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M S Wolin

Publications and source records attributed to M S Wolin.

At least 37 records · Page 2Linked to original sources
PubMed1999

NO modulates myocardial O2 consumption in the nonhuman primate: an additional mechanism of action of amlodipine.

Recent evidence from our laboratory and others suggests that nitric oxide (NO) is a modulator of in vivo and in vitro oxygen consumption in the murine and canine heart. Therefore, the goal of our study was twofold: to determine whether NO modulates myocardial oxygen consumption in the nonhuman primate heart in vitro and to evaluate whether the seemingly cardioprotective actions of amlodipine may involve an NO-mediated mechanism. Using a Clark-type O2 electrode, we measured oxygen consumption in cynomologous monkey heart at baseline and after increasing doses of S-nitroso-N-acetylpenicillamine (SNAP; 10(-7)-10(-4) M), bradykinin (10(-7)-10(-4) M), ramiprilat (10(-7)-10(-4) M), and amlodipine (10(-7)-10(-5) M). SNAP (-38 +/- 5.8%), bradykinin (-19 +/- 3.9%), ramiprilat (-28 +/- 2.3%), and amlodipine (-23 +/- 4.5%) each caused significant (P < 0.05) reductions in myocardial oxygen consumption at their highest dose. Preincubation of tissue with nitro-L-arginine methyl ester (10(-4) M) blunted the effects of bradykinin (-5.4 +/- 3.2%), ramiprilat (-4.8 +/- 5.0%), and amlodipine (-5.3 +/- 5.0%) but had no effect on the tissue response to SNAP (-38 +/- 5.8%). Our results indicate that NO can reduce oxygen consumption in the primate myocardium in vitro, and they support a role for the calcium-channel blocker amlodipine as a modulator of myocardial oxygen consumption via a kinin-NO mediated mechanism.

Amlodipine↗
PubMed1999

Inhibition of guanylate cyclase stimulation by NO and bovine arterial relaxation to peroxynitrite and H2O2.

The inhibitor of soluble guanylate cyclase (sGC) stimulation by nitric oxide (NO), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), was examined for its effects on the prolonged relaxation of endothelium-removed bovine coronary (BCA) and pulmonary (BPA) arteries to peroxynitrite (ONOO-) and on H2O2-elicited relaxation and sGC stimulation. Our previous studies suggest that ONOO- causes a prolonged relaxation of BPA by regenerating NO and that a 2-min exposure of BCA or BPA to 50 nM NO causes an ONOO--elicited relaxation. The relaxation of K+-precontracted BCA to 50 nM NO or 100 microM ONOO- was essentially eliminated by 10 microM ODQ. ODQ also eliminated relaxation to 0.1 nM-10 microM of NO donor S-nitroso-N-acetyl-penicillamine (SNAP), but it did not alter relaxation to 1-300 microM H2O2. Similar responses were also observed in BPA. ODQ did not increase lucigenin-detectable superoxide production in BCA, and it did not alter luminol-detectable endogenous ONOO- formation observed during a 2-min exposure of BCA to 50 nM NO. In addition, ODQ did not affect tissue release of NO after 2 min exposure of BCA to 50 nM NO. The activity of sGC in BPA homogenate that is stimulated by endogenous H2O2 was not altered by ODQ, whereas sGC activity in the presence of 10 microM SNAP (+fungal catalase) was reduced by ODQ. Thus relaxation of K+-precontracted BCA and BPA to ONOO- appears to be completely mediated by NO stimulation of sGC, whereas the actions of ODQ suggest that NO is not involved in H2O2-elicited relaxation and sGC stimulation. This study did not detect evidence for the participation of additional mechanisms potentially activated by ONOO- in the responses studied.

Animals↗
PubMed1999

NADPH and heme redox modulate pulmonary artery relaxation and guanylate cyclase activation by NO.

The hemoprotein oxidant ferricyanide (FeCN) converts the iron of the heme on soluble guanylate cyclase (sGC) from Fe(2+) to Fe(3+), which prevents nitric oxide (NO) from binding the heme and stimulating sGC activity. This study uses FeCN to examine whether modulation of the redox status of the heme on sGC influences the relaxation of endothelium-removed bovine pulmonary arteries (BPA) to NO. Pretreatment of the homogenate of BPA with 50 microM FeCN resulted in a loss of stimulation of sGC activity by the NO donor 10 microM S-nitroso-N-acetylpenicillamine (SNAP). In the FeCN-treated homogenate reconcentrated to the enzyme levels in BPA, 100 microM NADPH restored NO stimulation of sGC, and this effect of NADPH was prevented by an inhibitor of flavoprotein electron transport, 1 microM diphenyliodonium (DPI). In BPA the relaxation to SNAP was not altered by FeCN, inhibitors of NADPH generation by the pentose phosphate pathway [250 microM 6-aminonicotinamide (6-AN) and 100 microM epiandrosterone (Epi)], or 1 microM DPI. However, the combination of FeCN with 6-AN, Epi, or DPI inhibited (P < 0.05) relaxation to SNAP without significantly altering the relaxation of BPA to forskolin. The inhibitory effects of 1 microM 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalin-1-one (a probe that appears to convert NO-heme of sGC to its Fe(3+)-heme form) on relaxation to SNAP were also enhanced by DPI. These observations suggest that a flavoprotein containing NADPH oxidoreductase may influence cGMP-mediated relaxation of BPA to NO by maintaining the heme of sGC in its Fe(2+) oxidation state.

Animals↗
PubMed1998

S-Nitroglutathione, a product of the reaction between peroxynitrite and glutathione that generates nitric oxide.

Peroxynitrite (ONOO-) has been shown in studies on vascular relaxation and guanylate cyclase activation to react with glutathione (GSH), generating an intermediate product that promotes a time-dependent production of nitric oxide (NO). In this study, reactions of ONOO- with GSH produced a new substance, which was characterized by liquid chromatography, ultraviolet spectroscopy, and electrospray tandem mass spectrometry. The mass spectrometric data provided evidence that the product of this reaction was S-nitroglutathione (GSNO2) and that S-nitrosoglutathione (GSNO) was not a detectable product of this reaction. Further evidence was obtained by comparison of the spectral and chromatographic properties with synthetic standards prepared by reaction of GSH with nitrosonium or nitronium borofluorates. Both the synthetic and ONOO-/GSH-derived GSNO2 generated a protonated ion, GSNO2H+, at m/z 353, which was unusually resistant to decomposition under collision activation, and no fragmentation was observed at collision energy of 25 eV. In contrast, an ion at m/z 337 (GSNOH+), generated from the synthetic GSNO, readily fragmented with the abundant loss of NO at 9 eV. Reactions of ONOO- with GSH resulted in the generation of NO, which was detected by the head space/NO-chemiluminescence analyzer method. The generation of NO was inhibited by the presence of glucose and/or CO2 in the buffers employed. Synthetic GSNO2 spontaneously generated NO in a manner that was not significantly altered by glucose or CO2. Thus, ONOO- reacts with GSH to form GSNO2, and GSNO2 decomposes in a manner that generates NO.

Chromatography, High Pressure Liquid↗
PubMed1998

Inhibition of rat cardiac muscle contraction and mitochondrial respiration by endogenous peroxynitrite formation during posthypoxic reoxygenation.

This study was designed to investigate the potential role of endogenous peroxynitrite (ONOO-) formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation. Isometric contraction of isolated rat left ventricular posterior papillary muscle was virtually eliminated at the end of an exposure to 15 minutes of hypoxia and remained 40+/-5% depressed an hour after the reintroduction of O2. O2 uptake by rat left ventricular cardiac muscle, measured by a Clark-type O2 electrode, was also inhibited by 24+/-2% at 10 minutes after reoxygenation. The inhibition of contractility and respiration during posthypoxic reoxygenation was markedly attenuated by the NO synthase inhibitor nitro-L-arginine, exogenous superoxide dismutase, and the ONOO- scavenger urate but not by the hydroxyl radical scavenger mannitol. Generation of ONOO- with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) plus the superoxide-releasing agent pyrogallol caused an irreversible inhibition of cardiac contractile and respiratory function. Unlike ONOO-, exogenous (SNAP) and endogenous (bradykinin) sources of NO inhibited contractility in a reversible manner. Under conditions of comparable amounts of respiratory inhibition in unstimulated incubated muscle, the NO-dependent agents and the mitochondrial antagonist NaCN produced a smaller degree of suppression of contractility compared with ONOO- and posthypoxic reoxygenation. These results are consistent with a contributing role for endogenous ONOO- formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation.

Animals↗
PubMed1998

Oxidant--nitric oxide signalling mechanisms in vascular tissue.

Nitric oxide has several signalling mechanisms that can potentially control force generation by vascular smooth muscle. Some of these mechanisms include the stimulation of cGMP production by the soluble heme-containing form of guanylate cyclase (sGC), inhibition of mitochondrial respiration, and the modulation of vasoactive mediator release by the endothelium. Reactive O2 species (ROS) can also regulate force generation by vascular smooth muscle through mechanisms including the stimulation of production of vasoactive prostaglandins, the stimulation of sGC by catalase-mediated metabolism of H2O2 and inhibition of sGC activation by superoxide, the activation of protein kinase C, and the modulation of mediator release from the endothelium. Interactions between NO and ROS signalling mechanisms result in additional processes which modulate vascular force generation. For example, NO-elicited stimulation of sGC can be attenuated by superoxide, and this results in the formation of peroxynitrite (ONOO-). However, high levels of NO result in a ONOO- and thiol dependent formation of a species which regenerates NO in a time-dependent manner. It appears that NO inhibits catalase through an O2 and superoxide dependent process which results in inhibition of relaxation mediated by H2O2-elicited stimulation of sGC. Furthermore, evidence exists suggesting additional signalling mechanisms resulting from interactions between regulatory systems involving NO and ROS which appear to be important in control of vascular force generation in pathophysiological states.

Animals↗
PubMed1997

Lactate and PO2 modulate superoxide anion production in bovine cardiac myocytes: potential role of NADH oxidase.

BACKGROUND: Lactate increases lucigenin chemiluminescence (CL)-detectable superoxide anion (O2.-) generation in bovine vascular smooth muscle and endothelium, and a microsomal flavoprotein-containing NADH oxidase whose activity is regulated by PO2 and cytosolic NAD(H) redox appears to be the detected source of O2.- production. Little is known about the importance of this O2.(-)-producing system in cardiac myocytes. METHODS AND RESULTS: In isolated bovine cardiac myocytes, lactate (10 mmol/L) increased lucigenin-detectable O2.- levels to approximately 1.8 times baseline, whereas pyruvate (10 mmol/L) and mitochondrial probes did not increase the detection of O2.-. A nonmitochondrial NADH oxidase activity, found in microsomes containing a cytochrome b558, was a major source of O2.- production in the homogenate of myocytes, because NADH (0.1 mmol/L) increased basal lucigenin CL >100-fold. NADPH oxidases, mitochondria, and xanthine oxidase were minor sources of detectable O2.- production. However, mitochondria released H2O2 in the presence of 5 mmol/L succinate and 30 micromol/L antimycin, based on its detection as catalase-inhibitable luminol (+horseradish peroxidase)-elicited CL. Diphenyliodonium (DPI), an inhibitor of flavoprotein-containing oxidases, significantly attenuated basal, lactate, and NADH-elicited lucigenin CL. Hypoxia eliminated myocyte lucigenin CL, and posthypoxic reoxygenation caused an 8.6-fold increase in the detection of O2.- that was potentiated by lactate and inhibited by DPI. CONCLUSIONS: NADH oxidase activity linked to cytosolic NAD(H) redox appears to be a key source of O2.- production in cardiac myocytes that could contribute to oxidant signaling mechanisms and injury upon exposure to changes in PO2 and metabolites produced under hypoxia, such as lactate. These processes could contribute to the previously observed potentiation of injury caused by lactate in cardiac ischemia/reperfusion.

Animals↗
PubMed1997

ACE inhibitors promote nitric oxide accumulation to modulate myocardial oxygen consumption.

BACKGROUND: ACE inhibitors potentiate kinin-nitric oxide (NO)-dependent coronary vascular dilation, and NO can modulate myocardial oxygen consumption. Whether ACE inhibitors also affect myocardial O2 consumption has not been established. METHODS AND RESULTS: Production of nitrite, a metabolite of NO in aqueous solution, in coronary microvessels and O2 consumption in myocardium were quantified with the use of in vitro tissue preparations, the Greiss reaction, and a Clark-type O2 electrode. In coronary microvessels, kininogen (the precursor of kinin; 10 micrograms/mL) and three ACE inhibitors (captopril, enalaprilat, or ramiprilat; 10(-8) mol/L) increased nitrite production from 76 +/- 6 to 173 +/- 15, 123 +/- 12, 125 +/- 12, and 153 +/- 12 pmol/mg, respectively (all P < .05). In myocardium, kininogen (10 micrograms/mL) and captopril, enalaprilat, or ramiprilat (10(-4) mol/L) reduced cardiac O2 consumption by 41 +/- 2%, 19 +/- 3%, 25 +/- 2%, and 35 +/- 2%, respectively. The changes in both nitrite release and O2 consumption in vitro were blocked by N omega-nitro-L-arginine methyl ester or N omega-nitro-L-arginine, inhibitors of endogenous NO formation. The effects were also blocked by HOE 140, which blocks the bradykinin B2-kinin receptor, and serine protease inhibitors, which inhibit local kinin formation. CONCLUSIONS: Our data indicate that stimulation of local kinin formation by use of a precursor for kinin formation or inhibition of kinin degradation by use of ACE inhibitors increases NO formation and is important in the control of cardiac O2 consumption. Vasodilation and control of myocardial O2 consumption by NO may contribute importantly to the therapeutic actions of ACE inhibitors in cardiac disease states.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Endogenous peroxynitrite generation causes a subsequent suppression of coronary arterial contraction to serotonin.

High levels of exogenous peroxynitrite (ONOO-) have been reported to cause coronary vascular relaxation by a mechanism that appears to involve the subsequent generation of nitric oxide (NO). In this study, we examined if endogenous vasoactive levels of ONOO are formed from endogenous superoxide anion (O2-.) upon exposure of isolated endothelium-removed bovine coronary arteries (BCA) to biological levels of NO. During exposure of BCA to approximately 50 nM NO for 2 min, the level of endogenous O2-. detected by lucigenin-dependent chemiluminescence (CL) was markedly decreased and an increase in luminol-dependent CL was observed, consistent with the detection of ONOO generation. NO treatment caused a decrease in contraction of BCA to 0.1-3 microM serotonin (5-HT). This suppression of contraction to 5-HT was completely prevented by preincubation prior to NO exposure with agents that prevent endogenous O2-. production (10 microM diphenyliodonium) or trap intracellular O2-. (10 mM Tiron) or ONOO (0.1 mM urate), and by post-NO treatment with an agent that traps NO (1 microM oxyhemoglobin) or prevents the stimulation of cGMP production by NO (10 microM methylene blue). The NO treatment caused a subsequent release of NO (measured in the head space after a 5-min equilibration with 95% N2-5% CO2), and this subsequent release of NO was reduced by the presence of urate during NO exposure and by depletion of endogenous tissue glutathione (by pretreatment with 7 mM diethyl maleate). Thus, exposure of BCA to elevated physiological levels of NO causes a prolonged suppression of contraction to 5-HT which appears to result from endogenous ONOO formation and a thiol-dependent process that traps and subsequently releases vascular relaxant levels of NO.

Animals↗
PubMed1997

NO elicits prolonged relaxation of bovine pulmonary arteries via endogenous peroxynitrite generation.

We previously reported that acute exposure of endothelium-removed bovine pulmonary arteries (BPA) to high levels (0.1 mM) of peroxynitrite (ONOO-) caused a prolonged guanosine 3',5'-cyclic monophosphate-related relaxation that appeared to be mediated through a thiol-dependent generation of nitric oxide (NO). In this study, we examined the importance of endogenous ONOO- formation in the regulation of BPA force generation by elevated physiological levels of NO. Exposure of BPA precontracted with 30 mM KCl to approximately 50 nM NO for 2 min caused a subsequent prolonged relaxation of KCl-induced force and an increased release of NO (measured in head space gas after a 5-min deoxygenation with 95% N2-5% CO2). This subsequent release of NO was reduced after depletion of tissue glutathione with diethyl maleate (DEM). Also, the NO-elicited prolonged relaxation of BPA was reversed by post-NO treatment with 10 microM methylene blue (MB; which inhibits guanylate cyclase stimulation by NO) or 1 microM oxyhemoglobin (which traps NO). Furthermore, inhibiting the biosynthesis of endogenous superoxide anion (O2-.) with 1 microM diphenyliodonium (DPI) or scavenging O2-. with 10 mM Tiron also promoted reversal of the NO-elicited prolonged relaxation seen in BPA after NO gas exposure. During exposure of BPA smooth muscle to approximately 50 nM NO gas, there appears to be a marked increase in ONOO- formation as detected by a DPI- and Tiron-inhibitable prominent increase in luminol-dependent chemiluminescence and a decrease in O2-. levels as detected by a reduction in lucigenin-dependent chemiluminescence during exposure to NO. Thus, during exposure to elevated physiological levels of NO, BPA appear to produce ONOO-, a species that seems to participate in prolonging the initial relaxation to NO through a thiol-dependent trapping and/or regeneration of NO.

Animals↗
PubMed1997

Evidence against a cytochrome P450-derived reactive oxygen species as the mediator of the nitric oxide-independent vasodilator effect of bradykinin in the perfused heart of the rat.

The coronary vasodilator effect of bradykinin (BK) in the rat is independent of NO but dependent on activation of phospholipases with involvement of cytochrome P450 mono-oxygenase (P450) and stimulation of Ca++-activated K+ channels, implicating an unidentified hyperpolarizing factor generated via P450 metabolism of arachidonic acid (AA). Because P450 activity also generates free radicals, such as superoxide, which can lead to the formation of hydrogen peroxide and hydroxyl radicals, which are vasoactive, we addressed the contribution of superoxide to the vasodilator effect of BK in the rat heart. Using rat renal microsomes as a source of P450, we verified that P450-dependent metabolism of AA generated superoxide, as detected by chemiluminescence with lucigenin. The signal was almost abolished by inhibition of P450 with clotrimazole and the superoxide scavenger 4,5-dihydroxy-1,3-benzene sulfonic acid. However, base-line superoxide formation, detected by chemiluminescence, in cardiac slices and perfused hearts was unchanged in response to BK or AA. Furthermore, in perfused hearts treated with nitroarginine and indomethacin to eliminate NO and prostaglandins and elevate perfusion pressure, dose-dependent vasodilator responses to BK were unaffected by superoxide dismutase plus catalase, a combination that abolished dilator responses to hydrogen peroxide. Similarly, the superoxide scavengers 4,5-dihydroxy-1,3-benzene sulfonic acid and 4-hydroxy-2,2,6,6-tetramethylpiperidine-noxyl were without effect on vasodilator responses to BK. Thus, the coronary vasodilator action of BK is independent of superoxide or its derivatives, which can be excluded as hyperpolarizing factors mediating NO-independent vasodilation in the rat.

Animals↗
PubMed1997

Defective endogenous nitric oxide-mediated modulation of cellular respiration in canine skeletal muscle after the development of heart failure.

BACKGROUND: It is well documented that nitric oxide (NO) suppresses the function of a number of mitochondrial enzymes. Our recent studies found that endogenous NO may play an important role in the modulation of tissue oxygen (O2) consumption and cellular respiration both in vitro and in vivo. METHODS: Tissue O2 consumption was measured by a Clark-type O2 electrode at 37 degrees C in freshly isolated skeletal muscle segments from the accessory head of the triceps brachii (90% type I muscle fiber) and extensor carpi radialis (86% type II muscle fiber) from normal dogs and dogs with tachycardia-induced heart failure. RESULTS: S-nitroso-N-acetylpenicillamine (SNAP), carbachol, and bradykinin at doses of 10(-7) to 10(-4) mol/L concentration significantly suppressed tissue O2 consumption both in the absence and presence of 2,4-dinitrophenol (1 mmol/L), a mitochondrial uncoupler. These effects were not significantly different in the accessory head of the triceps brachii (90% type I muscle fiber) and extensor carpi radialis (86% type II muscle fiber). The effects of carbachol and bradykinin but not SNAP were attenuated by NG-nitro-L-arginine (10(-4) mol/L), indicating inhibition of the formation of endogenous NO. The inhibitory effect on tissue O2 consumption in response to carbachol and bradykinin became significantly smaller in skeletal muscle from dogs with pacing-induced heart failure, but the effects of SNAP were unchanged. CONCLUSIONS: Endogenous NO released from microvascular endothelium may play an important physiologic role in the modulation of cellular respiration in skeletal muscle, and the loss of this regulatory function may contribute to peripheral metabolic disorders and poor exercise tolerance during heart failure.

2,4-Dinitrophenol↗
PubMed1996

Role of nitric oxide and its interaction with superoxide in the suppression of cardiac muscle mitochondrial respiration. Involvement in response to hypoxia/reoxygenation.

BACKGROUND: Nitric oxide (NO); superoxide anion (O2.d-); the reaction product of NO with O2.d-, peroxynitrite (ONOO-); and ischemia/reperfusion have all been reported to inhibit respiration in isolated mitochondria. However, the specific species involved in the inhibition of respiration in intact tissues are poorly understood. METHODS AND RESULTS: O2 consumption in isolated cardiac muscle from bovine calf hearts was quantified by use of a Clark-type electrode. Exogenous and endogenous sources of NO, from S-nitroso-N-acetylpenicillamine (SNAP) and bradykinin or carbachol, reversibly inhibited respiration, whereas the O2.- releasing agent, pyrogallol (PG), inhibited respiration in a manner that was only partially reversed when examined 15 minutes after the removal of PG. The generation of ONOO- with SNAP + PG caused a potentiation of the O2(-)-elicited inhibition of respiration when examined 15 minutes after the removal of the ONOO- generating system. Tiron (a scavenger of O2.-) did not alter the actions of SNAP, but it attenuated the direct inhibitory effects of PG +/- SNAP and essentially eliminated the suppression of respiration observed 15 minutes after removal of the O2.- or ONOO- generating system. Urate (a scavenger of ONOO-) antagonized only the actions of PG + SNAP. After exposure of muscle slices to a model of hypoxia (15 minutes) and reoxygenation (10 minutes), respiratory inhibition was observed. This reoxygenation-induced inhibition was potentiated by L-arginine, the substrate for NO biosynthesis, and was markedly blocked by nitro-L-arginine (an NO synthase inhibitor), Tiron, or urate. CONCLUSIONS: The potentially physiological reversible regulation of respiration in cardiac muscle by NO is converted to an effect that does not show rapid reversibility under conditions in which ONOO- forms, and this could contribute to cardiac dysfunction in situations such as hypoxia/reoxygenation.

Animals↗
PubMed1996

Modulation by atrial natriuretic factor of receptor-mediated cyclic AMP-dependent responses in canine pulmonary artery during heart failure.

1. Pacing-induced congestive heart failure (CHF) in dogs is associated with increased plasma levels of atrial natriuretic factor (ANF) and inhibition of receptor-mediated cyclic AMP-dependent relaxation in isolated pulmonary arteries (PA). Since ANF is known to be negatively coupled to adenylate cyclase, we studied cyclic AMP-mediated relaxation to isoprenaline (Iso) and arachidonic acid (AA) in PA from control dogs (C), dogs with pacing-induced CHF (CHF) and dogs with bilateral atrial appendectomy and CHF (ATR APP+CHF). 2. In CHF, plasma ANF levels increased from a baseline of 80 +/- 8 pg ml-1 to 283 +/- 64 pg ml-1 (P < 0.05), but the ATR APP+CHF group failed to show this increase (67 +/- 7 pg ml-1 vs 94 +/- 15 pg ml-1, P = NS). Plasma ANF levels, however, did not influence myocardial dysfunction in CHF. 3. The relaxation of 49 +/- 5% to 1 microM Iso in C was reduced to 23 +/- 4% in CHF (P < 0.05), but relaxation of 49 +/- 12% was observed in the ATR APP+CHF group (P = NS vs C). Relaxation responses to 10 microM AA were as follows: 77 +/- 5% (C, n = 8), 27 +/- 8% (CHF, n = 10, P < 0.05 vs C), and 93 +/- 5% (ATR APP+CHF, n = 5). The presence of CHF, or the plasma ANF levels, did not affect responses to cyclic GMP-mediated relaxing agents in PA. 4. These data indicate that the myocardial performance in CHF is not influenced by plasma ANF levels. However, altered cyclic AMP-mediated relaxation in PA during CHF is, in part, modulated by circulating ANF levels.

Acetylcholine↗
PubMed1996

Nitrogen dioxide causes pulmonary arterial relaxation via thiol nitrosation and NO formation.

Micromolar concentrations of nitrogen dioxide (NO2), a key metabolite of nitric oxide (NO) and peroxynitrite (ONOO-), were observed to cause a prolonged relaxation of isolated endothelium-removed rings of bovine pulmonary arteries (BPA) precontracted with 30 mM potassium. Relaxation to NO2 was markedly inhibited by 1 microM hemoglobin (Hb), 10 microM methylene blue (MB), and 10 microM LY-83583. The response to NO2 was enhanced in the presence of 1 mM reduced glutathione (GSH) or cysteine. The addition of NO2 to Krebs bicarbonate buffer (under 95% N2-5% CO2) containing 1 mM GSH or BPA resulted in an increase in NO formation (measured in head space gas). Relaxation to NO2 and NO formation were markedly decreased after GSH depletion by pretreatment of BPA with diethyl maleate. A high-performance liquid chromatography analysis of the products formed immediately after the addition of NO2 to GSH detected a previously isolated (but not identified) potent relaxing agent formed by a reaction of GSH with ONOO-, and this material comigrated with a synthetic product thought to be S-nitro-GSH (GSNO2). Nanomolar concentrations of GSNO2 caused a potent dose-dependent relaxation that was inhibited by Hb, MB, and LY-83583. Therefore NO2 appears to cause a prolonged guanosine 3',5'-cyclic monophosphate-mediated relaxation in BPA via thiol nitration and a subsequent time-dependent release of NO. Thus NO2 (and ONOO-) may function in a tissue hormonelike regulatory role in inflammatory processes in which large amounts of these species are produced.

Animals↗
PubMed1996

Oxygen-elicited responses in calf coronary arteries: role of H2O2 production via NADH-derived superoxide.

Our previous studies in isolated endothelium-removed calf pulmonary arteries suggest that PO2-elicited responses are primarily mediated through modulation of guanosine 3',5'-cyclic monophosphate via changes in the generation of H2O2 originating from superoxide anion (O2-.) produced by NADH oxidase activity. In the present study we examined the importance of this mechanism in PO2-elicited responses of endothelium-removed calf coronary arteries. NADH oxidase activity was found to be the major source of O2-. in the homogenate of endothelium-removed calf coronary arteries detected by lucigenin-elicited chemiluminescence. Precontracted endothelium-removed calf coronary arteries show a relaxation to hypoxia, and reoxygenation causes a transient additional relaxation before the recovery of normoxic levels of force. Under these conditions the detection of O2-. was decreased by hypoxia and a transient overproduction was observed during reoxygenation. The relaxation to reoxygenation, but not to hypoxia, was significantly inhibited by a scavenger of O2-. that prevents the formation of H2O2 (nitro blue tetrazolium), an inhibitor of NAD(P)H oxidases and other O2(-.)-generating flavoproteins (diphenyliodonium), and inhibition of the stimulation of soluble guanylate cyclase (LY-83583). A scavenger of O2-. that promotes H2O2 formation (Tiron) did not inhibit the PO2-elicited responses examined. Hypoxia and diphenyliodonium (but not Tiron) decreased the metabolism of endogenous H2O2 by catalase (as measured by the H2O2-dependent co-oxidation of methanol to formaldehyde by catalase), and reoxygenation caused a stimulation of H2O2 metabolism by catalase. The presence of endothelium resulted in minor modifications of the PO2 responses, which were partially mediated via prostaglandins and nitric oxide on the basis of the effects of indomethacin and nitro-L-arginine, respectively. These results suggest that in calf coronary arteries the stimulation of guanylate cyclase via H2O2 originating from NADH-derived O2-(.) production contributes to the transient relaxation to posthypoxic reoxygenation, but not the response to hypoxia.

Animals↗