in every case; the vasoconstriction in response to arginine-vasopressin (0.03-0.3 microg) was attenuated in non-treated animals; this attenuation was reversed by L-NAME and was accentuated by meclofenamate. At 30 min of reperfusion, coronary vascular conductance remained decreased by 11-25% (P<0.05 or P<0.01), and the vasodilatation in response to acetylcholine and sodium nitroprusside as well as the vasoconstriction with arginine-vasopressin was as in the control and comparable in the three groups of animals. These results suggest: (1) that, during ischemia, the coronary vasodilator reserve is greatly reduced and the vasoconstriction with arginine-vasopressin is attenuated, with preservation of the modulatory role of nitric oxide and probable involvement of vasoconstrictor prostanoids in this vasoconstriction; and (2) that, during reperfusion, the coronary vasodilator reserve and the coronary reactivity to acetylcholine and arginine-vasopressin recover, but the modulatory role of nitric oxide in this reactivity may be attenuated.     

Cigarette smoking in men and vascular responsiveness

AIMS: Smoking is a major risk factor for developing atherosclerosis. In order to understand the vascular abnormalities observed in smokers, we investigated vascular responsiveness in cigarette smokers. METHODS: We performed two consecutive matched group comparative studies to investigate vascular responsiveness using venous occlusion plethysmography. The mean effects of three incremental doses of each vasoactive agent are presented. Both studies compared smokers with nonsmokers. RESULTS: The first investigated 68 subjects (smokers = 29; mean +/- s.d. ages; 24 +/- 6 vs 25 +/- 5 years; P = NS) and found smoking was associated with a significant blunting of the flow ratio between treated and untreated arms to endothelium-dependent vasodilatation to acetylcholine (mean +/- s.d., nonsmokers vs smokers) 4.07 +/- 2.18 vs 3.42 +/- 1.79 (P = 0.04, 95% CI 0.02, 1.12). By contrast, there was no significant difference in the responses to the endothelium-independent vasodilators sodium nitroprusside and verapamil. Smoking was also associated with a significant impairment in endothelium-dependent vasoconstriction induced by monomethyl-L-arginine (L-NMMA) 0.78 +/- 0.22 vs 0.87 +/- 0.21 (P = 0.006, 95% CI -0.14, -0.02) and a trend to blunted endothelium-independent vasoconstrictor responses to noradrenaline. In the second study we investigated the response to angiotensin I and II in 23 subjects (smokers = 12; mean +/- s.d. ages; 34 +/- 10 vs 32 +/- 11 years). There was significant impairment in smokers of the mean vasoconstrictor response to angiotensin I 0.51 +/- 0.15 vs 0.59 +/- 0.16 (nonsmokers vs smokers; P = 0.003, 95% CI -0.13, -0.03) and a nonsignificant trend towards impairment of the response to angiotensin II. CONCLUSIONS: Cigarette smoking in male volunteers is associated with blunted basal and stimulated nitric oxide bioactivity. Endothelial independent vasodilator responses (to nitroprusside and verapamil) were unaltered in smokers. A defect in the vasoconstrictor response to angiotensin I was also seen.     

辛伐他汀对冠心病患者血浆一氧化氮、一氧化氮合酶的影响

目的探讨辛伐他汀对冠心病患者血浆NO和NOS的影响。方法将98例冠心病住院患者随机分为常规治疗组、辛伐他汀组及联合治疗组,采用硝酸还原酶法,在治疗前后抽血检测血中NO和NOS水平。结果各组冠心病患者在8周前,其血浆NO和NOS水平没有差异（F=4．86,3．53 P〉0．05）,在治疗8周后存在着明显的差异（F=17．63,11．07P〈0．05）,各组在治疗后血浆NO和NOS水平均明显增高,以联合治疗组增高最明显,其次是辛伐他汀组和常规治疗组。结论辛伐他汀可通过增加血浆NO和NOS的浓度来改善冠心病患者的血管内皮功能,该作用可能是通心络防治冠心病的机制之一。