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E Bassenge

Publications and source records attributed to E Bassenge.

At least 19 recordsLinked to original sources
PubMed1999

Assembly and characterization of canine heart endothelial nitric oxide synthase cDNA and 5'-flanking sequence by homology (RT-)PCR cloning.

A broad spectrum of cardiovascular diseases is studied in canine animal models, in which dysfunction or dysregulation of the endothelial nitric oxide synthase (ecNOS) is of pivotal pathogenetic importance. To provide the tools for subsequent molecular analyses of ecNOS structure or function and to identify putative regulatory factors we isolated and characterized the canine heart ecNOS cDNA and putative regulatory (promoter) sequences. The complete coding sequence, 5'- plus part of 3'-untranslated regions (UTR) of ecNOS cDNA, and part of the 5'-flanking sequence (putative promoter region) were identified by homology (RT-)PCR cloning using canine heart total RNA or genomic DNA. Primer sequences were derived from bovine/human ecNOS cDNAs or genes. An ecNOS sequence contig of 5138 nucleotides length was established containing an open reading frame of 3618 nucleotides (1206 amino acids predicting a 133-kDa protein) and 253 bp 3'-UTR (distal to TGA codon)/1267 bp proximal to ATG codon (containing 5'-UTR and 5'-flanking sequences = putative promoter region). Comparison to human, bovine, murine, or porcine ecNOS sequences at the nucleotide or amino acid level yielded between 86 and 91% or 83 and 84% homologies, respectively. The canine ecNOS 5'-flanking sequence (putative promoter region) revealed stretches of homology up to 86% as compared to the human sequence containing a cluster of binding sites for several regulatory elements. The homology (RT-)PCR cloning strategy is presented as an alternative to common library cloning approaches. The obtained canine ecNOS sequence might serve to further analyze the structure, regulated function (promoter region consensus sites), and expression of ecNOS in different pathophysiological conditions and in other species (GenBank Accession No. BankIt264069 AF143503).

Amino Acid Sequence↗
PubMed1999

Comparison of glyceryl trinitrate-induced with pentaerythrityl tetranitrate-induced in vivo formation of superoxide radicals: effect of vitamin C.

Glyceryl trinitrate (GTN) and pentaerythrityl tetranitrate (PETN) are among the most known organic nitrates that are used in cardiovascular therapy as vasodilators. However, anti-ischemic therapy with organic nitrates is complicated by the induction of nitrate tolerance. When nitrates are metabolized to release nitric oxide (NO), there is considerable coproduction of superoxide radicals in vessels leading to inactivation of NO. However, nitrate-induced increase of superoxide radical formation in vivo has not been reported. In this work, the authors studied the in vivo formation of superoxide radicals induced by treatment with PETN or GTN and determined the antioxidant effect of vitamin C. The formation of superoxide radicals was determined by the oxidation of 1-hydroxy-3-carboxy-pyrrolidine (CP-H) to paramagnetic 3-carboxy-proxyl (CP) using electron spin resonance spectroscopy. CP-H (9 mg/kg intravenous bolus and 0.225 mg/kg per minute continuous intravenous GTN or PETN 130 microg/kg) were infused into anesthetized rabbits. Every 5 min, blood samples were obtained from Arteria carotis to measure the CP formation. Both PETN and GTN showed similar vasodilator effects. Formation of CP in blood after infusions of GTN and PETN were 2.0+/-0.4 microM and 0.98+/-0.23 microM, respectively. Pretreatment with 30 mg/kg vitamin C led to a significant decrease in CP formation: 0.27+/-0.14 microM (vitamin C plus GTN) and 0.34+/-0.15 microM (vitamin C plus PETN). Pretreatment of animals with superoxide dismutase (15,000 units/kg) significantly inhibited nitrate-induced nitroxide formation. Therefore, in vivo infusion of GTN or PETN in rabbits increased the formation of superoxide radicals in the vasculature. PETN provoked a minimal stimulation of superoxide radical formation without simultaneous development of nitrate tolerance. The data suggest that the formation of superoxide radicals induced by organic nitrate correlates with the development of nitrate tolerance. The effect of vitamin C on CP formation leads to the conclusion that vitamin C can be used as an effective antioxidant for protection against nitrate-induced superoxide radical formation in vivo.

Animals↗
PubMed1998

Detection of superoxide radicals and peroxynitrite by 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine: quantification of extracellular superoxide radicals formation.

The reactions of the new sterically hindered hydroxylamine 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine (PP-H) with superoxide radical and peroxynitrite have been studied. These reactions produce the nitroxide 4-phosphonooxy-2,2,6, 6-tetramethyl-piperidinyloxy. The rate constant for reaction of superoxide with PP-H is determined as (8.4+/-0.6).10(2) M-1s-1. It was found that PP-H provides almost the same spin trapping efficacy as 1-hydroxy-3-carboxy-pyrrolidine (CP-H). The background oxidation of PP-H in blood is much less than for CP-H. The extremely slow PP-H penetration into the cells makes possible the study of extracellular formation of superoxide radical. The acute treatment of blood with nitroglycerin is shown to induce an extracellular superoxide radical formation. PP-H is more sensitive for detection of reactive oxygen species as compared with CP-H. PP-H is an effective scavenger of superoxide radical and of peroxynitrite, and can be used to quantify the extracellular formation of these reactive oxygen species.

Electron Spin Resonance Spectroscopy↗
PubMed1998

Dietary supplement with vitamin C prevents nitrate tolerance.

Enhanced formation of superoxide radicals has been proposed to play a major role in the development of nitrate tolerance in humans. We tested the effects of vitamin C (Vit-C) supplementation on glyceroltrinitrate (GTN)-induced hemodynamic effects during 3-d nonintermittent transdermal administration of GTN (0.4 mg/h) in nine healthy subjects. Tolerance development was monitored by changes in arterial pressure, dicrotic digital pulse pressure, and heart rate. Studies with GTN, Vit-C, or GTN/Vit-C were successively carried out at random in three different series in the same subjects. GTN treatment caused an immediate rise in arterial conductivity (a/b ratio of dicrotic pulse), but within 2 d of initiating GTN, the a/b ratio progressively decreased and reached basal levels. In addition, there was a progressive loss of the orthostatic decrease in blood pressure. However, coadministration of Vit-C and GTN fully maintained the GTN-induced changes in the orthostatic blood pressure, and the rise of a/b ratio was augmented by 310% for the duration of the test period. Changes in vascular tolerance in GTN-treated subjects were paralleled by upregulation of the activity of isolated platelets, which was also reversed by Vit-C administration. These findings demonstrate that dietary supplementation with Vit-C eliminates vascular tolerance and concomitant upregulation of ex vivo-washed platelet activity during long-term nonintermittent administration of GTN in humans.

Adult↗
PubMed1998

Venous Function in Patients with Venous Disease and Healthy Controls Before and After a Bathing Procedure and Subsequent Cold Stimulus

The object of this study was to determine whether bathing in thermal water acutely affects venous function in patients with venous insufficiency. Measurements were taken of venous function in patients with leg varicosities and healthy subjects before and after a thermal bath and exercise on two days, with subsequent application of a cold stimulus on 1 day. A total of 28 patients with varicose veins in one or both legs (n = 45 legs) and 30 healthy controls (n = 60 legs). On 2 consecutive days all subjects underwent a standardized bathing and exercise procedure in water at 34 degreesC for 20 minutes. On one day, determined randomly for each subject, a cold stimulus was applied to both lower legs after bathing. Measurements were done before subjects entered the bath and after the completion of bathing (including cold stimulus on one day). Without the cold stimulus, venous function of patients and controls did not change. After application of the cold stimulus the venous capacity of both patients and controls was significantly reduced compared with the basal levels. There was no change in maximum venous outflow in the controls, but that of the patient group decreased slightly compared with basal levels. Contrary to widespread belief, bathing in water at temperatures above 28 degreesC does not adversely affect venous function in patients with varicose veins. When applied in moderation (34 degreesC for 20 minutes) this physical therapy should not be regarded as contraindicated in this and related conditions, especially given its known hemodynamic benefits. Further studies are required to determine the long-term effects of repeated immersion.

Journal Article↗
PubMed1998

Intrinsic neural regulation of the heart in the chronic, conscious dog.

The present experiments were performed to examine the capability of the intrinsic cardiac nerves (ICN) to modify cardiac performance in the resting chronic, conscious dog. Control and cardiac-denervated dogs were instrumented for recording of left atrial (LA) and ventricular (LV) contractility, heart rate, and atrioventricular (AV) conduction time. Acetylcholine (ACh) and nicotine (Nic) were administered via an indwelling coronary artery catheter. Limited distribution from the injection site only allowed access to the LA, LV, and AV node. Both beta-blockade with timolol and cardiac denervation were used to separate direct effects of ICN stimulation from indirect (e.g., reflex) effects. ACh produced the expected negative inotropic and dromotropic changes. ICN stimulation with Nic caused large decreases in LA on but only trivial effects on the LV. We concluded that the ICN has limited effects on cardiac performance in the resting animal under minimal sympathetic drive. It is likely, however, that the ICN is capable of significantly depressing cardiac function under conditions of elevated sympathetic tone as would be encountered in exercise.

Acetylcholine↗
PubMed1998

Formation of reactive oxygen species by pentaerithrityltetranitrate and glyceryl trinitrate in vitro and development of nitrate tolerance.

Anti-ischemic therapy with organic nitrates is complicated by tolerance. Induction of tolerance is incompletely understood and likely multifactorial. Recently, increased production of reactive oxygen species (ROS) has been investigated, but it has not been clear if this is a direct consequence of the organic nitrate on the vessel or an in vivo adaptation to the drugs. To examine the possibility that nitrates could directly stimulate vascular ROS production, we compared the development of nitrate tolerance with the formation of ROS induced by pentaerithrityltetranitrate (PETN) or nitroglycerin (GTN) in vitro in porcine smooth muscle cells, endothelial cells, washed ex vivo platelets and whole blood. By examining cGMP formation, it was found that 24-hr treatment with GTN but not PETN induced significant nitrate tolerance, which was prevented by parallel treatment with Vit C. Incubation of vascular cells acutely with 0.5 mM GTN doubled the rate of ROS generation, whereas PETN had no such effect. The rate of ROS (peroxynitrite and O2) formation detected by specific spin traps in tolerant smooth muscle cells, treated for 24 hr with 0.01 mM GTN, was substantially higher (30.5 nM/min) than in control cells acutely treated with 0.5 mM GTN (25 nM/min). In contrast to PETN, GTN induces nitrate tolerance and also increases the formation of ROS both in vascular cells and in whole blood. ROS formation is minimally stimulated by PETN comparable to data obtained in Vit C-suppressed GTN tolerance. ROS formation induced by organic nitrates seems to be a key factor in the development of nitrate tolerance.

Animals↗
PubMed1997

Spin trapping of superoxide radicals and peroxynitrite by 1-hydroxy-3-carboxy-pyrrolidine and 1-hydroxy-2,2,6, 6-tetramethyl-4-oxo-piperidine and the stability of corresponding nitroxyl radicals towards biological reductants.

The reactions of new spin trap 1-hydroxy-3-carboxy-pyrrolidine (CP-H) with superoxide radicals and peroxynitrite were studied. The rate constants were determined as 3.2 x 10(3) and 4.5 x 10(9) M-1s-1, respectively. It was found that 2mM of spin trap CP-H or 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine (TEMPONE-H) provide almost the same spin trapping efficacy. In contrast to TEMPONE-H the reaction of CP-H with peroxynitrite was inhibited by 20 mM DMSO. This simplifies the quantification of peroxynitrite formation. During the reaction of CP-H and TEMPONE-H with superoxide radicals or peroxynitrite the stable nitroxide radicals 3-carboxy-proxyl (CP) and 2,2,6,6-tetramethyl-4-oxo-piperidinoxyl (TEMPONE) are formed. It was found that the rate of reduction of CP by glutathione or by smooth muscle cells was two-fold slower and the reduction of CP by ascorbate was 66-fold slower than corresponding rates of reduction of TEMPONE. Therefore quantification of the formation of superoxide radicals and of peroxynitrite by CP-H is much less hindered by a variety of biological reductants than in case of TEMPONE-H. Thus, CP-H is more suitable for spin trapping of superoxide radicals and peroxynitrite in biological systems than the TEMPONE-H.

Animals↗
PubMed1997

Quantification of peroxynitrite, superoxide, and peroxyl radicals by a new spin trap hydroxylamine 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine.

The reactions of hydroxylamine 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine hydrochloride (TEMPONE-H) with peroxynitrite, superoxide and peroxyl radicals were studied. It was shown that under these reactions TEMPONE-H is oxidized into a stable nitroxide 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidi-noxyl (TEMPONE). The reactivity of TEMPONE-H towards reactive oxygen species was compared with the spin traps DMPO and TMIO as well as with DMSO and SOD. The rate constants of reactions of TEMPONE-H with peroxynitrite and superoxide radicals were 6 x 10(9) M(-1)s(-1) and 1.2x10(4) M(-1)s(-1), respectively. Using TEMPONE-H the sensitivity in the detection of peroxynitrite or superoxide radical was about 10-fold higher than using the spin traps DMPO or TMIO. Thus, TEMPONE-H may be used as a spin trap in chemical and biological systems to quantify peroxynitrite and superoxide radical formation.

Amidines↗
PubMed1997

Quantification of superoxide radicals and peroxynitrite in vascular cells using oxidation of sterically hindered hydroxylamines and electron spin resonance.

The reactions of two hydroxylamines, 1-hydroxy-3-carboxy-pyrrolidine (CP-H) and 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine (TEMPONE-H), with superoxide radicals and peroxynitrite were studied. In these reactions corresponding stable nitroxyl radicals 3-carboxy-proxyl (CP) and 1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinoxyl (TEMPONE) are formed and the amount of them can be quantified by electron spin resonance (ESR). It was found that CP-H and TEMPONE-H provide almost the same efficacy in assaying peroxynitrite by ESR in vitro at pH 7.4. The formation of superoxide radicals in suspensions of cells was discriminated from that of peroxynitrite using superoxide dismutase or dimethyl sulfoxide as competitive reagents. The stability of the radicals CP and TEMPONE in the presence of ascorbate or thiols was studied in vitro. The reduction rate of CP by ascorbate was 66-fold slower than the rate of reduction of TEMPONE. Therefore, the quantification of the formation of superoxide radicals and of peroxynitrite is much less affected by ascorbic acid when CP-H, but not TEMPONE-H, is used. Both TEMPONE-H and CP-H were used to determine the formation rates of superoxide radicals and peroxynitrite in suspensions of cultured aortic smooth muscle cells and endothelial cells, in washed ex vivo platelets, and in blood treated with glycerol trinitrate (GTN) as an NO donor. It was shown that both the acute addition of GTN (0.5 mM) to vascular cells and the incubation of smooth muscle or endothelial cells in culture with 0.1 mM GTN for 24 h enhance significantly the formation of reactive oxygen species in cells. The rates of of superoxide radical formation were increased at least in two times and peroxynitrite was detected. Hydroxylamines TEMPONE-H and CP-H can be used as nontoxic compounds in ESR assay capable of quantifying the formation of superoxide radicals and peroxynitrite in suspensions of cells and in the whole blood with high sensitivity.

Analysis of Variance↗
PubMed1997

Unexpected, tolerance-devoid vasomotor and platelet actions of pentaerythrityl tetranitrate.

Efficacy of nitrate therapy is limited by tolerance. A surprising upregulation of ex vivo platelet activity, a decrease in platelet thiol levels, and an enhanced release of vasoconstrictors from platelets is associated with enhanced superoxide-mediated oxidant stress leading to vascular tolerance to nitrates. We tested the NO-donor pentaerythrityl tetranitrate (PETN), which to date had not been precisely tested either with regard to the induction of tolerance or to a potential development of changes in platelet activity in comparison with glycerol trinitrate (GTN). Long-term instrumented dogs nonintermittently received: 1.5 microg/kg/min GTN, i.v., with or without vitamin C (55 microg/kg/min, i.v.) or PETN 4 x 60 mg/day orally for 5 days. Tested daily were (a) the dilation of the epicardial arteries, (b) thrombin-induced (0.5 U/ml) increases of the intracellular Ca2+ concentration and aggregability of platelets, (c) concentrations of reduced low-molecular-weight thiols (LMTs) in plasma and platelets, and (d) formation of reactive oxygen species (ROSs). During nonintermittent PETN and during GTN with additional vitamin C, a 9.8 +/- 0.4% coronary artery dilation was observed in contrast to that with GTN alone, which resulted in complete tolerance at day 4. This vascular tolerance was associated with enhanced platelet activity and formation of ROSs (incubated platelets) and a 38 +/- 3% reduction in LMT. These unfavorable changes were absent in the presence of PETN or with additional vitamin C as an antioxidant. Vascular tolerance associated with platelet upregulation is avoided either by nonintermittent nitroglycerin (5 days) when vitamin C is coadministered or by pentaerythrityl tetranitrate without the coadministration of vitamin C.

Animals↗
PubMed1997

Effect of carbon dioxide-enriched water and fresh water on the cutaneous microcirculation and oxygen tension in the skin of the foot.

The effects of immersion of the lower leg and foot in fresh water and in carbon dioxide (CO2)-enriched water (1200 mg CO2 per kg water; succinate+sodium bicarbonate: Actibath, KAO Tokyo) on cutaneous circulation, vasomotion and oxygen tension (PO2) were measured by laser Doppler flowmetry and transcutaneous oximetry. On the first of two consecutive days patients were randomly assigned to have the lower extremities immersed in either fresh water or CO2-enriched water under standardized conditions (temperature, 34 degrees C; depth, 35 cm; immersion time, twenty minutes) with concurrent measurement. On the second day patients were switched to the other bath type. For both sets of measurements probes were attached symmetrically to the dorsum of each foot. Included in the study were 18 patients with mild, bilateral, peripheral, occlusive arterial disease (intermittent claudication, femoral or iliac type). During immersion in CO2-enriched water the Doppler laser signal and vasomotion amplitude rose by 300%, while PO2 increased by 10%. These increases were still apparent during the latter part of the measurement period, following withdrawal of the limbs from the bath, while patients were seated and supine. During immersion in fresh water and thereafter the Doppler laser signal was unchanged and the PO2 increase was considerably less marked. The authors were thus able to demonstrate vasodilation and increased oxygen utilization (Bohr effect) resulting from topical CO2 application, and hence, that the use of topical CO2 has an objective basis.

Aged↗
PubMed1997

Effects of serial percutaneous application of carbon dioxide in intermittent claudication: results of a controlled trial.

In a prospective, controlled clinical trial, serial application of carbon-dioxide-enriched water was compared with fresh water. Twenty-four patients with peripheral arterial occlusive disease (stable claudication) were randomly allocated to one of two serial intervention groups, lower extremities immersed in either fresh water or in CO2-enriched water (1000 mg CO2/kg) water under standardized conditions (temperature, 33 degrees C; depth, 40 cm; immersion time, 30 min; five times a week over 4 weeks). The serial application of carbon-dioxide-enriched water increased arterial peak flow (reactive hyperemia), transcutaneous oxygen tension (basal value and half-recovery-time), and pain-free walking distance. The serial fresh water application did not change these values. The authors conclude that serial carbon dioxide application can be clinically effective in patients with arterial obstructions in the lower extremities.

Adult↗
PubMed1996

EPR and laser flash photolysis studies of the reaction of nitric oxide with water soluble NO trap Fe(II)-proline-dithiocarbamate complex.

Diethyl-dithiocarbamate (DETC) chelating ferrous iron is used during EPR detection of nitric oxide (.NO) as a precursor of spin traps for the quantification of released .NO both in vitro and in vivo. This method is based on the high affinity of water insoluble iron-dithiocarbamate complexes towards .NO. The nitrosyl-iron-dithiocarbamate complex NOFe(DETC)2 is formed with characteristic triplet EPR spectrum. In the present paper we have studied the reaction of water soluble Fe(II)-proline-dithiocarbamate complex, Fe(PDTC)2, with nitric oxide using both EPR spectroscopy and laser flash photolysis. It has been found that the treatment of the Fe(PDTC)2 complex either by authentic .NO dissolved in aqua buffer solutions or by different .NO donors results in the quantitative appearance of an EPR signal of a stable mononitrosyl complex NOFe(PDTC)2 with a g-factor giso = 2.04 and a hyperfine splitting constant aN = 12.5 G. The laser flash photolysis method has been used to study the kinetics of .NO trapping by Fe(PDTC)2. Nitric oxide release from a light sensitive .NO donor, piridazinofuroxan, was induced by a short flash of UV light generated by a XeCl eximer laser. The rate constant of the reaction of .NO with Fe(PDTC)2 was found to be (1.1 +/- 0.3).10(8) M-1s-1, manifesting a high efficiency of .NO trapping by Fe(PDTC)2.

Electron Spin Resonance Spectroscopy↗
PubMed1996

Long-term angiotensin-converting enzyme inhibition with high-dose enalapril retards nitrate tolerance in large epicardial arteries and prevents rebound coronary vasoconstriction in vivo.

BACKGROUND: Rebound myocardial ischemia develops in patients with unstable or stable angina pectoris after sudden cessation of nitroglycerin therapy. Long-term nitroglycerin infusion is associated with increases in plasma renin activity and catecholamine release rates, both of which may lead to excess angiotensin II and alpha-adrenergic-mediated vasoconstriction, particularly on withdrawal of nitroglycerin. METHODS AND RESULTS: Chronically instrumented dogs were treated for 5 days with nitroglycerin (1.5 micrograms.kg-1.min-1 i.v.) alone or in combination with the angiotensin-converting enzyme (ACE) inhibitor enalapril (0.1 mg/kg two times daily or 1 mg/kg). With long-term nitroglycerin therapy, the left anterior circumflex artery was maximally dilated 4 hours after the start of nitroglycerin infusion (9.5 +/- 0.6%) and returned to baseline levels within the third day of treatment (baseline, 2.52 +/- 0.07 mm; day 3, 2.55 +/- 0.07 mm; P = NS), indicating a complete loss of nitroglycerin-induced coronary vasodilatation. Nitroglycerin infusion also was accompanied by a transient increase in plasma renin activity. Sudden withdrawal of nitroglycerin infusion caused a progressive constriction of the left anterior circumflex artery, which peaked 4 hours after nitroglycerin infusion cessation (-7.8 +/- 0.2%). This occurred in the absence of elevated plasma renin activity. Concomitant treatment with high-dose enalapril (1 mg.kg-1.d-1) markedly reduced the degree of tolerance and prevented the rebound constriction on cessation of nitroglycerin therapy. CONCLUSIONS: Long-term ACE inhibition with high-dose enalapril reduces nitroglycerin tolerance and prevents rebound vasoconstriction in coronary arteries. These phenomena were not associated with an activated circulating renin-angiotensin system. This observation suggests that during long-term nitroglycerin treatment, intrinsic abnormalities of the vascular smooth muscle may have developed that are suppressed by concomitant ACE inhibitor therapy. The present study also favors a combination of nitroglycerin and ACE inhibitors to maintain nitrate sensitivity of the vasculature during long-term nitroglycerin treatment.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Tolerance to nitrates and simultaneous upregulation of platelet activity prevented by enhancing antioxidant state.

We analysed the induction of tolerance to nitrates both in the vasculature (in vivo) and platelets (ex vivo). Simultaneously, we tested mechanisms underlying the induction of tolerance and interventions to prevent or overcome this phenomenon. For this purpose nitroglycerin (GTN 1.5 micrograms/kg per min i.v.), alone or in combination with ascorbate (55 micrograms/kg per min i.v.) as antioxidant, was infused continuously for a period of 5 days into chronically instrumented dogs. Along with haemodynamic parameters, ex vivo platelet function was continuously monitored. Following the start of GTN infusions there was a maximal coronary dilator response (245 +/- 15 microm) and, as an index of venodilation, a fall of left ventricular end-diastolic pressure (by 2.3 +/- 0.4 mmHg). Both responses declined progressively and disappeared during the infusion period. However, in combination with ascorbate as antioxidant the dilator responses were maintained fully throughout the infusion period. With GTN alone there was a progressive, unexpected upregulation of platelet activity demonstrated by enhanced thrombin-stimulated intracellular Ca2+ levels and increases in the microviscosity of platelet membranes (indicating enhanced receptor expression) associated with a progressive impairment in basal, unstimulated cGMP levels. These changes could also be prevented completely by i.v. co-administration of ascorbate. From these results it is concluded that vascular tolerance is closely reflected by simultaneous changes in platelet function and further, that both can be prevented completely by appropriate antioxidants such as ascorbate.

Animals↗
PubMed1995

In vivo spin trapping of glyceryl trinitrate-derived nitric oxide in rabbit blood vessels and organs.

BACKGROUND: The objectives of this study were (1) to assess glyceryl trinitrate (GTN)-derived nitric oxide (NO) formation in vascular tissues and organs of anesthetized rabbits in vivo, (2) to establish a correlation between tissue NO levels and a biological response, and (3) to verify biotransformation of GTN to NO by cytochrome P-450. METHODS AND RESULTS: NO was trapped in tissues in vivo as a stable paramagnetic mononitrosyl-iron-diethyldithiocarbamate complex [NOFe(DETC)2]. After removal of the tissues, NO was determined by cryogenic electron spin resonance spectroscopy. NO formation in vitro was assessed by spin trapping and by activation of soluble guanylyl cyclase. The GTN-elicited decrease in coronary perfusion pressure was monitored in isolated, constant-flow perfused rabbit hearts. NO was not detected in control tissues. In GTN-treated rabbits, NO formation was higher in organs than in vascular tissues and higher in venous than in arterial vessels. In isolated hearts, ventricular NO levels and decreases in coronary perfusion pressure achieved by GTN were closely correlated. Purified cytochrome P-450 catalyzed NO formation from GTN in a P-450-NADPH reductase- and NADPH-dependent fashion. CONCLUSIONS: Since GTN-derived NO formation in myocardial tissue correlates to the GTN-elicited vasodilator response, we conclude that GTN-derived NO detected in vivo correlates with the systemic effects of GTN. Therefore, the higher rate of NO formation detected in veins compared with arteries explains the preferential venodilator activity of GTN. High NO formation in cytochrome P-450-rich organs in vivo and efficient NO formation from GTN by cytochrome P-450 in vitro highlights the importance of this pathway for NO formation from GTN in the intact organism.

Animals↗