Nitric oxide-induced vasodilation of organic nitrate-tolerant rabbit aorta

1988 ◽  
Vol 66 (10) ◽  
pp. 1344-1346 ◽  
Author(s):  
Christopher J. Slack ◽  
Brian E. McLaughlin ◽  
Kanji Nakatsu ◽  
Gerald S. Marks ◽  
James F. Brien
Keyword(s):  
Nitric Oxide ◽  
Glyceryl Trinitrate ◽  
Isosorbide Dinitrate ◽  
Vascular Tissue ◽  
Rabbit Aorta ◽  
Nitrate Tolerance ◽  
Organic Nitrate ◽  
Vasodilator Agents ◽  
Vasodilator Drugs ◽  
Before And After

It is postulated that the organic nitrate vasodilator agents, including glyceryl trinitrate (GTN) and isosorbide dinitrate (ISDN), are prodrugs, such that biotransformation to the active inorganic metabolite, nitric oxide (NO), occurs prior to the onset of vasodilation. Furthermore, it is proposed that organic nitrate tolerance in vascular tissue involves decreased formation of NO. To test this latter hypothesis, we examined vasodilation induced by NO, GTN, and ISDN in non-tolerant, GTN-tolerant, and ISDN-tolerant rabbit aortic rings (RARs). Isolated RARs were contracted submaximally with phenylephrine; the time of onset of relaxation and percent relaxation of tissue were determined in response to NO (0.3 μM), GTN (0.03 μM), and ISDN (0.12 μM) before and after a 1-h treatment with 500 μM GTN, 500 μM ISDN, or buffer only. The data demonstrated that the response to NO was not changed in GTN-tolerant and ISDN-tolerant tissues, in which there was virtually no GTN-induced or ISDN-induced relaxation. These results are consistent with the postulate that organic nitrate vasodilator drugs must undergo biotransformation to NO before vasodilation can occur and that the mechanism of organic nitrate tolerance involves decreased formation of NO.

Biotransformation of glyceryl trinitrate by rat brain homogenate

1992 ◽  
Vol 70 (6) ◽  
pp. 935-937 ◽  
Author(s):  
Gerald S. Marks ◽  
Brian E. McLaughlin ◽  
Kanji Nakatsu ◽  
James F. Brien
Keyword(s):  
Nitric Oxide ◽  
Glyceryl Trinitrate ◽  
Rat Brain ◽  
Brain Homogenate ◽  
Organic Nitrate ◽  
Oxide Formation ◽  
Anaerobic Conditions ◽  
Nitric Oxide Formation ◽  
Selective Formation ◽  
Vasodilator Drug

Incubation of glyceryl trinitrate (GTN) with 5% (w/v) rat brain homogenate (RBH) resulted in biotransformation of the organic nitrate vasodilator drug to a mixture of glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN). Heating of the RBH at 100 °C for 5 min and (or) pretreatment with 5 mM N-ethylmaleimide at 37 °C for 10 min demonstrated that about two-thirds of the GTN biotransformation activity was due to a sulfhydryl-dependent enzymatic process resulting in the predominant formation of 1,2-GDN, and that the remaining biotransformation activity was due to a sulfhydryl-dependent nonenzymatic process resulting in the selective formation of 1,3-GDN. In a preliminary experiment, nitric oxide formation was observed during the incubation of GTN with RBH under anaerobic conditions. These data support the idea that some of the therapeutic and adverse effects of GTN are mediated through its action in the central nervous system.Key words: glyceryl trinitrate, biotransformation, rat brain homogenate, sulfhydryl-dependent enzyme, nitric oxide formation.

Effect of temperature on glyceryl trinitrate induced relaxation of rabbit aorta

1993 ◽  
Vol 71 (8) ◽  
pp. 629-632 ◽  
Author(s):  
Brian P. Booth ◽  
James F. Brien ◽  
Gerald S. Marks ◽  
Kanji Nakatsu
Keyword(s):  
Nitric Oxide ◽  
Cardiopulmonary Bypass ◽  
Glyceryl Trinitrate ◽  
Rabbit Aorta ◽  
Tissue Response ◽  
Effect Of Temperature ◽  
Hypothermic Cardiopulmonary Bypass ◽  
Reduced Body ◽  
Vasodilatory Response ◽  
Two Temperatures

It has previously been shown that the vasodilatory response to glyceryl trinitrate (GTN) was decreased during hypothermic cardiopulmonary bypass. The purpose of these experiments was to determine the effect of temperature on GTN-induced relaxation and on GTN biotransformation in rabbit aorta. It was determined that the EC50 of GTN on rabbit aortic rings (RARs) was increased significantly from 1.8 × 10−8 M at 37 °C to 3.4 × 10−8 M at 27 °C (p < 0.05). The production of NO by rabbit aortic strips (RASs) was significantly less at 27 °C compared with 37 °C after 80 min, being 9.62 × 10−11 ± 13.2 × 10−11 mol NO/g wet wt. RASs compared with 5.71 × 10−10 ± 9.43 × 10−11 mol NO/g wet wt. RASs, respectively (p < 0.05), after 80 min incubation. There was no difference in the amount of glyceryl-1,2-dinitrate (1,2-GDN) produced from GTN at the two temperatures. The ED20 for NO-induced relaxation of RARs increased from 3.46 × 10−10 ± 2.24 × 10−10 mol at 37 °C to 1.01 × 10−9 ± 4.51 × 10−10 mol at 27 °C (p < 0.05). These data indicate that the biotransformation of GTN and the release of NO were impaired by hypothermia, and that this, as well as a decrease in the tissue response to NO at 27 °C, explains the decrease in GTN activity at reduced body temperatures.Key words: glyceryl trinitrate, nitric oxide, temperature, rabbit aorta, vasodilation.

Effect of in vivo nitrate tolerance on hypersensitivity to NO donors after NO-synthase blockade

2002 ◽  
Vol 80 (11) ◽  
pp. 1106-1118 ◽  
Author(s):  
Jodan D Ratz ◽  
Michael A Adams ◽  
Brian M Bennett
Keyword(s):  
Nitric Oxide ◽  
Glyceryl Trinitrate ◽  
Nitrate Tolerance ◽  
Metabolite Formation ◽  
No Donor ◽  
No Donors ◽  
Nos Inhibitors ◽  
Pressure Lowering ◽  
Oxide Synthase

Animals treated with nitric oxide synthase (NOS) inhibitors exhibit marked hypersensitivity to the blood pressure lowering effects of exogenous nitric oxide (NO) donors. We used this model as a sensitive index to evaluate the relative importance of reduced biotransformation of glyceryl trinitrate (GTN) to NO in the development of nitrate tolerance. NOS-blockade hypertension using NG-nitro-L-arginine methyl ester (L-NAME) caused a marked enhancement of the mean arterial pressure (MAP) decrease mediated by GTN in nontolerant rats. However, even large doses of GTN were unable to change the MAP in GTN-tolerant, NOS-blockade hypertensive animals. In contrast, the MAP responses to the spontaneous NO donor sodium nitroprusside (SNP) were completely unaltered in either tolerant rats or tolerant NOS-blockade hypertensive animals, indicating that NO-dependent vasodilatory mechanisms remain intact despite the development of GTN tolerance. The MAP-lowering effects of GTN in NOS-blockade hypertensive animals were restored 48 h after cessation of chronic GTN exposure. These alterations in the pharmacodynamic response to GTN during tolerance development and reversal were associated with parallel changes in the pattern of GTN metabolite formation, suggesting that the activity of one or more enzymes involved in nitrate metabolism was altered as a consequence of chronic GTN exposure. These findings suggest that the vasodilation resulting from the vascular biotransformation of GTN to NO (or a closely related species) is severely compromised in nitrate-tolerant animals, and that although other mechanisms may contribute to the vascular changes observed following the development of GTN tolerance, decreased GTN bioactivation is likely the most important.Key words: biotransformation, glyceryl trinitrate, hypertension, nitric oxide, tolerance.

Inhibition of nitrovasodilators by pyocyanin and methylene blue is dissociated from nitric oxide formation

1994 ◽  
Vol 72 (7) ◽  
pp. 746-752 ◽  
Author(s):  
Jovan Bozinovski ◽  
James F. Brien ◽  
Gerald S. Marks ◽  
Kanji Nakatsu
Keyword(s):  
Nitric Oxide ◽  
Methylene Blue ◽  
Sodium Nitroprusside ◽  
Isosorbide Dinitrate ◽  
Rabbit Aorta ◽  
Aortic Ring ◽  
Organic Nitrates ◽  
No Production ◽  
Nitric Oxide Formation ◽  
No Formation

The phenazine pigment pyocyanin (Pyo), like methylene blue (MB), inhibits vascular relaxation induced by organic nitrates. These nitrovasodilators are pro-drugs that have in common the ability to generate nitric oxide (NO). In this study, we characterized responses of rabbit isolated aortic ring to 3-morpholinosydnonimine (SIN-1), S-nitroso-N-acetylpenicillamine (SNAP), sodium nitroprusside, glyceryl trinitrate (GTN), and isosorbide dinitrate in the presence and absence of 10 μM Pyo. We also examined the effect of Pyo (1 and 10 μM) and MB (1 and 10 μM) on vasorelaxation induced by authentic NO, and finally we tested the effects of Pyo and MB on the tissue-independent formation of NO from SIN-1, SNAP, and sodium nitroprusside, using die chemiluminescence – headspace gas method. Pyo (10 μM) surmountably inhibited aortic responses to GTN, isosorbide dinitrate, SIN-1, and SNAP with a characteristic rightward shift of the dose–response curve; the apparent EC50 of these drugs for relaxation of phenylephrine-contracted aorta was increased 18-, 4-, 13-, and 15-fold, respectively. Pyo (1 and 10 μM) and MB (10 μM) inhibited NO-induced vasorelaxation at the EC50 of NO by 35, 72, and 56%. In contrast, Pyo did not inhibit sodium nitroprusside induced vasodilation. For a 10-min incubation, 10 μM Pyo or MB increased NO production from SNAP 1.8- and 2.9-fold, respectively, and increased NO production from SIN-1 by 3.8- and 7.1-fold, respectively. Neither Pyo nor MB enhanced NO formation from sodium nitroprusside. These data indicate that Pyo and MB inhibit nitrovasodilator-induced relaxation of aortic ring by interfering with the action of NO, subsequent to its formation.Key words: pyocyanin, nitric oxide, methylene blue, nitrovasodilators, rabbit aorta.

Role of peroxynitrite in altered fetal-placental vascular reactivity in diabetes or preeclampsia

2000 ◽  
Vol 278 (4) ◽  
pp. H1311-H1319 ◽  
Author(s):  
Wilhelm Kossenjans ◽  
Annie Eis ◽  
Rashmi Sahay ◽  
Diane Brockman ◽  
Leslie Myatt
Keyword(s):  
Oxidative Stress ◽  
Nitric Oxide ◽  
Glyceryl Trinitrate ◽  
Human Placenta ◽  
Vascular Reactivity ◽  
Vascular Dysfunction ◽  
Ang Ii ◽  
Vascular Responses ◽  
Before And After

Oxidative stress may increase production of superoxide and nitric oxide, leading to formation of prooxidant peroxynitrite to cause vascular dysfunction. Having found nitrotyrosine residues, a marker of peroxynitrite action, in placental vessels of preeclamptic and diabetic pregnancies, we determined whether vasoreactivity is altered in these placentas and treatment with peroxynitrite produces vascular dysfunction. The responses of diabetic, preeclamptic, and normal placentas to increasing concentrations of the vasoconstrictors U-46619 (10− 9–10− 7M) and ANG II (10− 9–10− 7M) and the vasodilators glyceryl trinitrate (10− 9–10− 7M) and prostacyclin (PGI2; 10− 8–10− 6M) were compared as were responses to these agents in normal placentas before and after treatment with 3.16 × 10− 4 M peroxynitrite for 30 min. Responses to both vasoconstrictors and vasodilators were significantly attenuated in diabetic and preeclamptic placentas compared with controls. Similarly, responses to U-46619, nitroglycerin, and PGI2, but not ANG II, were significantly attenuated following peroxynitrite treatment. The presence of nitrotyrosine residues confirmed peroxynitrite interaction with placental vessels. Overall, our data suggest that peroxynitrite formation is capable of attenuating vascular responses in the human placenta.

Nitric oxide formation from glyceryl trinitrate in the developing guinea-pig hippocampus

2000 ◽  
Vol 12 (6) ◽  
pp. 245 ◽  
Author(s):  
Adrian C. Crowe ◽  
Malcolm E. Chang ◽  
Brian E. McLaughlin ◽  
James F. Brien
Keyword(s):  
Nitric Oxide ◽  
Guinea Pig ◽  
Glyceryl Trinitrate ◽  
Life Time ◽  
Organic Nitrate ◽  
Postnatal Life ◽  
No Donor ◽  
Aerobic Conditions ◽  
No Formation ◽  
Pharmacologic Effect

Glyceryl trinitrate (GTN) is classified as an organic nitrate vasodilator drug. GTN is considered to be a prodrug because it undergoes biotransformation at its site of action to form nitric oxide (NO) or a NO adduct, which produces its pharmacologic effect. The objectives of this study were to determine whether the hippocampus can biotransform GTN to NO using aerobic conditions, and whether biotransformation of GTN to NO is age-dependent during postnatal life. Time-dependent formation of NO occurred during the incubation of 100 µM GTN with 2.5% (w/v) homogenate of guinea-pig hippocampus at 37°C using aerobic conditions. GTN-derived NO formation was similar in magnitude for the three selected postnatal ages that were studied, that is, postnatal days 10, 20 and > 60. The data demonstrate that the capacity of the hippocampus for NO formation from GTN is fully developed in the guinea-pig in early postnatal life. In view of these findings, it is conceivable that a NO donor drug, selectively metabolized to NO in the hippocampus, could be a useful therapeutic intervention to mitigate structural and/or functional defects in this brain region resulting from decreased NO formation or availability.

Effects of Hypoxia–Reoxygenation on Microvascular Endothelial Function in the Rat Hippocampal Slice 

1999 ◽  
Vol 91 (5) ◽  
pp. 1462-1462 ◽  
Author(s):  
Michael Staunton ◽  
Cathy Drexler ◽  
Michael G. Dulitz ◽  
Dale C. Ekbom ◽  
William T. Schmeling ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Endothelial Function ◽  
Sodium Nitroprusside ◽  
Rat Brain ◽  
Vascular Tissue ◽  
Brain Slices ◽  
Before And After ◽  
Cerebral Arterioles ◽  
Hypoxia Reoxygenation

Background Cerebral ischemia and hypoxia may cause injury to both neuronal and vascular tissue. The direct effects of hypoxia on endothelial function in intraparenchymal cerebral arterioles are unknown. Using a modification of the rat brain slice preparation, allowing continuous imaging of these previously inaccessible vessels, microvessel dilation was evaluated before and after a brief hypoxic episode. Methods Rat brain slices were superfused with oxygenated artificial cerebrospinal fluid. Hippocampal arterioles were visualized using computerized videomicroscopy, and their diameters (range, 12-27 microm) were measured using image analysis. After preconstriction with prostaglandin F2alpha and controlled pH and carbon dioxide tension, graded concentrations of either acetylcholine (endothelium-dependent vasodilation) or sodium nitroprusside (endothelium-independent vasodilation) were given before and after a 10-min period of hypoxia. Results Sodium nitroprusside (100 microM) caused similar dilation before and after hypoxia (mean +/- SEM: 9.6 +/- 0.6% vs. 13.0 +/- 0.9%). Acetylcholine (100 microM) caused significantly less dilation (P &lt; 0.05) after hypoxia (mean +/- SEM: 9.3 +/- 1.8% vs. 3.6 +/- 1.2%). The decreased acetylcholine-induced dilation after hypoxia was not reversed by pretreatment with L-arginine (1 mM), the precursor of nitric oxide (mean +/- SEM: 8.8 +/- 1.3% vs. 4.4 +/- 0.7%). Conclusions Even brief periods of hypoxia may cause endothelial dysfunction in intraparenchymal cerebral arterioles. This does not seem to be related to a deficiency of the nitric oxide substrate, L-arginine. Endothelial dysfunction and impaired endothelium-dependent dilation of microvessels may decrease oxygen delivery and increase neuronal injury during cerebral hypoxia-reoxygenation.

Biotransformation of glyceryl trinitrate and isosorbide dinitrate in vascular smooth muscle made tolerant to organic nitrates

1989 ◽  
Vol 67 (11) ◽  
pp. 1381-1385 ◽  
Author(s):  
Christopher J. Slack ◽  
Brian E. McLaughlin ◽  
James F. Brien ◽  
Gerald S. Marks ◽  
Kanji Nakatsu
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Glyceryl Trinitrate ◽  
Isosorbide Dinitrate ◽  
Isosorbide Mononitrate ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Nitrate Anion ◽  
Pharmacologically Active

It has been proposed that organic nitrates are prodrugs and biotransformation to a pharmacologically active metabolite (i.e., nitric oxide) must occur before the onset of vasodilation. If this postulated mechanism is correct, tolerance to organic nitrate-induced vasodilation might involve decreased biotransformation of organic nitrates by vascular smooth muscle. In this study, biotransformation of isosorbide dinitrate (ISDN) and glyceryl trinitrate (GTN) was estimated by measuring isosorbide mononitrate (ISMN) and glyceryl dinitrate (GDN), respectively, rather than the nitrate anion, because of a more sensitive method for measurement of ISMN and GDN. To test this hypothesis, isolated rabbit aortic strips (RAS) were made tolerant in vitro by incubation with 500 μM GTN or ISDN for 1 h. After a washout period and submaximal contraction with phenylephrine, the tissues were incubated with either 2.0 μM [14C]ISDN or 0.5 μM [14C]GTN for 2 min. ISDN- or GTN-induced relaxation of RAS was monitored and tissue parent drug and metabolite contents were determined by thin-layer chromatography and liquid scintillation spectrometry. ISDN- and GTN-induced relaxation of RAS and the metabolite concentrations were significantly less for both GTN- and ISDN-tolerant tissue compared with nontolerant tissue. These results are consistent with the hypothesis that organic nitrate biotransformation is required for organic nitrate-induced vasodilation.Key words: organic nitrates, glyceryl trinitrate, isosorbide dinitrate, biotransformation, prodrug, tolerance.

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