Enhanced role of potassium channels in relaxations to acetylcholine in hypercholesterolemic rabbit carotid artery

1994 ◽  
Vol 266 (5) ◽  
pp. H2061-H2067 ◽  
Author(s):  
S. Najibi ◽  
C. L. Cowan ◽  
J. J. Palacino ◽  
R. A. Cohen
Keyword(s):  
Nitric Oxide ◽  
Methyl Ester ◽  
Carotid Artery ◽  
Potassium Channels ◽  
Abdominal Aorta ◽  
Combined Treatment ◽  
Rabbit Carotid Artery ◽  
Calcium Dependent ◽  
Endothelium Dependent Relaxation

The effect of hypercholesterolemia for 10 wk on endothelium-dependent relaxations to acetylcholine was studied in isolated rings of rabbit carotid artery and abdominal aorta contracted with phenylephrine or elevated potassium. In these arteries obtained from hypercholesterolemic rabbits, endothelium-dependent relaxations to acetylcholine were not significantly different from those of normal rabbits. In normal and hypercholesterolemic arteries, partial relaxation persisted in the presence of NG-nitro-L-arginine methyl ester (L-NAME), which blocked acetylcholine-induced increases in arterial guanosine 3',5'-cyclic monophosphate (cGMP). Combined treatment with L-NAME and the calcium-dependent potassium-channel inhibitor, charybdotoxin, blocked relaxations in both groups, suggesting that L-NAME-resistant relaxations are mediated by an endothelium-derived hyperpolarizing factor. Charybdotoxin alone or depolarizing potassium had no significant effect on normal carotid artery or normal and hypercholesterolemic abdominal aorta but significantly inhibited relaxations of the carotid artery from cholesterol-fed rabbits. The enhanced role of calcium-dependent potassium channels and the hyperpolarizing factor in relaxation of the hypercholesterolemic carotid artery suggested by these results was likely related to the fact that acetylcholine failed to stimulate cGMP only in that artery. These data suggest that endothelium-dependent relaxation in these rabbit arteries is mediated by nitric oxide-cGMP-dependent and -independent mechanisms. In hypercholesterolemia, the contribution of nitric oxide-cGMP in the carotid artery is reduced, but a hyperpolarizing factor and calcium-dependent potassium channels maintain normal acetylcholine-induced relaxation.

Enhanced role of K+ channels in relaxations of hypercholesterolemic rabbit carotid artery to NO

1995 ◽  
Vol 269 (3) ◽  
pp. H805-H811 ◽  
Author(s):  
S. Najibi ◽  
R. A. Cohen
Keyword(s):  
Carotid Artery ◽  
Sodium Nitroprusside ◽  
Channel Blocker ◽  
Isometric Tension ◽  
K Channel ◽  
K Channels ◽  
Rabbit Carotid Artery ◽  
Cyclic Monophosphate ◽  
Endothelium Dependent Relaxation

Endothelium-dependent relaxations to acetylcholine remain normal in the carotid artery of hypercholesterolemic rabbits, but unlike endothelium-dependent relaxations of normal rabbits, they are inhibited by charybdotoxin, a specific blocker of Ca(2+)-dependent K+ channels. Because nitric oxide (NO) is the mediator of endothelium-dependent relaxation and can activate Ca(2+)-dependent K+ channels directly or via guanosine 3',5'-cyclic monophosphate, the present study investigated the role of Ca(2+)-dependent K+ channels in relaxations caused by NO, sodium nitroprusside, and 8-bromoguanosine 3',5'-cyclic monophosphate (8-Brc-GMP) in hypercholesterolemic rabbit carotid artery. Isometric tension was measured in rabbit carotid artery denuded of endothelium from normal and hypercholesterolemic rabbits which were fed 0.5% cholesterol for 12 wk. Under control conditions, relaxations to all agents were similar in normal and hypercholesterolemic rabbit arteries. Charybdotoxin had no significant effect on relaxations of normal arteries to NO, sodium nitroprusside, or 8-BrcGMP, but the Ca(2+)-dependent K+ channel blocker significantly inhibited the relaxations caused by each of these agents in the arteries from hypercholesterolemic rabbits. By contrast, relaxations to the calcium channel blocker nifedipine were potentiated to a similar extent by charybdotoxin in both groups. In addition, arteries from hypercholesterolemic rabbits relaxed less than normal to sodium nitroprusside when contracted with depolarizing potassium solution. These results indicate that although nitrovasodilator relaxations are normal in the hypercholesterolemic rabbit carotid artery, they are mediated differently, and to a greater extent, by Ca(2+)-dependent K+ channels. These data also suggest that K+ channel-independent mechanism(s) are impaired in hypercholesterolemia.

Lovastatin maintains nitric oxide—but not EDHF-mediated endothelium-dependent relaxation in the hypercholesterolemic rabbit carotid artery

1999 ◽  
Vol 142 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Ralf P. Brandes ◽  
Andreas Behra ◽  
Corinna Lebherz ◽  
Rainer H. Böger ◽  
Stefanie M. Bode-Böger ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Carotid Artery ◽  
Rabbit Carotid Artery ◽  
Endothelium Dependent Relaxation

Role of nitric oxide and carbon monoxide in Nω-Nitro-l-arginine methyl ester-resistant acetylcholine-induced relaxation in chicken carotid artery

2008 ◽  
Vol 596 (1-3) ◽  
pp. 111-117 ◽  
Author(s):  
Marie Dennis Marcus Leo ◽  
Yeshavanth K.B. Siddegowda ◽  
Dinesh Kumar ◽  
Surendra K. Tandan ◽  
Kochiganti V.H. Sastry ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Methyl Ester ◽  
Carotid Artery

Endothelium-Dependent Relaxation of Small Arteries from Essential Hypertensive Patients: Mechanisms and Comparison with Normotensive Subjects and with Responses of Vessels from Spontaneously Hypertensive Rats

1995 ◽  
Vol 88 (6) ◽  
pp. 611-622 ◽  
Author(s):  
L-Yuan Deng ◽  
LI Jin-Sheng ◽  
Ernesto L. Schiffrin
Keyword(s):  
Nitric Oxide ◽  
Essential Hypertension ◽  
Methyl Ester ◽  
Potassium Channels ◽  
Spontaneously Hypertensive Rats ◽  
Hypertensive Rats ◽  
Hypertensive Patients ◽  
Spontaneously Hypertensive ◽  
Small Arteries ◽  
Endothelium Dependent Relaxation

1. Impaired endothelium-dependent relaxation has been previously demonstrated in blood vessels of hypertensive rats and in humans with essential hypertension. Arteries from spontaneously hypertensive rats have been shown to produce, in response to high concentrations of acetylcholine, a vasoconstrictor substance called endothelium-derived contracting factor, the production of which can be inhibited by indomethacin or other cyclo-oxygenase inhibitors, suggesting that it is a prostanoid. The mechanisms involved in endothelium-dependent relaxation of human arteries are unclear, and the potential generation of endothelium-derived contracting factor by endothelium in human hypertension has not been established. 2. We investigated the effects of acetylcholine on precontracted small arteries dissected from gluteal subcutaneous fat biopsies from normotensive subjects and subjects with borderline and mild essential hypertension. Vessels from normotensive subjects and those from borderline hypertensive patients, precontracted by noradrenaline, were relaxed completely by acetylcholine, whereas those from patients with mild essential hypertension relaxed slightly but significantly less, indicating that generation of endothelium-derived relaxing factor (endothelium-derived nitric oxide) was only minimally reduced or that production of minor amounts of endothelium-derived contracting factor occurred in small arteries from these hypertensive subjects. This impairment of endothelium-dependent relaxation was not corrected by indomethacin, which indicated that the contribution of endothelium-derived contracting factor, if any, was minimal in this subset of essential hypertensive patients. In contrast, mesenteric small arteries of adult spontaneously hypertensive rats presented strong contractions in response to the higher concentrations of acetylcholine, which were abolished by exposure to indomethacin. 3. The relaxation induced by acetylcholine in arteries from both hypertensive and normotensive humans was partially blunted (by 30%) by pretreatment with 0.1 mmol/l NG-nitro-l-arginine methyl ester or NG-nitro-monomethyl-l-arginine (inhibitors of nitric oxide synthase) and by 10 μmol/l Methylene Blue (a blocker of soluble guanylate cyclase), indicating the role of endothelium-derived nitric oxide and the generation of its intracellular second messenger cyclic guanosine monophosphate in acetylcholine-induced relaxation. The remaining relaxation elicited by acetylcholine could be blocked with 30 mmol/l KCl or with 10 μmol/l ouabain (inhibitor of Na+, K+-ATPase), and, when combined with NG-nitro-l-arginine methyl ester, these interventions abolished acetylcholine-induced relaxation. Tolbutamide at 2 mmol/l or 10 μmol/l glyburide (blockers of ATP-sensitive potassium channels) partially inhibited NG-nitro-l-arginine methyl ester-resistant endothelium-dependent relaxation. Apamin (a blocker of small-conductance calcium-activated potassium channels), which has been shown to block NG-nitro-l-arginine methyl ester-resistant endothelium-dependent relaxation in rat arteries, was without effect. Charybdotoxin (blocker of large-conductance calcium-activated potassium channels) displaced to the right the responses to acetylcholine, in the absence and presence of NG-nitro-l-arginine methyl ester and/or tolbutamide. 4. In conclusion, in contrast to mesenteric small arteries from spontaneously hypertensive rats, which produce endothelium-derived contracting factor, subcutaneous small arteries from subjects with mild essential hypertension appear not to do so in significant amounts. Thirty per cent of the relaxation induced by acetylcholine in human small arteries is mediated by release of endothelium-derived nitric oxide, whereas more than 60% is the result of release of another agent, perhaps the putative endothelium-derived hyperpolarizing factor, which may act in part by opening ATP-sensitive potassium channels and large-conductance calcium-activated potassium channels. Endothelium-dependent relaxation induced by acetylcholine was normal in borderline hypertensive subjects and only slightly abnormal in the mildly hypertensive patients studied.

Heterogeneity in role of endothelium-derived NO in pulmonary arteries and veins of full-term fetal lambs

1995 ◽  
Vol 268 (4) ◽  
pp. H1586-H1592 ◽  
Author(s):  
Y. Gao ◽  
H. Zhou ◽  
J. U. Raj
Keyword(s):  
Nitric Oxide ◽  
Isometric Force ◽  
Pulmonary Veins ◽  
Pulmonary Arteries ◽  
Full Term ◽  
Fourth Generation ◽  
Cyclic Monophosphate ◽  
Arteries And Veins ◽  
Endothelium Dependent Relaxation

Endothelium-derived nitric oxide (EDNO) modulates fetal pulmonary vasoactivity. The role of EDNO in regulation of vasomotor tone in fetal pulmonary arteries vs. that in veins is not known. We have investigated the role of EDNO in the responses of pulmonary arteries and veins of full-term fetal lambs. Fourth-generation pulmonary arterial and venous rings were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2 at 37 degrees C), and their isometric force was measured. N omega-nitro-L-arginine had no effect on the resting tension of pulmonary arteries with endothelium but caused contraction of pulmonary veins with endothelium. The basal level of intracellular guanosine 3',5'-cyclic monophosphate (cGMP) of pulmonary veins with endothelium was higher than that of arteries with endothelium. In pulmonary arteries, bradykinin, but not acetylcholine, induced endothelium-dependent relaxation and an increase in cGMP content. In pulmonary veins, acetylcholine, but not bradykinin, induced endothelium-dependent relaxation and an increase in cGMP content. Agonist-induced maximal relaxation and increases in cGMP content were smaller in pulmonary arteries than in veins. All these endothelium-dependent responses were abolished by N omega-nitro-L-arginine. In tissues without endothelium, nitric oxide induced significantly less relaxation and less increase in cGMP content in pulmonary arteries than in pulmonary veins. All vessels relaxed similarly to 8-bromoguanosine 3',5'-cyclic monophosphate. Our data suggest that the role of EDNO in modulating tone differs between pulmonary arteries and veins in full-term fetal lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of NO in goat basal cerebral circulation and after vasodilatation to hypercapnia or brief ischemias

1993 ◽  
Vol 265 (6) ◽  
pp. R1410-R1415 ◽  
Author(s):  
G. Dieguez ◽  
J. L. Garcia ◽  
N. Fernandez ◽  
A. L. Garcia-Villalon ◽  
L. Monge ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Heart Rate ◽  
Methyl Ester ◽  
Cerebral Circulation ◽  
Systemic Arterial Pressure ◽  
Nitric Oxide Production ◽  
Hemodynamic Effects ◽  
Arterial Pco2 ◽  
Different Levels

The role of nitric oxide (NO) in the cerebral circulation under basal conditions and after vasodilatation to hypercapnia or reactive hyperemias was studied in 17 anesthetized goats. The intravenous administration of NG-nitro-L-arginine methyl ester (L-NAME, 3-4 or 8-10 mg/kg), an inhibitor of nitric oxide production, reduced middle cerebral artery (MCA) flow (electromagnetically measured) by 19 and 30% and increased systemic arterial pressure by 21 and 26%, respectively, whereas heart rate did not significantly change; MCA resistance increased by 48 and 86%, respectively. These hemodynamic effects were reversed by L-arginine (200-300 mg/kg iv; 5 goats). Different levels of hypercapnia (PCO2 of 30-35, 40-45, and 55-65 mmHg) (12 goats) produced arterial PCO2-dependent increases in MCA flow that were similar under control and L-NAME treatment. Graded cerebral hyperemia occurred after 5, 10, and 20 s of MCA occlusion in 5 goats, but its magnitude was decreased during L-NAME treatment. It suggests that, in the cerebral circulation, nitric oxide 1) produces a basal vasodilator tone and 2) is probably not involved in the vasodilatation to hypercapnia but may mediate hyperemic responses after short brain ischemias.

In vivo location and mechanism of EDHF-mediated vasodilation in canine coronary microcirculation

1999 ◽  
Vol 277 (3) ◽  
pp. H1252-H1259 ◽  
Author(s):  
Yasuhiro Nishikawa ◽  
David W. Stepp ◽  
William M. Chilian
Keyword(s):  
Nitric Oxide ◽  
Potassium Channels ◽  
Potassium Channel ◽  
Direct Evidence ◽  
Coronary Microcirculation ◽  
Combined Administration ◽  
Cytochrome P 450 ◽  
Coronary Arterioles

Responses of epicardial coronary arterioles to ACh were measured using stroboscopic fluorescence microangiography in dogs ( n = 38). ACh (0.1 and 0.5 μg ⋅ kg−1 ⋅ min−1ic) dilated small (<100 μm, 11 ± 2 and 19 ± 2%, respectively) and large (>100 μm, 6 ± 3 and 13 ± 3%, respectively) arterioles at baseline. Combined administration of N ω-monomethyl-l-arginine (l-NMMA; 1.0 μmol/min ic) and indomethacin (10 mg/kg iv) eliminated ACh-induced dilation in large coronary arterioles but only partially attenuated that in small arterioles. Suffusion of a buffer containing 60 mM KCl (high KCl) completely abolished cromakalim-induced dilation in arterioles and in combination with l-NMMA plus indomethacin completely blocked ACh-induced dilation in small arterioles. This indicated that the vasodilation to ACh that persists in small arterioles after administration of l-NMMA and indomethacin is mediated via a hyperpolarizing factor. The ACh-induced vasodilation remaining after l-NMMA and indomethacin was completely blocked by the large-conductance potassium-channel antagonist iberiotoxin or by epicardial suffusion of miconazole or metyrapone, inhibitors of cytochrome P-450 enzymes. These observations are consistent with the view that endothelium-derived hyperpolarizing factor (EDHF) is a product of cytochrome P-450 enzymes and produces vasodilation by the opening of large-conductance potassium channels. We conclude that ACh-induced dilation in large coronary arterioles is mediated mainly by nitric oxide (NO), whereas, in small arterioles both NO and EDHF mediate dilation to ACh. These data provide the first direct evidence for an in vivo role of EDHF in small coronary arterioles.

Nitric oxide attenuates endothelin-1-induced vasoconstriction in canine stomach

1996 ◽  
Vol 271 (1) ◽  
pp. G27-G35
Author(s):  
J. G. Wood ◽  
Q. Zhang ◽  
Z. Y. Yan ◽  
L. Y. Cheung
Keyword(s):  
Nitric Oxide ◽  
Methyl Ester ◽  
Ischemia Reperfusion ◽  
Nitric Oxide Donor ◽  
Question Mark ◽  
Endothelin 1 ◽  
Vasoconstrictor Response ◽  
Anesthetized Dogs ◽  
Spermine Nonoate

We previously observed that endothelin-1 (ET-1)-induced gastric vasoconstriction is enhanced after ischemia-reperfusion. The purpose of our present study was to examine the role of nitric oxide in regulating ET-1-induced vasoconstriction under normal conditions and after ischemia-reperfusion. Using a mechanically perfused stomach segment from chloralose-anesthetized dogs, we examined 1) responses to NG-nitro-L-arginine methyl ester (L-NAME) alone and in combination with L-arginine, 2) whether L-NAME affects ET-1-induced vasoconstriction under normal conditions and after ischemia-reperfusion, and 3) if spermine NONOate inverted question mark1,3-propanediamine-N-[4-1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazi no] butyl; a nitric oxide donor inverted question mark attenuates the augmented response to ET-1 after ischemia-reperfusion. Our results show that 1) L-NAME significantly increased baseline vascular resistance and this response was reduced by L-arginine, 2) ET-1-induced vasoconstriction was enhanced by L-NAME, and 3) administration of spermine NONOate during reperfusion largely attenuated the vasoconstrictor response to ET-1 after ischemia-reperfusion. Our findings are consistent with the hypothesis that nitric oxide modulates responses to ET-1 under normal conditions, and loss of this vasodilator after ischemia-reperfusion results in an augmented response to ET-1.

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