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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Experiments were designed to determine whether endothelial cell injury contributes to increased coronary vascular tone after global cardiac ischemia and reperfusion. Canine hearts were exposed to global ischemia for 45 minutes and were reperfused for 60 minutes. Rings (5 to 6 mm long) of the left anterior descending coronary artery from reperfused hearts and from normal (control) hearts were suspended for isometric force measurement in organ chambers containing physiologic salt solution (37 degrees C, and 95% oxygen and 5% carbon dioxide). After contraction with prostaglandin F2 alpha, reperfused coronary arteries had significant impairment of endothelium-dependent relaxations to aggregating platelets (52% +/- 12% relaxation versus 102% +/- 11% for control segments; p less than 0.05). Reperfused arterial rings also exhibited impaired endothelium-dependent relaxations to the receptor-dependent agonist acetylcholine and the platelet-derived compounds adenosine diphosphate and serotonin. Importantly, endothelium-dependent relaxations to the non-receptor-dependent agonist A23187 were normal after ischemia and reperfusion. Quiescent (noncontracted) reperfused arterial rings lost the ability to counteract the constrictive effect of aggregating platelets on the coronary vascular smooth muscle (24% +/- 7% contraction versus 5% +/- 2% relaxation for control segments; p less than 0.05). Endothelium-independent contractions to potassium chloride and prostaglandin F2 alpha were similar in reperfused and normal arteries. Also, endothelium-independent relaxations to nitric oxide and isoproterenol were comparable in reperfused arteries and normal vessels. Thus global cardiac ischemia and reperfusion impair the normal endothelium-dependent relaxations to aggregating platelets and other receptor-dependent vasoactive drugs. This impairment of platelet-mediated coronary vasodilation may explain increased coronary vascular tone after cardiopulmonary bypass and could be an important pathophysiologic mechanism of postoperative coronary vasospasm.
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PMID:Global myocardial ischemia and reperfusion impair endothelium-dependent relaxations to aggregating platelets in the canine coronary artery. A possible cause of vasospasm after cardiopulmonary bypass. 159 79

Electrocorticographic (ECoG) activity remains isoelectric for about 15 min after transient (10 min) bilateral carotid arteries occlusion in mongolian gerbils. In this model of global forebrain ischemia N omega-Nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, significantly delays the recovery of ECoG amplitude. Thus, the present experiments suggest that NO is involved in the cerebrovascular physiological response to brain ischemia.
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PMID:N omega-nitro-L-arginine-methyl ester inhibits electrocortical recovery subsequent to transient global brain ischemia in Mongolian gerbil. 160 27

Nitric oxide (NO) and prostacyclin (PGI2) release was determined in effluents of Langendorff-perfused rabbit hearts under control conditions and during reperfusion subsequent to 2 h of global, low-flow ischemia. PGI2 release (6-oxo-PGF1 alpha) was significantly enhanced during early reperfusion and remained enhanced during a total time of 70 min of reperfusion. NO formation was reduced during ischemia but was substantially enhanced during reperfusion. Inhibition of endogenous PGI2 production by indomethacin resulted in severe disturbance of myocardial function and NO release. Inhibition of NO generation by L-N-nitroarginine did not affect myocardial contractility. These data suggest a cardioprotective and endothelium-protective role of PGI2 in myocardial ischemia which also involves protection of NO generation.
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PMID:Endogenous prostacyclin preserves myocardial function and endothelium-derived nitric oxide formation in myocardial ischemia. 163 6

Fetal ischemia or hypoxia can lead to cerebral palsy, mental retardation and epilepsy. We propose that the production of nitric oxide and oxygen radicals by neurons when ischemic or hypoxic brain is reperfused may contribute to cerebral injury. Ischemia will depolarize neuronal membranes causing the synaptic discharge of the excitatory neurotransmitter glutamate, which in turn opens the voltage-dependent, N-methyl-D-aspartic acid-specific glutamate receptor/ionophore, allowing calcium to accumulate in the neuron. Calcium in turn activates an oxygen-dependent neuronal nitric oxide synthetase, which oxidizes arginine to produce nitric oxide (.NO) when oxygen is readmitted to brain by reperfusion. Nitric oxide reacts with the oxygen radical superoxide (O2-), also produced by reperfusion, to form peroxynitrite (ONOO-). Peroxynitrite can diffuse for several micrometers before decomposing to form the powerful and cytotoxic oxidants hydroxyl radical and nitrogen dioxide. The hypothesis is consistent with available evidence on the protective action of glutamate antagonists and of oxygen radical scavengers for limiting cerebral infarction following focal ischemia.
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PMID:The double-edged role of nitric oxide in brain function and superoxide-mediated injury. 167 55

Experiments were carried out to provide evidence of the effect of L-arginine (L-Arg), its analogue NG-monomethyl-L-arginine (MeArg) and of some nitrovasodilators (sodium nitroprusside, NaNP; 3-morpholino-sydnonimine, SIN-1) which spontaneously release nitric oxide (NO) on ischemia-reperfusion injury, histamine release and mast cell degranulation, occurring after multiple ligature and release of the left anterior descending (LAD) coronary artery in isolated perfused guinea-pig hearts. The reopening of the LAD coronary artery leads to a release of histamine related to a decrease in microdensitometry of cardiac mast cells and to calcium overload. The perfusion of the heart with NO-donors significantly reduces either the release of histamine, the loss of mast cell metachromasia and the overload of calcium. These effects were potentiated by SOD. The results suggest that the endogenous formation of NO and molecules able to generate NO have a role in the prevention of post-ischemic tissue injury.
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PMID:The effect of nitric oxide generators on ischemia reperfusion injury and histamine release in isolated perfused guinea-pig heart. 171 36

In an ischemia-reperfusion model obtained in isolated perfused guinea pig heart by means of a double ligature of the left anterior descending coronary artery, the reperfusion of the ischemic myocardium leads to a release of lactate dehydrogenase and histamine, related to a decrease in the microdensitometry of cardiac mast cells and to a tissue calcium overload. The perfusion of the heart with L-arginine and with nitric oxide donors significantly reduces the release of histamine, the loss of mast cell metachromasia and calcium overload. These effects were potentiated by superoxide dismutase.
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PMID:Effect of nitric oxide generators on ischemia-reperfusion injury and histamine release in isolated perfused guinea pig heart. 171 88

Endothelium-dependent relaxation of conductance coronary vessels involves nitric oxide formation from L-arginine. The present study examines whether a similar mechanism intervenes in the vasomotor control of resistance coronary vessels. In conscious dogs, the excess of coronary blood flow (CBF) created by intracoronary acetylcholine (3.0 ng/kg) averaged 7.2 +/- 1.1 ml. Intracoronary adenosine (100 ng/kg) increased CBF by 12.4 +/- 1.4 ml. Intracoronary nitroglycerin (175 ng/kg) increased CBF by 7.4 +/- 1.2 ml. CBF repayment-to-debt ratio after a 15-s coronary arterial occlusion averaged 2.8 +/- 0.2. After an intracoronary N omega-nitro-L-arginine dose (10 micrograms.kg-1.min-1 x 12 min) was given to inhibit nitric oxide formation, baseline CBF was not altered. CBF increases with acetylcholine averaged 2.4 +/- 0.5 and 6.4 +/- 0.7 ml with adenosine, both less (P less than 0.01) than responses before the arginine analogue. CBF increases with nitroglycerin averaged 7.2 +/- 1.1 ml, similar to control responses. CBF repayment-to-debt ratio during reactive hyperemic responses fell (P less than 0.01) to 1.7 +/- 0.1. L-Arginine (1.0 mg.kg-1.min-1 x 12 min) partially reversed the inhibitory effect of the arginine analogue on CBF responses to acetylcholine. Thus nitric oxide formed in resistance coronary vessels is a major mediator of coronary vasodilation to acetylcholine, adenosine and transient ischemia.
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PMID:Contribution of nitric oxide to dilation of resistance coronary vessels in conscious dogs. 173 2

The interaction of platelets with the vessel wall plays an important pathophysiological role in coronary artery disease. While in healthy blood vessels platelets remain inactivated and do not adhere or aggregate, an augmented interaction occurs in coronary artery disease. Due to their strategic anatomical position between the circulating blood and the media of the vascular wall, endothelial cells play an important regulatory role. Indeed, after endothelial denudation, massive platelet adhesion and aggregation at the vessel wall occurs. Platelet-derived substances lead to vasoconstriction and in the long run also to proliferative changes of the vascular wall. Besides other substances, endothelial cells release vasoactive mediators such as endothelium-derived nitric oxide (NO), prostacyclin and endothelin. In healthy human arteries, aggregating platelets cause endothelium-dependent relaxations in spite of the liberation of serotonin and thromboxane A2 and through the luminally released NO also induce a feedback inhibition of the platelets. In contrast, in arteries without endothelium, a marked vasoconstriction (due to thromboxane A2 and serotonin) is noted. Endothelin may also play a role in platelet-vessel wall interaction, since thrombin and transforming growth factor beta (a platelet-derived product) stimulate the production of this potent vasoconstrictor. Oxidized low-density lipoproteins inhibit the relase of NO and thereby activate the platelet-vessel wall interaction. In atherosclerosis even more pronounced dysfunctions of the endothelium occur, which lead to vasoconstriction, ischemia and thrombus formation in patients with coronary artery disease.
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PMID:[Thrombocyte-vascular wall interaction and coronary heart disease]. 176

Oxygen metabolites have been reported to produce vasoconstriction and/or vasodilation in a variety of in vitro or in vivo vascular preparations. Certain basic mechanisms appear to contribute to these responses. Hydrogen peroxide can produce either vasodilation or constriction via stimulation of prostaglandins. The soluble form of guanylate cyclase in vascular smooth muscle, an enzyme which produces the intracellular mediator of relaxation cyclic GMP, is also a site of action of vasoactive O2 metabolites. Guanylate cyclase is directly activated by nanomolar concentrations of nitric oxide (produced by endothelial cells or nitrovasodilator drugs) or H2O2 (via its metabolism by catalase). These cyclic GMP-mediated mechanisms of relaxation are inhibited by superoxide anion, produced from endogenous sources after inhibition of superoxide dismutase or produced by pharmacological agents that undergo redox cycling. In addition, O2 metabolites may modulate vascular tone via the chemical destruction of physiological contractile agents (e.g. norepinephrine) and relaxant agents (e.g. nitric oxide), and via injury to cells important for the regulation of vascular tone (e.g. endothelium). We have found in a variety of preparations that reexposure to O2 after a brief period of severe hypoxia produces vascular responses that appear to be mediated by intracellular H2O2 generation. Thus, active O2 species may contribute to vascular responses in pathophysiological situations associated with their formation (e.g. inflammation, ischemia/reperfusion, etc.) and to the physiological regulation of vascular tone produced by changes in O2 tension (e.g. reactive hyperemia, hypoxic vasoconstriction, etc).
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PMID:Activated oxygen metabolites as regulators of vascular tone. 179 78

To determine whether coronary reperfusion enhances the production of endothelium-derived contracting factor, we investigated dogs subjected to global cardiac ischemia (45 minutes) followed by reperfusion (60 minutes). Segments of reperfused and control coronary arteries were suspended in organ chambers to measure isometric force. Perfusate hypoxia caused endothelium-dependent contraction in the control and reperfused arteries. However, reperfused arteries exhibited hypoxic contraction that was significantly greater than control segments. The hypoxic contractions in both the control and reperfused arteries could be inhibited by NG-monomethyl-L-arginine (L-NMMA), the blocker of endothelial cell synthesis of nitric oxide from L-arginine. The action of L-NMMA could be reversed by L-arginine but not D-arginine. Thus, after reperfusion, augmented production of endothelium-derived contracting factor occurs by an L-arginine-dependent pathway. We hypothesize that nitric oxide produced by L-arginine metabolism combines with superoxide anion to produce the peroxynitrite anion (ONOO-), which is metabolized to endothelium-derived contracting factor or induces its synthesis. Augmented production of endothelium-derived contracting factor would favor vasospasm after reperfusion.
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PMID:Production of endothelium-derived contracting factor is enhanced after coronary reperfusion. 190 53


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