Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “vasodilation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed2006

Pharmacological mechanisms involved in the vasodilator effects of extracts from Echinodorus grandiflorus.

We investigated the vascular effects of a crude aqueous extract (AEEG) of Echinodorus grandiflorus (Alismataceae) using the in vitro experimental models of the rabbit isolated aorta and perfused kidney. Echinodorus grandiflorus, a native semi-aquatic plant widely distributed in Brazil, has been extensively used in Brazilian folk medicine for the treatment of high blood pressure and inflammatory diseases. The bolus injection of AEEG (0.1-10 mg) into the rabbit renal circulation pre-contracted with norepinephrine induced marked and dose-dependent vasodilator responses (maximum of 37+/-4%; n=6; P<0.001), which was similar to that induced by injection of 10 mmol acetylcholine (41+/-3%). Moreover, AEEG elicited a significant and concentration-dependent relaxation in the endothelium-intact, but not endothelium-denuded aortic rings, reaching the maximum of 81+/-5% (n=7, P<0.001). Inhibition of the nitric oxide-cGMP pathway with L-NAME (100 microM) or Methylene Blue (20 microM) reduced maximum relaxation induced by AEEG from 81+/-5% to 46+/-3 and 45+/-3%, respectively (n=7, P<0.001). A similar reduction was obtained with the incubation of the aortic rings with the selective PAF receptor antagonist WEB 2086 (10 microM) (from 81+/-5% to 55+/-3%; n=7; P<0.01). Conversely, blockade of muscarinic receptors with atropine (10 microM) did not affect the vasodilator effects of AEEG, while inhibition of the enzyme cyclooxigenase not only did not block, but rather potentiated vasodilation induced by AEEG (n=7, P<0.001). Finally, blockade of Ca(2+)- and ATP-activated K(+) channels using the specific blockers charydbotoxin (100 nM) and glibenclamide (3 microM), respectively, did not modify aortic relaxation induced by AEEG. We conclude that water-soluble extracts from leaves of Echinodorus grandiflorus elicit an endothelium-dependent, nitric oxide and PAF receptor-mediated vasodilation in rabbit aortic rings, which does not appear to involve the generation of vasodilating prostaglandins or the activation of K(+) channels. This potent vasodilator effect of the extracts was confirmed in the isolated rabbit renal circulation.

Alismataceae↗
PubMed2004

Role of bradykinin in gastric vasodilation caused by hypertonic saline and acid back diffusion.

Protective vasodilation in response to tissue injury and acid back diffusion is associated with release of bradykinin in the rat stomach. We hypothesized that bradykinin might be involved in mechanisms behind such vasodilation via influence on mast cells and sensory neurons. Acid back diffusion after mucosal barrier disruption with hypertonic saline evoked degranulation of mast cells in the rat stomach wall. Acid back diffusion was also associated with increased luminal release of histamine and gastric blood flow in normal rats, but not in mast cell-deficient rats. Bradykinin (BK(2)) receptor blockade inhibited degranulation of submucosal mast cells in the stomach and attenuated gastric vasodilation both in response to acid back diffusion and after stimulation of sensory neurons with capsaicin. Gastric vasodilation caused by mucosal injury with hypertonic saline alone was associated with degranulation of mucosal mast cells. These events were unaffected by inhibition of prostaglandin synthesis, whereas bradykinin (BK(2)) receptor blockade was associated with abolished vasodilation and inhibition of mucosal mast cell degranulation. We conclude that bradykinin is involved in gastric vasodilation caused by hypertonic injury alone via influence on mast cells, and by acid back diffusion via influence on both sensory neurons and mast cells.

Animals↗
PubMed2006

Endothelium-dependent vasodilator effect of Euterpe oleracea Mart. (Açaí) extracts in mesenteric vascular bed of the rat.

Açai (Euterpe oleracea Mart.) a fruit from the Amazon region, largely consumed in Brazil is rich in polyphenols. Experiments were undertaken to determine whether hydro-alcoholic extract obtained from stone of açaí induces a vasodilator effect in the rat mesenteric vascular bed precontracted with norepinephrine (NE) and, if so, to elucidate the underlying mechanism. Açai stone extract (ASE, 0.3-100 microg) induced a long-lasting endothelium-dependent vasodilation that was significantly reduced by N(G)-nitro-l-arginine methyl ester (l-NAME) and (1)H-[1,2,3] oxadiazolo [4,4-a] quinoxalin-l-one (ODQ) and abolished by KCl (45 mM) plus l-NAME. In vessels precontrated with NE and KCl (45 mM) or treated with K(Ca)(+2) channel blockers (charybdotoxin plus apamin), the effect of ASE was significantly reduced. However this effect is not affect by indomethacin, glybenclamide and 4-aminopiridine. Atropine, pyrilamine, yohimbine and HOE 140 significantly reduced the vasodilator effect of acetylcholine, histamine, clonidine and bradykinin, respectively, but did not change the vasodilator effect of ASE. In cultured endothelial cells ASE (100 microg/mL) induced the formation of NO that was reduced by N(G)-nitro-l-arginine (l-NA, 100 microM). The present study demonstrates that the vasodilator effect of ASE is dependent on activation of NO-cGMP pathway and may also involve endothelium-derived hyperpolarizing factor (EDHF) release. The vasodilator effect suggest a possibility to use ASE as a medicinal plant, in the treatment of cardiovascular diseases.

Animals↗
PubMed2002

Effect of atorvastatin on endothelium-dependent vasodilation in postmenopausal women with average serum cholesterol levels.

After menopause, most healthy women show an impairment of peripheral vasodilation and an increase of plasma cholesterol levels. Statins have been shown to improve endothelial function in hypercholesterolemic men and women. The present study tests whether atorvastatin (10 mg) influences endothelium-dependent vasodilation in postmenopausal normocholesterolemic women. Twenty-eight healthy, postmenopausal women (mean age 51 +/- 2 years) with serum total cholesterol and low-density lipoprotein cholesterol within the desirable range entered a double-blind, single-crossover study. Postmenopausal women were randomized to receive either atorvastatin (10 mg/day) or placebo for 10 days and then crossed to the complementary treatment. Endothelium-dependent and -independent responses were assessed by means of strain-gauge plethysmography before and after intra-arterial infusion of acethylcholine (ACh) and sodium nitroprusside, in comparison to physiologic saline. The nitric oxide pathway was evaluated by repeating the infusion of ACh during admininstration of L-arginine and (G)-monomethyl-L-arginine (L-NMMA). Serum lipoproteins were not significantly modified by the active treatment. The vasodilation induced by ACh was significantly higher in the atorvastatin-treated women compared with the placebo-treated group (24 +/- 3 vs 13 +/- 2 ml/100 ml tissue/min, p <0.01). In contrast, responses to the endothelium-independent vasodilator sodium nitroprusside were not significantly modified by atorvastatin. The ACh-stimulated vasodilation induced by atorvastatin was additionally potentiated by L-arginine (800 +/- 105% vs 370 +/- 60%, p <0.05) and blunted by L-NMMA. No correlation was found between changes in plasma cholesterol and improvement in forearm blood flow. Our data show that the beneficial effect of atorvastatin on endothelium-dependent vasodilation is independent from changes in the lipid profile.

Acetylcholine↗
PubMed2003

Local anesthesia reduces the maximal skin vasodilation during iontophoresis of sodium nitroprusside and heating.

AIM: To evaluate the effect of local anesthesia on the skin vasodilation induced by the iontophoresis of sodium nitroprusside and heating. METHODS: Skin vascular reactivity, in response to iontophoresis of sodium nitroprusside (SNP), was evaluated at the forearm and foot in 13 neuropathic diabetic (DN) and 11 nonneuropathic diabetic (D) patients and 9 healthy, nondiabetic subjects who served as controls (C). The direct (DI) and nerve axon reflex-related (N-V) vasodilation were measured by using two single-point laser Doppler probes. The vasodilation in response to local warming was also assessed. A topical anesthetic was applied on the contralateral forearm and foot and all the measurements were repeated. RESULTS: Dermal anesthesia resulted in a reduction of the direct vasodilation to SNP at the forearm [C: 58.1 +/- 16, D: 60.6 +/- 11%, and DN: 48.3 +/- 37% (postanesthesia percentage of reduction; mean +/- SEM), P<0.01] and at the foot in all three groups (D: 38.5 +/- 12%, P<0.01; C: 27.2 +/- 14% and DN: 11.3 +/- 17.5%, P=NS). The N-V related vasodilation was very low before and did not change after local anesthesia. The postanesthesia hyperemic response to warming was significantly reduced at low temperatures but did not change at 44 degrees C. CONCLUSION: The sodium nitroprusside-related vasodilation is reduced after local anesthesia in a similar way in healthy subjects and diabetic patients with and without neuropathy. The response to heating is also reduced at low temperatures. This indicates a stabilizing effect of local anesthesia on the smooth muscle cell.

Administration, Topical↗
PubMed2002

Vasodilator effect of angiotensin-(1-7) in mature and sponge-induced neovasculature.

Angiotensin-(1-7) (Ang-(1-7)), a peptide constituent of the renin-angiotensin system, has been shown to act as a vasodilator mediator in pre-existing (skin) and newly formed vasculatures (14-day-old sponge implants). Blood flow was determined by the outflow rate of sodium fluorescein applied intradermally or intraimplant and the results were expressed in t(1/2) values (time taken for the fluorescence to reach 50% of the peak in the systemic circulation). We showed that the t(1/2) value was significantly lower (4.1+/-0.46) in the implants compared with the cutaneous vasculature (5.7+/-0.5). Ang-(1-7) 20 ng was able to decrease t(1/2) values in both vasculatures. The specific receptor antagonist, D-Ala7-Ang-(1-7) (A-779), prevented Ang-(1-7)-induced vasodilation and altered the basal vascular tone of the implants. The vasodilator effect was also abolished by nitric oxide (NO) synthase inhibitors in both vasculatures and by indomethacin in the implant. Selective AT(1) and AT(2) receptor antagonists did not alter the vasodilation induced by the peptide. These results establish the vasodilator effect of Ang-(1-7) in the cutaneous and implant vasculature and that the peptide is produced endogenously by the fibrovascular tissue, and suggest that this peptide contributes for the vasodilation found in newly formed vascular beds (wound healing, chronic inflammatory processes and tumors).

Angiotensin I↗
PubMed1999

Acetylcholine but not sodium nitroprusside exerts vasodilation in pulmonary hypertension secondary to chronic congestive heart failure.

BACKGROUND: Reduced endothelium-dependent vasodilation contributes to the development of pulmonary hypertension in chronic congestive heart failure (CHF). We investigated pulmonary endothelium-dependent and independent vasodilation in patients with CHF. METHODS: We studied 42 patients with CHF (age 55 +/- 10, NYHA Classes II-III, left ventricular ejection fraction 27 +/- 10%, mean PAP 29 +/- 12 mmHg). The endothelial vasodilator capacity of pulmonary resistance vessels was assessed by the infusion of acetylcholine into a pulmonary artery branch while measuring the blood flow velocity with a Doppler flow wire. For comparison endothelium-independent vasodilation was measured with the response to sodium nitroprusside. The conductance vessel diameter (4.4 +/- 0.2 mm) was determined by intravascular ultrasound. Acetylcholine was administered at concentrations of 10(-6) to 10(-4) mol/l, sodium nitroprusside was administered at concentrations of 0.125 and 0.25 microg/kg per min. The effects on conductance vessel diameter were investigated in 12 patients by the measurement of diameter and flow velocity following the administration of acetylcholine and sodium nitroprusside. RESULTS: Acetylcholine markedly increased blood flow velocity (+39 +/- 7% at 10(-4) mol/l; p < .05). This correlated with the baseline PAP (r = 0.58; p < .05) and pulmonary vascular resistance (r = 0.58; p < .05). Sodium nitroprusside caused a small increase in the flow velocity (5 +/- 2% at 0.125, 12 +/- 4% at 0.25 microg/kg per minute; p < .05) that was accompanied by systemic vasodilation. The conductance vessel diameter was unchanged after acetylcholine was administered and was only marginally decreased after the administration of sodium nitroprusside. CONCLUSIONS: In CHF acetylcholine reveals preserved receptor-mediated endothelial vasodilation, that is positively correlated to pulmonary hypertension, and cannot be reproduced by sodium nitroprusside.

Acetylcholine↗
PubMed1998

Captopril, but not nifedipine, improves endothelium-dependent vasodilation in hypertensive patients.

The present study aimed to investigate the influence of the angiotensin-converting enzyme (ACE)-inhibitor captopril and the Ca-antagonist nifedipine on endothelium-dependent vasodilation (EDV) in the forearm of hypertensive patients. Twenty-three middle-aged untreated hypertensive patients underwent evaluation of EDV and endothelium-independent vasodilation (EIDV) in the forearm, by means of local intra-arterial infusions of methacholine (MCh, evaluating EDV) and sodium-nitroprusside (SNP, evaluating EIDV), before and 1 h after intake of either captopril (25 mg) or nifedipine (10 mg) in a randomised, double-blind fashion. A matched normotensive control group was investigated at baseline conditions only. Five of the hypertensives were also evaluated after 3 months of treatment with captopril 25 mg twice daily in an open pilot study. First, the vasodilation induced by methacholine (MCh), but not SNP, was significantly attenuated in the hypertensive patients compared to the normotensive controls (P < 0.001 at MCh 4 microg/min). Second, although the two drugs induced a similar decline in blood pressure (BP) 1 h after administration (-11 to 10 mm Hg/-8 to 7 mm Hg), captopril significantly potentiated the vasodilator response to MCh (+32+/-13%, MCh 4 micr og/min, P < 0.01) but not SNP, while nifedipine did not significantly alter the response to either MCh or SNP. The improvement in vasodilator response to MCh induced by captopril was closely related to the reduction in BP (r = 0.72, P < 0.01). Third, in the pilot study, 3 months of captopril treatment induced a significant potentiation of the vasodilator response to MCh (+34+/-17%, MCh 4 microg/min, P < 0.05) in parallel with a significant BP reduction (-22+/-24/13+/-13 mm Hg, P < 0.05), while the response to SNP was unchanged. In conclusion, the present study confirmed that essential hypertension is associated with a defect in EDV. Furthermore, an improvement in EDV was seen in hypertensive patients shortly after administration of captopril, but not nifedipine. In addition, a significant beneficial effect on EDV was seen in a small pilot study during long-term treatment with captopril.

Aged↗
PubMed2003

Effects of posture and venous insufficiency on endothelial-dependent and -independent cutaneous vasodilation in the perimalleolar region.

OBJECTIVES: To assess the effects of posture, endothelial function and venous insufficiency on cutaneous microvascular vasodilator function in the gaiter area, in particular defining factors which may affect microangiopathy and ulcer formation. METHODS: Endothelial-dependent and -independent vasodilator responses to incremental-doses of acetylcholine (Ach) and sodium nitroprusside (SNP) were evaluated in the perimalleolar region in the supine and standing positions in middle-aged patients with isolated superficial venous insufficiency (ISVI) (n = 25) and healthy controls (n = 28) using laser Doppler fluximetry (LDF) and iontophoresis of vasodilators. RESULTS: The venoarteriolar reflex (vasoconstriction on standing) was equally present in both groups, and reduced the vasodilator responses to SNP in the upright position (e.g., for patients with ISVI, peak SNP response was 82 +/- 11 PU [standing] vs 123 +/- 15 PU [supine]). The presence of ISVI had no effect on endothelial vasodilator function in the supine position, but on standing cutaneous reactivity to Ach was significantly reduced (e.g., peak Ach response 69 +/- 8 PU [ISVI] vs 109 +/- 11 PU [controls], p < 0.003). CONCLUSIONS: Upright posture impairs cutaneous endothelial-dependent vasodilation in the gaiter area of patients with ISVI. This may be of clinical and prognostic utility in identifying which patients with uncomplicated ISVI are at highest risk of tissue breakdown and ulcer formation in the gaiter area.

Acetylcholine↗
PubMed2003

The depressor and vasodilator effects of rutaecarpine are mediated by calcitonin gene-related peptide.

Previous studies have shown that rutaecarpine has depressor and vasodilator effects, and activates vanilloid receptors to evoke calcitonin gene-related peptide (CGRP) release. In the present study, we examined whether the depressor and vasodilator effects of rutaecarpine are related to the stimulation of endogenous CGRP release via activation of vanilloid receptors in rats. Rutaecarpine (30, 100, or 300 microg/kg, i. v.) caused a depressor effect concomitantly with an increase in the plasma concentrations of CGRP in a dose-dependent manner, and the effects of rutaecarpine were abolished by pretreatment with capsaicin (50 mg/kg, s. c.) which depletes neurotransmitters in sensory nerves. In aortic and superior mesenteric arterial rings, rutaecarpine (10 (-7)-10(-5) M) or capsaicin (3 x 10(-9)-3 x 10(-6) M) caused a concentration-dependent vasodilator response, which was significantly attenuated by capsazepine (10(-5) M), a competitive vanilloid receptor antagonist, or by CGRP-(8-37) (10(-6) M), a selective CGRP receptor antagonist. After pretreatment with capsaicin (10(-5) M) for 20 min, vasodilator responses to rutaecarpine were also markedly attenuated. Similarly, pretreatment with rutaecarpine (10(-5) M) for 20 min also attenuated vasodilator responses to capsaicin. These results suggest that the depressor and vasodilator effects of rutaecarpine are related to stimulation of endogenous CGRP release via activation of vanilloid receptors in rats.

Alkaloids↗
PubMedDate not supplied

Prolonged local forearm hyperinsulinemia induces sustained enhancement of nitric oxide-dependent vasodilation in healthy subjects.

Systemic hyperinsulinemia induces enhancement of endothelium-dependent vasodilation of healthy subjects. During systemic infusion of insulin, endothelium-dependent vasodilation may be improved through a decrease in the concentration of free fatty acids. To explore the direct effect of continued insulin on the vascular endothelium, the authors infused insulin in the brachial artery for 4 h and measured the effect on endothelium-dependent vasodilation in the human forearm. Thirty-six experiments were performed in healthy subjects, mean age 47.7 +/- 1.1 years. Endothelium-dependent and -independent vasodilatation was studied during intra-arterial infusion of serotonin and sodium nitroprusside (SNP), respectively. Forearm blood flow was measured by plethysmography. Intra-arterial insulin was infused for 240 min at a constant rate and blood flow was measured hourly during stimulation of endothelium-dependent and -independent vasodilation.N(G)-monomethyl-L-arginine (L-NMMA) was coinfused to test the degree of nitric oxide (NO)-mediated vasodilation. Insulin infusion for 60 min enhanced serotonin-induced vasodilation by 37% compared to vehicle, p = .016. This increase was maintained for 4 h and was blocked by L-NMMA. The SNP response was increased by insulin but the increment was inhibited by L-NMMA. Four hours of local forearm hyperinsulinemia causes a sustained increase in endothelium dependent vasodilation in resistance vessels, which is mediated by NO.

Aged↗
PubMed1998

Pulmonary vasodilator response to adenosine triphosphate-sensitive potassium channel activation is attenuated during desflurane but preserved during sevoflurane anesthesia compared with the conscious state.

BACKGROUND: The objective of this study was to investigate the effects of sevoflurane and desflurane anesthesia on the pulmonary vasodilator response to the adenosine triphosphate-sensitive potassium channel agonist, lemakalim, compared with the response measured in the conscious state. In addition, the authors assessed the extent to which sympathetic alpha1-adrenoreceptor inhibition and cyclooxygenase pathway inhibition modulate the vasodilator response to lemakalim. METHODS: Twenty-four conditioned male mongrel dogs were chronically instrumented to measure the left pulmonary vascular pressure-flow relationship. After preconstriction with the thromboxane analogue, U46619, dose-response relationships to lemakalim were assessed on separate days in the conscious state and during sevoflurane (approximately 3.5% end-tidal) and desflurane (approximately 10.5% end-tidal) anesthesia (approximately 1.5 minimum alveolar concentration for each anesthetic agent). The effects of sympathetic alpha1-adrenoreceptor inhibition (prazosin) and cyclooxygenase inhibition (indomethacin) on the pulmonary vasodilator response to lemakalim also were assessed in the conscious and desflurane-anesthetized states. RESULTS: Neither sevoflurane nor desflurane had a net effect on the baseline left pulmonary vascular pressure-flow relationship compared with the conscious state. The magnitude of the pulmonary vasodilator response to lemakalim was preserved during sevoflurane anesthesia but was attenuated (P < 0.05) during desflurane anesthesia compared with the conscious state. The attenuated lemakalim-induced vasodilator response during desflurane anesthesia was partially reversed (P < 0.05) by pretreatment with prazosin but not indomethacin. CONCLUSION: These results indicate that adenosine triphosphate-sensitive potassium channel-mediated pulmonary vasodilation is preserved during sevoflurane anesthesia but is attenuated during desflurane anesthesia. The attenuated response to adenosine triphosphate-sensitive potassium channel activation during desflurane anesthesia is partially mediated by reflex sympathetic alpha1-adrenoreceptor vasoconstriction.

Adenosine Triphosphate↗
PubMed2001

Isradipine improves endothelium-dependent vasodilation in normotensive coronary artery disease patients with hypercholesterolemia.

OBJECTIVE: The dihydropyridine calcium antagonist isradipine has anti-atherosclerotic effects in animals and improves endothelium-mediated nitric oxide (NO)-dependent vasodilation in vitro. As improved endothelial function may be beneficial we investigated its effects in patients with a high likelihood of endothelial dysfunction. DESIGN: Thirty patients (two female, age 55.4 +/- 10.5 years) with known coronary artery disease and elevated (> 6 mmol/l) total cholesterol (cholesterol: mean 6.7 +/- 0.78 mmol/l) or a cholesterol/high density lipoproteins (HDL) ratio of > 5 not on lipid lowering therapy, participated in the study. Endothelial vasodilator function was assessed before and after double-blind, randomized administration of isradipine 5 mg/day or placebo for 3 months. METHODS: Endothelial function was assessed as forearm blood flow (FBF, venous occlusion plethysmography) responses to graded brachial artery infusions of acetylcholine (Ach), to the NO-synthase blocker NG-monomethyl-L-arginine (L-NMMA) and to the endothelium-independent vasodilator sodium nitroprusside (SNP). Blood pressure was measured either directly from the brachial arterial or by sphygmomanometer during clinic visits. RESULTS: Blood pressure was unchanged in both groups after 3 months (isradipine: 88.8 versus 92.1 mmHg; placebo: 81.0 versus 82.5 mmHg; NS) but cholesterol levels decreased similarly in both groups (isradipine: 6.7 versus 6.1 mmol/l, NS; placebo: 6.6 versus 5.9 mmol/l, P< 0.05). The vasodilator response to SNP and the decrease in FBF in response to blockade of NO synthesis by L-NMMA were unchanged in both groups. However, isradipine, but not placebo, enhanced the NO-dependent vasodilator response to Ach (P < 0.05). CONCLUSION: Isradipine improves acetylcholine-mediated vasodilation in hypercholesterolemic patients independent of changes in lipids or blood pressure.

Aged↗
PubMed1997

Oxygen-induced pulmonary vasodilation is mediated by adenosine triphosphate in newborn lambs.

In the fetal lamb, oxygen-induced pulmonary vasodilation is attenuated by the combined use of purinergic receptor P1 and P2y antagonists, which block the effect of adenosine and adenosine triphosphate (ATP), respectively, and by N(omega)-nitro-L-arginine [an inhibitor of endothelium-derived nitric oxide (EDNO) synthesis]. In the newborn lamb, oxygen-induced pulmonary vasodilation is not blocked by N(omega)-nitro-L-arginine. We investigated the role of ATP and adenosine in oxygen-induced pulmonary vasodilation in eight newborn lambs with pulmonary hypertension induced by the thromboxane mimic, U46619. The hemodynamic effects of hyperoxia, ATP, adenosine, sodium nitroprusside (SNP), and acetylcholine (ACh) were compared before and after purinergic receptor blockade with Cibacron blue (CB, a P2y-receptor antagonist) and 8-phenyltheophylline (8PT, a P1-receptor antagonist) individually, together, and on a separate day, after infusion of N(omega)-nitro-L-arginine. During pulmonary hypertension, combined pretreatment with 8PT and CB attenuated the decrease in pulmonary arterial pressure caused by hyperoxia (11.3 vs. 35.2%), ATP (10.6 vs. 32.2%), and adenosine (1.9 vs. 33.7%) without change in the effect of ACh or SNP (p < 0.05). N(omega)-Nitro-L-arginine attenuated the pulmonary vasodilation caused by ATP and ACh but not by hyperoxia, adenosine, or SNP. In the newborn lamb, the pulmonary vasodilating effect of both oxygen and ATP are attenuated by combined P1 and P2y purinergic-receptor antagonists. Postnatally, oxygen-induced pulmonary vasodilation appears to be mediated by ATP through purinergic receptors.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2002

Tetrahydrobiopterin improves impaired endothelium-dependent forearm vasodilation in patients with heart failure.

Endothelium-dependent vasodilation is impaired in patients with chronic heart failure (CHF). However, the mechanisms responsible for this effect are not fully understood. The vasodilator response to acetylcholine (ACh) has been used to examine the endothelium-dependent vasodilation in humans and is known to be mediated by nitric oxide (NO). The impaired production of NO or an increase in its degradation is thought to be responsible for the endothelial dysfunction in CHF. The aim of this study was to determine whether the decrease in availability of tetrahydrobiopterin (BH(4)), an essential cofactor of NO synthase, contributes to the impairment of endothelium-dependent vasodilation in patients with CHF. Fourteen patients with CHF (New York Heart Association functional class II-IV, age: 59 +/- 4 years, ejection fraction: 28 +/- 3%) and seven age-matched control subjects were examined. Forearm blood flow (FBF) was measured by plethysmography during an intra-arterial infusion of a graded dose of ACh (4, 8, and 16 microg/min) and sodium nitroprusside (SNP) (0.8, 1.6, and 3.2 microg/min). These procedures were repeated during a co-infusion of BH(4) (400 microg/min). The forearm vasodilator response to ACh was significantly enhanced during co-infusion of BH(4) in patients with CHF, whereas no effect was observed in healthy subjects. In contrast, the response to SNP was not affected by BH(4) in either group. The administration of BH(4) did not alter the baseline FBF in either group. These results suggest that an acute administration of BH(4 ) improves endothelium-dependent forearm vasodilation in patients with CHF.

Acetylcholine↗
PubMed1992

Effects of nitric oxide synthase inhibitors, L-NG-nitroarginine and L-NG-nitroarginine methyl ester, on responses to vasodilators of the guinea-pig coronary vasculature.

1. The effects of L-NG-nitroarginine (L-NOARG) and L-NG-nitroarginine methyl ester (L-NAME) on vasodilatation induced by ATP, substance P, 5-hydroxytryptamine (5-HT), bradykinin and sodium nitroprusside (SNP) were examined in the guinea-pig coronary bed, by use of a Langendorff technique. The effects of these inhibitors of nitric oxide synthesis were assessed on their ability to inhibit both the amplitude and the area of the vasodilator response. 2. The vasodilator responses evoked by low doses of 5-HT (5 x 10(-10)-10(-8) mol) were almost abolished by L-NAME and L-NOARG (both at 10(-5), 3 x 10(-5) and 10(-4) M), although L-NOARG (3 x 10(-5) M) was significantly less potent than L-NAME (3 x 10(-5) M) as an inhibitor of vasodilator responses to 5-HT (5 x 10(-8) mol). 3. The vasodilator responses evoked by substance P (5 x 10(-12)-5 x 10(-9) mol) were reduced in the presence of L-NAME and L-NOARG (both at 10(-5) and 3 x 10(-5) M). The response to substance P was almost abolished by L-NAME and L-NOARG (both at 10(-4) M). 4. The amplitude of the vasodilator responses to ATP (5 x 10(-11) and 5 x 10(-9)-5 x 10(-7) mol) was little affected by either L-NAME or L-NOARG (both at 10(-5), 3 x 10(-5) and 10(-4) M).7. It is concluded that in the guinea-pig coronary vasculature, the vasodilatation evoked by substance P and low doses of 5-HT is mediated almost exclusively via nitric oxide, whereas the vasodilatations evoked by ATP and bradykinin appear to involve other mechanisms in addition to the release of nitric oxide. L-NAME was a more effective agent than L-NOARG in inhibiting the vasodilator actions of 5-HT and ATP in this preparation.

Adenosine Triphosphate↗
PubMed1996

Vasodilator responses of rat isolated tail artery enhanced by oxygen- dependent, photochemical release of nitric oxide from iron-sulphur-nitrosyls.

1. The vasodilator properties and photochemical decomposition of two synthetic iron-sulphur-nitrosyl clusters (cluster A: [Fe4S4(NO)4], tetranitrosyl-tetra-mu 3-sulphido-tetrahedro-tetrairon; and B:[Fe4S3 (NO)7]-1, heptanitrosyl-tri-mu 3-thioxotetraferrate(-1)) have been investigated. Experiments were carried out on isolated, internally-perfused segments of rat tail artery. 2. Bolus injections (10 microliters) of A or B ( > 0.25 mM) delivered into the internal perfusate generated sustained (or S-type) vasodilator responses, characterized by a persistent plateau of reduced tone due to NO released from clusters which enter and become trapped within endothelial cells. Clusters were therefore irradiated with visible laser light (lambda = 457.9 or 514.5 nm) either (a) in solution, while passing through a glass tube en route to the artery; or (b) when retained within the endothelium, by illuminating the artery directly during the plateau of an S-type response. Irradiation produced an additional vasodilator response, the magnitude of which depended upon wavelength and laser beam energy. 3. The nitric oxide synthase inhibitor, NG-monomethyl-L-arginine (100 microM), had no effect on light-induced vasodilator responses. However, they were (a) blocked entirely by adding oxyhaemoglobin (5 microM) to the internal perfusate; and (b) greatly enhanced by the enzyme superoxide dismutase (150 u ml-1). 4. Photolysis of cluster B was measured by absorption spectroscopy and by detecting NO released with an electrochemical sensor. The photochemical reaction was found to be oxygen-dependent. The half-time for inactivation of cluster-derived NO was measured by interposing different lengths of tubing (i.e. time delays) between the photolysis tube and NO sensor. The steady-state probe current decayed exponentially with increasing delay time, with a t 1/2 of 21 s. The amplitudes of vasodilator responses of the tail artery also decreased exponentially by increasing the time delay (t 1/2 = 58 s). Superoxide dismutase (150 u ml-1) prevented this from happening, showing that "inactivation' of cluster-derived NO was caused by reaction with superoxide anions formed during photolysis. 5. We conclude that potentiation of vasodilator responses to iron-sulphur-nitrosyl clusters by visible light is due to an oxygen-dependent photochemical reaction which accelerates the release of ligated nitrosyl groups as free NO. Based on our measurements, we estimate that ca 100 pM NO is sufficient to produce a just-detectable additional vasodilatation and that the ED50 dose is ca 3.7 nM.

Animals↗
PubMed1999

Vasodilator responses to the endomorphin peptides, but not nociceptin/OFQ, are mediated by nitric oxide release.

The endomorphin peptides, endogenous ligands for the mu-opioid receptor, and nociceptin (orphanin FQ; OFQ), an endogenous ligand for the ORL1 receptor, have substantial vasodilator activity in the rat. The roles of nitric oxide, vasodilator prostaglandins, and the opening of K+ATP channels in mediating vasodilator responses to these novel agonists were investigated in the hindquarters vascular bed of the rat. Under constant-flow conditions, injections of the mu-selective agonists, endomorphin 1 and 2, PL017 ([N-MePhe3, D-Pro4]-morphiceptin), and DAMGO, and the ORL1 receptor agonist, nociceptin/OFQ, produced dose-dependent decreases in hindquarters perfusion pressure. Vasodilator responses to endomorphin 1, PL017, and DAMGO were attenuated by the nitric oxide synthase inhibitor L-NAME at a time when vasodilator responses to nociceptin/OFQ were not altered. Responses to endomorphin 1 and 2, PL017, DAMGO, and nociceptin/OFQ were not altered by the cyclooxygenase inhibitor sodium meclofenamate or the K+ATP channel blocker U-37883A. The results of these studies indicate that responses to endomorphin 1 and 2, PL017, and DAMGO are mediated in large part by the release of nitric oxide, while responses to nociceptin/OFQ are mediated by an L-NAME-insensitive mechanism. Moreover, these results demonstrate that responses to these peptides are not mediated by the release of vasodilator prostaglandins or K+ATP channel opening in the hindquarters vascular bed.

Adamantane↗