nitroarginine and linsidomine

Topics: Acetylcholine; Animals; Brain; Central Nervous System; Digestive System; Enzyme Inhibitors; Humans; Molsidomine; Myenteric Plexus; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

We investigated the role of NO (nitric oxide) in the isolated intestine of the sea water adapted eel, by testing the effect of various donors on I(sc) (short-circuit current), due to net Cl(-) absorption in the control conditions. We found that the endogenous NO-synthase substrate l-arginine as well as two different NO donors, SNP (sodium nitroprusside) and SIN-1 (3-morpholinosydnonimine), produced a slow and gradual decrease of I(sc). The effect of SNP was reduced by the pretreatment with ODQ (1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one), a specific inhibitor of the soluble guanylyl cyclase, suggesting the involvement of cGMP (cyclic GMP) in some physiological actions of NO. The effect of the NO donors on I(sc) was similar to that observed when the tissues were perfused with solution in which the HCO(3)(-) buffer was substituted with Hepes buffer. In addition the NO donors produced a negligible effect on I(sc) when the tissues were perfused with Hepes buffer or in the presence of bilateral SITS(4-Acetoamido-4'-iso-thiocyanatostilbene-2,2'disulphonic acid), an inhibitor of the HCO(3)(-) transport mechanisms, operating on both cell membranes of the eel enterocyte and responsible for HCO(3)(-) uptake by the cell. Based on these observations we suggest that NO regulates I(sc) and hence the transepithelial ion transport indirectly by modulating the endocellular concentration of HCO(3)(-) and/or H(+). In addition it is likely that NO modulates the permeability of the paracellular pathway since SNP produced also an increase of the tissue conductance and a decrease of the magnitude of the dilution potential.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Anguilla; Animals; Arginine; Bicarbonates; Chlorides; Cyclic GMP; Diffusion Chambers, Culture; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Intestinal Absorption; Intestinal Mucosa; Intestines; Membrane Potentials; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; omega-N-Methylarginine; Oxadiazoles; Permeability; Quinoxalines; Time Factors

The modulation by spinal nitric oxide (NO) of descending pathways travelling through the dorsal lateral funiculus (DLF) is a mechanism proposed for the antinociceptive effects of drugs that changes the NO metabolism. In this study we confirm that a surgical incision in the mid-plantar hind paw of rats reduces the threshold to mechanical stimulation with von Frey filaments. The incisional pain was further increased in rats with ipsilateral DLF lesion. Intrathecal L-NOARG (50-300 microg), or SIN-1 (0.1-5.0 microg) reduced, while SIN-1 (10 and 20 microg) intensified the incisional pain in rats with sham or effective lesion of the DLF. Stimulation of the dorsal raphe (DRN) or anterior pretectal (APtN) nuclei with stepwise increased electrical currents (7, 14, 21, 28 and 35 microA r.m.s.) produced a current-related reduction of the incisional pain. These nuclei activate pain inhibitory pathways that descend to the spinal cord mainly through the DLF. Intrathecal SIN-1 (5 microg) reduced, SIN-1 (20 microg) decreased and L-NOARG (150 microg) did not change the EC50 for the DRN or APtN stimulation-induced reduction of incisional pain. We conclude that the antinociceptive effects of L-NOARG or low doses of SIN-1 are independent on the activity of descending pain control pathways travelling via the DLF, but the antinociceptive effect of stimulating electrically the DRN or APtN can be summated to the effect of low dose of SIN-1 or overcome by the high dose of SIN-1.

Topics: Analgesia; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Efferent Pathways; Electric Stimulation; Enzyme Inhibitors; Hindlimb; Injections, Spinal; Male; Mesencephalon; Molsidomine; Nitric Oxide Donors; Nitroarginine; Pain; Pain Threshold; Raphe Nuclei; Rats; Rats, Wistar; Spinal Cord

Emerging evidence indicates that some secondary bile acids interact functionally with muscarinic cholinergic receptors. Using thoracic aortic rings prepared from rats and mice, we examined the mechanism of deoxycholyltaurine-induced vasorelaxation. Increasing concentrations of both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from rat thoracic aortae. These effects were reduced by endothelial denudation and by treatment with an inhibitor of nitric oxide formation and with a synthetic acetylcholine:bile acid hybrid that acts as a muscarinic receptor antagonist. Likewise, both acetylcholine (1 nM to 0.1 mM) and deoxycholyltaurine (0.1 microM to 0.1 mM) stimulated relaxation of phenylephrine-constricted rings prepared from mouse thoracic aortae. These effects were reduced by endothelial denudation, addition of an inhibitor of nitric oxide formation, and by muscarinic M(3) receptor knockout. We conclude that the systemic vasodilatory actions of deoxycholyltaurine are mediated in part by a nitric oxide-, muscarinic M(3) receptor-dependent mechanism. In advanced liver disease, interaction of serum bile acids with endothelial muscarinic receptors may explain nitric oxide overproduction in the systemic circulation and resulting peripheral arterial vasodilation.

Topics: Acetylcholine; Adenosine Triphosphate; Animals; Aorta, Thoracic; Bile Acids and Salts; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Female; Genotype; In Vitro Techniques; Lithocholic Acid; Male; Mice; Mice, Inbred Strains; Mice, Knockout; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Phenylephrine; Rats; Rats, Sprague-Dawley; Receptor, Muscarinic M3; Taurodeoxycholic Acid; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

The effects of endogenous and exogenous nitric oxide (NO) on electrical activity were investigated in circular smooth muscle preparations isolated from the guinea-pig stomach antrum. The actions of endogenous NO were evaluated from the effects of inhibition of NO synthesis by N(omega)-nitro-L-arginine (nitroarginine), while those of exogenous NO were assessed from the effects of SIN-1, an NO donor. Antral circular smooth muscle generated slow potentials periodically at a frequency of about 1 cycle per min (cpm), and unitary potentials were also generated in a random fashion in the interval between slow potentials. Application of nitroarginine (10(-5) M) increased the frequency of slow potentials, with no significant alteration of the resting membrane potential and amplitude of slow potentials. Frequency analysis of unitary potentials revealed that nitroarginine also increased the spectral density at 0.01-1 Hz frequency. The refractory period for the generation of slow potentials evoked by depolarizing pulses was about 10 s, but was decreased to 6 s by nitroarginine. In the presence of nitroarginine, SIN-1 (10(-9)-10(-7) M) reduced the amplitude and frequency of slow potentials: low concentrations (<10(-8) M) reduced only the frequency of slow potentials, while higher concentrations (10(-8)-10(-7) M) reduced both the amplitude and frequency of slow potentials, in a concentration-dependent manner, before abolishing the slow potentials. The power spectrum of the unitary potentials indicated that SIN-1 (>10(-8) M) reduced the spectral density at 0.01-1 Hz frequency. The refractory period for the generation of slow potentials was increased again to about 10 s by SIN-1. Thus, the excitatory effects of nitroarginine could be antagonized by SIN-1, suggesting that the inhibitory effects of endogenous NO are comparable to those of exogenous NO produced by SIN-1. The results also suggested that the effects of NO on smooth muscle are insignificant and NO selectively inhibits the activity of intramuscular interstitial cells of Cajal (ICC-IM).

Topics: Action Potentials; Animals; Electromyography; Enzyme Inhibitors; Guinea Pigs; In Vitro Techniques; Male; Molsidomine; Muscle, Smooth; Myocytes, Smooth Muscle; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Pyloric Antrum

Nitric oxide (NO) is involved in hippocampal phenomena of synaptic plasticity. The present microdialysis study investigated a possible role of NO and of endothelial NO synthase (eNOS) activity in the control of hippocampal acetylcholine (ACh) release. 3-Morpholinosydnonimine (SIN-1), an NO donor, stimulated ACh release by 50%-70% when infused into the hippocampus of wild type C57B16 mice. Infusion of L-nitroarginine (L-NA), a broad-spectrum inhibitor of NO synthases, decreased hippocampal ACh efflux by approximately 50%. Mice lacking eNOS (eNOS knockouts) had identical basal effluxes of hippocampal ACh as wild type mice, and the responses to SIN-1 and L-NA were unchanged in the absence of eNOS activity. We conclude that nitric oxide (NO) stimulates hippocampal ACh release in a tonic fashion, but independently of eNOS activity.

Topics: Acetylcholine; Animals; Enzyme Inhibitors; Hippocampus; Mice; Mice, Inbred C57BL; Mice, Knockout; Molsidomine; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine

1. In this study, the role of endogenous H(2)O(2) as an endothelium-dependent relaxant factor was characterised in aortas from C57BL/6J and LDL receptor-deficient mice (LDLR(-/-)). 2. Aortic rings from LDLR(-/-) mice showed impaired endothelium-dependent relaxation to acetylcholine (ACh; 0.001-100 micro M) and to the Ca(2+) ionophore A23187 (0.001-3 micro M) compared with aortic rings from control mice. Endothelium-independent relaxation produced by the NO donor, 3-morpholino-sydnonimine (SIN-1) was not different between strains. 3. Pretreatment of vessels with L-NNA (100 micro M) or L-NNA (100 micro M) plus L-NAME (300 micro M) plus haemoglobin (10 micro M) markedly decreased, but did not abolish the relaxation to ACh in control mice. In the aortas from LDLR(-/-) mice treated with L-NNA (100 micro M), ACh induced a contractile effect. Catalase (800 and 2400 U ml(-1)) shifted to the right the endothelium-dependent relaxation to ACh in aortas from control but not from LDLR(-/-) mice. Aminotriazole (50 mM), which inhibits catalase, abolished its effect on control mice. Treatment of vessels with L-NNA and catalase abolished vasorelaxation induced by ACh. Indomethacin (10 micro M) did not modify the concentration-response curve to ACh. Superoxide dismutase (300 U ml(-1)) did not change ACh-induced relaxation in both strains. 4. Exogenous H(2)O(2) produced a concentration-dependent relaxation in endothelium-denuded aortic rings, which was not different between strains. 5. It is concluded that H(2)O(2) greatly contributes to relaxation to ACh in aorta from control mice. Endothelial-dependent relaxation to ACh is impaired in LDLR(-/-) mice. Reduced biosynthesis or increased inactivation of H(2)O(2) is the possible mechanism responsible for endothelial dysfunction in aortas of atherosclerosis-susceptible LDLR(-/-) mice.

Topics: Acetylcholine; Amitrole; Animals; Aorta, Thoracic; Arteriosclerosis; Catalase; Endothelium; Endothelium-Dependent Relaxing Factors; Hydrogen Peroxide; Indomethacin; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Molsidomine; Muscle Relaxation; Muscle, Smooth, Vascular; NG-Nitroarginine Methyl Ester; Nitroarginine; Phenylephrine; Receptors, LDL; Superoxide Dismutase

The effect of lesions induced by bilateral intracerebroventricular (i.c.v.) injection of quinolinate (250 nmol of QUIN/ventricle), a selective N-methyl-D-aspartate (NMDA) receptor agonist, on [3H]glutamate ([3H]Glu) binding to the main types of both ionotropic and metabotropic glutamate receptors (iGluR and mGluR) was investigated in synaptic membrane preparations from the hippocampi of 50-day-old rats. The membranes from QUIN injured brains revealed significantly lowered binding in iGluR (by 31%) as well as in mGluR (by 22%) as compared to the controls. Using selected glutamate receptor agonists as displacers of [3H]Glu binding we found that both the NMDA-subtype of iGluR and group I of mGluR are involved in this decrease of binding. Suppression of nitric oxide (NO) production by N(G)-nitro-L-arginine (50 nmol of NARG/ventricle) or the increase of NO generation by 3-morpholinylsydnoneimine (5 nmol of SIN-1/ventricle) failed to alter [3H]Glu or [3H]CPP (3-((D)-2-carboxypiperazin-4-yl)-[1,2-(3)H]-propyl-1-phosphonic acid; NMDA-antagonist) binding declines caused by QUIN-lesions. Thus, our findings indicate that both the NMDA-subtype of iGluR and group I of mGluR are susceptible to the QUIN-induced neurodegeneration in the rat hippocampus. However, the inhibition of NO synthesis did not reveal any protective action in the QUIN-evoked, NMDA-receptor mediated decrease of [3H]Glu binding. Therefore, the additional mechanisms of QUIN action, different from direct NMDA receptor activation/NO production (e.g. lipid peroxidation induced by QUIN-Fe-complexes) cannot be excluded.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Binding, Competitive; Cell Membrane; Excitatory Amino Acid Agonists; Glutamic Acid; Hippocampus; Kainic Acid; Male; Molsidomine; N-Methylaspartate; Nerve Degeneration; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Quinolinic Acid; Quisqualic Acid; Rats; Rats, Wistar; Tritium

We have previously demonstrated that dopaminergic neurons in midbrain-striatum slice co-cultures are more resistant to NMDA cytotoxicity than the same neuronal population in single midbrain slice cultures. Here, we show that dopaminergic neurons in midbrain-striatum co-cultures also exhibit resistance to the cytotoxicity of nitric oxide donors, 2,2'-(hydroxynitrosohydrazono)bis-ethanamine (NOC-18) and 3-morpholinosydnonimine (SIN-1). The cytotoxicity of NMDA (30 microM) in single cultures was significantly attenuated by the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (100 microM), whereas the toxicity in co-cultures was not. The levels of tyrosine residue nitration of tyrosine hydroxylase, a hallmark of the occurence of peroxynitrite anion in dopaminergic neurons, were lower in co-cultures than those in single cultures. Single cultures and co-cultures did not show appreciable differences in the number or distribution of NOS-containing neurons as assessed by NADPH diaphorase histochemistry. On the other hand, midbrain slices cultured with striatal slices showed higher levels of superoxide dismutase (SOD) activity as well as increased protein levels of Cu,Zn-SOD, than midbrain slices cultured alone. These results suggested that the generation of NO is involved in NMDA cytotoxicity on dopaminergic neurons, and that increased activity of SOD in co-cultures renders dopaminergic neurons resistant to NMDA cytotoxicity by preventing the formation of peroxynitrite.

Topics: Animals; Animals, Newborn; Cell Survival; Coculture Techniques; Corpus Striatum; Dihydrolipoamide Dehydrogenase; Dopamine; Mesencephalon; Molsidomine; N-Methylaspartate; Neurons; Neurotoxins; Nitric Oxide Donors; Nitroarginine; Nitroso Compounds; Organ Culture Techniques; Rats; Rats, Wistar; Superoxide Dismutase; Tyrosine; Tyrosine 3-Monooxygenase

This study was performed using intracellular and multiunit extracellular recording techniques in order to characterize the role of nitric oxide in the afferent synaptic transmission of the vestibular system of the axolotl (Ambystoma tigrinum). Bath application of nitric oxide synthase inhibitors N(G)-nitro-L-arginine (0.01microM to 10microM) and N-nitro-L-arginine methyl ester hydrochloride (0.1microM to 1000microM) elicited a dose-dependent decrease in the basal discharge of the semicircular canal afferent fibers. N(G)-Nitro-L-arginine also diminished the response to mechanical stimuli. Moreover, N(G)-nitro-L-arginine (1microM) produced a hyperpolarization associated with a decrease in the spike discharge and diminished the frequency of the excitatory postsynaptic potentials on afferent fibers recorded intracellularly. Nitric oxide donors were also tested: (i) S-nitroso-N-acetyl-DL-penicillamine (0.1microM to 100microM) increased the basal discharge and the response to mechanical stimuli. At the maximum effective concentration (100microM) this drug affected neither the amplitude nor the frequency of the excitatory postsynaptic potentials. However, it slightly depolarized the afferent neurons and decreased their input resistance. (ii) 3-Morpholino-sydnonimine hydrochloride did not significantly affect the basal discharge or the mechanically evoked peak response of afferent neurons at any of the concentrations used (1microM to 1000microM). However, after 10min of perfusion in the bath, 1microM and 10microM 3-morpholino-sydnonimine hydrochloride significantly modified the baseline of the mechanically evoked response, producing an increase in the mean spike discharge of the afferent fibers. These results indicate that nitric oxide may have a facilitatory role on the basal discharge and on the response to mechanical stimuli of the vestibular afferent fibers. Thus, nitric oxide probably participates in the sensory coding and adaptative changes of vestibular input in normal and pathological conditions.

Topics: Action Potentials; Ambystoma; Animals; Enzyme Inhibitors; Excitatory Postsynaptic Potentials; Hair Cells, Vestibular; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Acid; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Penicillamine; S-Nitroso-N-Acetylpenicillamine; Synapses; Synaptic Transmission

Low intrathecal (i.t.) doses of the nitric oxide (NO)-donor 3-morpholinosydnonimine (SIN-1) (0.1-2.0 microg/10 microl) reduced, while higher doses had no effect (5 or 100 microg/10 microl) or increased (10 and 20 microg/10 microl) the mechanical allodynia induced by chronic ligature of the sciatic nerve in rats. SIN-1 (0.1-100 microg/10 microl; i.t.) produced only antinociceptive effect in the rat tail flick test. The inhibitor of guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (4 microg/10 microl; i.t.), abolished the antinociceptive effects of SIN-1 in both tests and reduced the effect of high doses of SIN-1 in neuropathic rats. Hemoglobin (100 microg/10 microl; i.t.), a NO scavenger, inhibited the effect of low dose of SIN-1 and reduced the effect of high dose of SIN-1 in neuropathic rats. 8-Bromo-cGMP (125-500 microg/10 microl; i.t.), reduced the mechanical allodynia in neuropathic rats. The NO-synthase inhibitors, NG-nitro-L-arginine (L-NOARG) and NG-monomethyl-L-arginine (L-NMMA) (75-300 microg/10 microl; i.t.) reduced the mechanical allodynia evoked by nerve injury and increased the tail-flick latency, respectively. These effects were reduced and inhibited, respectively, by previous i.t. ODQ. The effect of L-NOARG was enhanced in a non-significant manner by hemoglobin. These results indicate that SIN-1 and NO-synthase inhibitors reduce pain through a spinal mechanism that involves activation of guanylate cyclase. The effects of SIN-1 vary depending on the dose and pain model utilized, but its most sensitive effect seems to be antinociception. However, high doses of the NO-donor can intensify ongoing pain.

Topics: Animals; Chronic Disease; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Hemoglobins; Injections, Spinal; Ligation; Male; Molsidomine; Nerve Compression Syndromes; Neuralgia; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Nociceptors; omega-N-Methylarginine; Oxadiazoles; Pain Measurement; Quinoxalines; Rats; Rats, Wistar; Sciatic Nerve

In this study we investigated the effect of immunostimulation on intracellular ATP level in rat glial cells. Rat primary astrocytes or C6 glioma cells were treated for 48 h with IFN-gamma, LPS or IFN-gamma plus LPS. These treatments increased NO production from the cells and a synergistic increase in NO production was observed with IFN-gamma plus LPS. Intracellular ATP level was decreased to about half the control level at the highest concentration of IFN-gamma (100 U/ml) plus LPS (1 microg/ml) without affecting cell viability. The level of intracellular ATP was inversely correlated with the extent of NO production from the glial cells. The increase in NO production is at least 6 h ahead of the initiation of ATP depletion, and NOS inhibitor N(G)-nitro-L-arginine (NNA) or Nomega-nitro-L-arginine methyl ester (L-NAME) inhibited NO production and ATP depletion. Exogenous addition of peroxynitrite generator 3-morpholinosydnonimine (SIN-1) and to a lesser extent NO generator S-nitroso-N-acetylpenicillamine (SNAP) depleted intracellular ATP level in a dose-dependent manner. The results from the present study imply that immunostimulation of rat glial cells decreases the intracellular ATP level without affecting cell viability. Considering the role of astrocytes as an essential regulator of the extracellular environment in the brain, the immunostimulation-induced decrease in intracellular ATP level may participate in the pathogenesis of various neurological diseases.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Astrocytes; Central Nervous System; Dose-Response Relationship, Drug; Encephalitis; Enzyme Inhibitors; Inflammation Mediators; Interferon-gamma; Intracellular Fluid; L-Lactate Dehydrogenase; Lipopolysaccharides; Molsidomine; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Penicillamine; Rats; Rats, Sprague-Dawley; S-Nitroso-N-Acetylpenicillamine; Tumor Cells, Cultured

The effects of a range of nitric oxide (NO)-related compounds on histamine release from human basophils and rat peritoneal mast cells were studied. Basal and immunologic histamine releases from human basophils were not affected by N(omega)-nitro-L-arginine, N(omega)-nitro-L-arginine methyl ester, aminoguanidine or methylene blue (all inhibitors of NO production), sodium nitroprusside (an NO donor), L-arginine (a substrate for NO synthase) or D-arginine (the inactive enantiomer of L-arginine). In rat peritoneal mast cells, NO donors such as sodium nitroprusside, sodium nitrite and sodium nitrate, and lipopolysaccharide (an inducer of NO synthase) had little effect on basal histamine release, while 3-morpholino-sydnonimine (SIN-1, an NO donor), L-arginine and D-arginine increased this release by up to threefold. None of the inhibitors of NO production had any striking effect on histamine release induced by anti-rat immunoglobulin E (IgE), compound 48/80, sodium fluoride, phospholipase C, 1,2-dioctanoyl-sn-glycerol or ionophore A23187. However, haemoglobin was found to inhibit histamine release by anti-rat IgE or A23187 by ca. 40%. Alone of the NO donors, low concentrations of L-arginine produced a mild inhibition of histamine release induced by anti-IgE, compound 48/80 and A23187, but not other ligands, while sodium nitroprusside dose-dependently inhibited (by a maximum of ca. 30%) histamine release by anti-rat IgE, sodium fluoride or A23187. Stimulation with a variety of secretagogues or treatment with L-arginine, D-arginine, lipopolysaccharide, SIN-1 or sodium nitroprusside had no effect on NO production. Similarly, L-arginine, D-arginine or sodium nitroprusside did not change intracellular cGMP levels. On the basis of these results, it is suggested that NO does not play a significant role in the modulation of histamine release from human basophils or rat peritoneal mast cells. The effects of L-arginine, D-arginine and sodium nitroprusside may involve mechanisms unrelated to NO.

Topics: Animals; Antibodies; Arginine; Basophils; Calcimycin; Dose-Response Relationship, Drug; Guanidines; Hemoglobins; Histamine; Humans; Immunoglobulin E; Male; Mast Cells; Methylene Blue; Molsidomine; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Nitroprusside; p-Methoxy-N-methylphenethylamine; Peritoneal Cavity; Rats; Rats, Sprague-Dawley; Sodium Fluoride; Sodium Nitrite

The involvement of nitric oxide (NO) in cerebral blood flow (CBF) stimulation by acetazolamide was studied in anaesthetised, mechanically ventilated Wistar rats. CBF was monitored by laser Doppler scanning. Acetazolamide induced a long-lasting significant rCBF-increase. Application of NG-Nitro-L-arginine (L-NNA), an inhibitor of all NO synthetases (NOS), prevented CBF stimulation by acetazolamide. Continuous infusion of the exogenous NO donor SIN-1 (3-morpholinosydnonimine) suppressed L-NNA induced increases of mean arterial blood pressure without effect on rCBF in comparison to baseline. Additional acetazolamide injection then again caused a significant increase of rCBF in spite of NOS-inhibition. We thus conclude that NO is involved in acetazolamide-induced CBF stimulation. The mere continuous presence of NO is sufficient to re-establish the acetazolamide-response in spite of NOS-inhibition. These data suggest that NO acts rather as a modulator than as a mediator of the acetazolamide-induced CBF response.

Topics: Acetazolamide; Animals; Blood Pressure; Carbonic Anhydrase Inhibitors; Cerebral Cortex; Cerebrovascular Circulation; Laser-Doppler Flowmetry; Male; Molsidomine; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Vasodilator Agents

Reactive oxygen species have been shown to be involved in the mutagenicity, clastogenicity, and apoptosis of mammalian cells treated with arsenic or cadmium. As these endpoints require several hours of cellular processing, it is not clear that reactive oxygen species damage DNA directly or interfere with DNA replication and repair. Using single-cell alkaline electrophoresis, we have detected DNA strand breaks (DSBs) in bovine aortic endothelial cells by a 4-h treatment with sodium arsenite (As) and cadmium chloride (Cd) in sublethal concentrations. As-induced DSBs could be decreased by nitric oxide (NO) synthase inhibitors, superoxide scavengers, and peroxynitrite scavengers and could be increased by superoxide generators and NO generators. Treatment with As also increased nitrite production. These results suggest that As-increased NO may react with O2*- to produce peroxynitrite and cause DNA damage. The results showing that Cd increased cellular H2O2 levels and that Cd-induced DSBs could be modulated by various oxidant modulators suggest that Cd may induce DSBs via O2*-, H2O2, and *OH. Nevertheless, the DSBs in both As- and Cd-treated cells seem to come from the excision of oxidized bases such as formamidopyrimidine and 8-oxoguanine, as the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg) increased DSBs in cells treated with As, 3-morpholinosydnonimine (a peroxynitrite-generating agent), Cd, or H2O2.

Topics: Amitrole; Animals; Antioxidants; Aorta; Arsenites; Bacterial Proteins; Cadmium Chloride; Catalase; Cattle; Cells, Cultured; Chromans; Citrulline; Ditiocarb; DNA Damage; DNA-Formamidopyrimidine Glycosylase; Endothelium, Vascular; Enzyme Inhibitors; Escherichia coli Proteins; Free Radical Scavengers; Hydrogen Peroxide; Molsidomine; Mutagens; N-Glycosyl Hydrolases; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Onium Compounds; Phenanthrolines; Reactive Oxygen Species; Sodium Compounds; Sodium Selenite; Superoxide Dismutase; Superoxides; Thiomalates; Thiourea; Uric Acid

The interaction between nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) was investigated in isolated circular smooth muscle cells and strips of the guinea-pig gastric fundus. VIP induced a concentration-dependent inhibition of carbachol-induced contraction in smooth muscle cells with a maximum at 10(-6) M. The relaxation by 10(-6) M VIP was inhibited for 79.1+/-5.8% (mean+/-s.e. mean) by the NO-synthase (NOS) inhibitor L-N(G)-nitroarginine (L-NOARG; 10(-4) M) in a L-arginine reversible way. Also the inducible NOS (iNOS) selective inhibitor N-(3-(acetaminomethyl)-benzyl)acetamide (1400 W; 10(-6) M) inhibited the VIP-induced relaxation, but its inhibitory effect was not reversed by L-arginine. When cells were incubated with the guanylyl cyclase inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ, 10(-6) M), the protein kinase A-inhibitor (R)-p-cyclic adenosine-3', 5'-monophosphothioate ((R)-p-cAMPS, 10(-6) M) and the glucocorticoid dexamethasone (10(-5) M), the relaxant effect of VIP was decreased by respectively 80.9+/-7.6, 77.0+/-11.6 and 87.1+/-4.5%. In circular smooth muscle strips of the guinea-pig gastric fundus, the VIP (10(-9) - 10(-7) M)-induced relaxations were not significantly influenced by 10(-4) M L-NOARG, 10(-6) M 1400 W, 10(-6) M ODQ and 10(-5) M dexamethasone. These results suggest that iNOS, possibly induced by the procedure to prepare the smooth muscle cells, is involved in the relaxant effect of VIP in isolated smooth muscle cells but not in smooth muscle strips of the guinea-pig gastric fundus. This study illustrates the importance of the experimental method when studying the influence of NOS inhibitors on the relaxation induced by VIP in gastrointestinal smooth muscle preparations.

Topics: Adenine; Adrenergic beta-Agonists; Animals; Atrial Natriuretic Factor; Carbachol; Colforsin; Cyclic AMP; Dexamethasone; Electric Stimulation; Enzyme Inhibitors; Gastric Fundus; Guinea Pigs; In Vitro Techniques; Isoproterenol; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Nitroprusside; Pinacidil; Tetrodotoxin; Thionucleotides; Vasoactive Intestinal Peptide

1. Guanosine 3', 5'-cyclic monophosphate (cyclic GMP)-dependent kinase I (cGKI) is a major receptor for cyclic GMP in a variety of cells. Mice lacking cGKI exhibit multiple phenotypes, including severe defects in smooth muscle function. We have investigated the NO/cGMP- and vasoactive intestinal polypeptide (VIP)/adenosine 3', 5'-cyclic monophosphate (cyclic AMP)-signalling pathways in the gastric fundus of wild type and cGKI-deficient mice. 2. Using immunohistochemistry, similar staining patterns for NO-synthase, cyclic GMP- and VIP-immunoreactivities were found in wild type and cGKI-deficient mice. 3. In isolated, endothelin-1 (3 nM - 3 microM)-contracted, muscle strips from wild type mice, electrical field stimulation (1 - 16 Hz) caused a biphasic relaxation, one initial rapid, followed by a more slowly developing phase. In preparations from cGKI-deficient mice only the slowly developing relaxation was observed. 4. The responses to the NO donor, SIN-1 (10 nM - 100 microM), and to 8-Br-cyclic GMP (10 nM - 100 microM) were markedly impaired in strips from cGKI-deficient mice, whereas the responses to VIP (0.1 nM - 1 microM) and forskolin (0.1 nM - 1 microM) were similar to those in wild type mice. 5. These results suggest that cGKI plays a central role in the NO/cGMP signalling cascade producing relaxation of mouse gastric fundus smooth muscle. Relaxant agents acting via the cyclic AMP-pathway can exert their effects independently of cGKI.

Topics: Animals; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Electric Stimulation; Female; Fluorescent Antibody Technique; Immunohistochemistry; Male; Mice; Mice, Knockout; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Receptor Cross-Talk; Signal Transduction; Stomach; Vasoactive Intestinal Peptide

This study asks which occurs first in time for remote responses: a dilation or a remote change in flow. Arteriolar diameter (approximately 20 microm) and fluorescently labeled red blood cell (RBC) velocity were measured in the cremaster muscle of anesthetized (pentobarbital sodium, 70 mg/kg) hamsters (n = 51). Arterioles were locally stimulated for 60 s with micropipette-applied 10 microg/ml LM-609 (alpha(v)beta(3)-integrin agonist), 10(-3) M adenosine, or 10(-3) M 3-morpholinosydnonimine (SIN-1, nitric oxide donor) as remote response agonists or with 10(-3) M papaverine, which dilates only locally. Observations were made at a remote site 1,200 microm upstream. With LM-609 or adenosine, the RBC velocity increased first (within 5 s), and the remote dilation followed 5-7 s later. N-nitro-L-arginine (100 microM) blocked the LM-609 (100%) and adenosine (60%) remote dilations. SIN-1 induced a concurrent remote dilation and decrease in RBC velocity (approximately 10 s), suggesting the primary signal was to dilate. Papaverine had no remote effects. This study suggests that, although remote responses to some agonists are induced by primary signals to dilate, additionally, network changes in flow can stimulate extensive remote changes in diameter.

Topics: Adenosine; Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Arterioles; Blood Flow Velocity; Cricetinae; Dose-Response Relationship, Drug; Enzyme Inhibitors; Erythrocytes; Male; Mesocricetus; Molsidomine; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Papaverine; Receptors, Vitronectin; Tetrodotoxin; Vasodilation; Vasodilator Agents

The functional role of nitric oxide (NO) and the guanylate cyclase/cGMP second messenger system was investigated in the mouse bladder. Electrical field stimulation and the NO-donor 3-morpholino-sydnonimin hydrochloride (SIN-1) did not induce relaxation of the carbachol-precontracted bladder. However, sodium nitroprusside (10(-3) M) was found to enhance the contractile response to electrical field stimulation by 24+/-6% (n=8; P<0.05) without affecting the contractile response to carbachol. The enhancement of bladder contractility evoked by sodium nitroprusside was inhibited by the guanylate cyclase inhibitor 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalime-1-one (ODQ; 10(-6) M). Incubation of bladder strips with SIN-1 and sodium nitroprusside caused an increase in cGMP accumulation as measured by radioimmunoassay. Immunohistochemical studies showed cGMP-immunoreactivity in nerve fibres and in stromal cells, but not in smooth muscle bundles after exposure to NO-donors. The results show that NO-donors have no inhibitory effect on smooth muscle tone in the mouse bladder, but that NO may have a functional role as an excitatory neuromodulator. The targets of endogenous NO in the bladder may be the demonstrated cGMP-positive structures, i.e., nerves and stromal cells.

Topics: Animals; Arginine; Carbachol; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Electric Stimulation; Enzyme Inhibitors; Female; In Vitro Techniques; Mice; Mice, Inbred BALB C; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Phosphodiesterase Inhibitors; Piperazines; Piperidines; Purines; Quinazolines; Sildenafil Citrate; Sulfones; Urethra; Urinary Bladder

We examined the importance of nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF), and neurogenic activity in agonist-induced vasodilation and baseline blood flow [i.e., nerve microvascular conductance (NMVC)] in rat sciatic nerve using laser Doppler flowmetry. Agonists were acetylcholine (ACh) and 3-morpholinosydnonimine (SIN-1). Vasodilation occurring despite NO synthase (NOS) and cyclooxygenase inhibition and showing dependence on K(+) channel activity was taken as being mediated by EDHF. NOS and cyclooxygenase inhibition with N(omega)-nitro-L-arginine (L-NNA) + indomethacin (Indo) revealed two phases of ACh-induced vasodilation: an initial, transient L-NNA + Indo-resistant vasodilation, peaking at 23 +/- 6 s and lasting 145 +/- 69 s, followed by sustained L-NNA + Indo-sensitive vasodilation. L-NNA alone did not affect sustained ACh-induced vasodilation but decreased baseline NMVC by 55%. In the presence of L-NNA + Indo, the K(+) channel blocker tetraethylammonium (TEA) inhibited transient ACh-induced vasodilation by 58% and reduced baseline NMVC by 25%. SIN-1-induced vasodilation increased fourfold in the presence of L-NNA, whereas the specific guanylyl cyclase inhibitor 1H-(1, 2, 4)oxadiazolo(4,3-alpha)quinoxalin-1-one abolished it. However, in homogenates of rat sciatic nerve, SIN-1-stimulated soluble guanylyl cyclase (sGC) activity was unaffected by L-NNA. TTX affected neither SIN-1- nor ACh-induced vasodilation. In conclusion, ACh-induced vasodilation consisted of two components, the first partially mediated by EDHF and the second by a vasodilatory prostanoid + NO. Baseline NMVC was dependent on NO and EDHF. Although L-NNA enhanced SIN-1-induced vasodilation, it had no effect on sGC-activity.

Topics: Acetylcholine; Analysis of Variance; Animals; Biological Factors; Blood Flow Velocity; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Guanylate Cyclase; Laser-Doppler Flowmetry; Male; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Potassium Channel Blockers; Potassium Channels; Rats; Rats, Wistar; Sciatic Nerve; Tetrodotoxin; Vasodilation; Vasodilator Agents

The effects of K(+) channel opener, nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate], on isolated human umbilical arteries were investigated at two temperatures: 37 degrees C and 25 degrees C. The purpose of this investigation was: (1) to confirm the relaxant effect of nicorandil, (2) to elucidate the influence of endothelium and temperature on nicorandil-induced relaxation, (3) to determine which of guanylate cyclase or ATP-sensitive K(+) channels was implicated in temperature-induced relaxation of smooth muscles. Rings, 3-mm-wide, were suspended in organ chambers for isometric force measurement. All solutions were aerated with 95% O(2)-5% CO(2) and maintained at 37 degrees C or 25 degrees C (cooling), pH 7.4. The presence of an intact endothelium was confirmed by immunohistochemistry. During the first set of experiments after contraction with 5-hydroxytryptamine (5-HT 10(-5) M), nicorandil (10(-9)-10(-4) M) was added to the organ chambers with controls and in with rings incubated with L-arginine, N-nitro-L-arginine (L-NNA) an inhibitor of nitric oxide (NO) synthase, [1-H-(1,2,4) oxadiazole (4,3-a) quinoxalin-1-one] (ODQ), a specific inhibitor of guanylate cyclase, or glibenclamide, an antagonist of nicorandil, all at 10(-5) M. In another set of experiments, rings were contracted with 5-HT (10(-5) M) and relaxed with 3-morpholinosydnonimine [SIN-1 (10(-9)-3x10(-5) M) or cromakalim (10(-9)-3x10(-5) M)]. Our results showed that nicorandil induced concentration-dependent relaxation. At 37 degrees C, in the control, the maximum relaxation was 90+/-5%, and 60+/-8% at 25 degrees C (P<0.01). However, the relaxation at 37 degrees C or 25 degrees C remained unchanged after pretreatment with L-arginine, L-NNA, this suggests that the same concentration of drugs used in this type of vessel does not appear to modulate the relaxant effect of nicorandil. On the other hand, we observed that the relaxant effect of SIN-1 was 72+/-5% at 37 degrees C and only 28+/-7% at 25 degrees C (P<0.01). However, relaxations with cromakalim were partly influenced by cooling. In the presence of ODQ, the nicorandil-induced relaxation observed at 37 degrees C or 25 degrees C was less than that in the control and in the rings incubated with glibenclamide. These results for human umbilical arteries indicate that cooling decreases the relaxation response of smooth muscles and that this is partly due to a decreased response to guanylate cyclase.

Topics: Adenosine Triphosphate; Arginine; Cromakalim; Dose-Response Relationship, Drug; Female; Glyburide; Guanylate Cyclase; Humans; In Vitro Techniques; Molsidomine; Muscle, Smooth, Vascular; Nicorandil; Nitroarginine; Oxadiazoles; Potassium Channels; Pregnancy; Quinoxalines; Serotonin; Temperature; Umbilical Arteries; Vasodilation; Vasodilator Agents

1. Isometric tension was recorded in isolated rings of aorta, carotid, coronary and mesenteric arteries taken from endothelial nitric oxide synthase knockout mice (eNOS(-/-) mice) and the corresponding wild-type strain (eNOS(+/+) mice). The membrane potential of smooth muscle cells was measured in coronary arteries with intracellular microelectrodes. 2. In the isolated aorta, carotid and coronary arteries from the eNOS(+/+) mice, acetylcholine induced an endothelium-dependent relaxation which was inhibited by N(omega)-L-nitro-arginine. In contrast, in the mesenteric arteries, the inhibition of the cholinergic relaxation required the combination of N(omega)-L-nitro-arginine and indomethacin. 3. The isolated aorta, carotid and coronary arteries from the eNOS(-/-) mice did not relax in response to acetylcholine. However, acetylcholine produced an indomethacin-sensitive relaxation in the mesenteric artery from eNOS(-/-) mice. 4. The resting membrane potential of smooth muscle cells from isolated coronary arteries was significantly less negative in the eNOS(-/-) mice (-64.8 +/- 1.8 mV, n = 20 and -58.4 +/- 1.9 mV, n = 17, for eNOS(+/+) and eNOS(-/-) mice, respectively). In both strains, acetylcholine, bradykinin and substance P did not induce endothelium-dependent hyperpolarizations whereas cromakalim consistently produced hyperpolarizations (- 7.9 +/- 1.1 mV, n = 8 and -13.8 +/- 2.6 mV, n = 4, for eNOS(+/+) and eNOS(-/-) mice, respectively). 5. These findings demonstrate that in the blood vessels studied: (1) in the eNOS(+/+) mice, the endothelium-dependent relaxations to acetylcholine involve either NO or the combination of NO plus a product of cyclo-oxygenase but not EDHF; (2) in the eNOS(-/-) mice, NO-dependent responses and EDHF-like responses were not observed. In the mesenteric arteries acetylcholine releases a cyclo-oxygenase derivative.

Topics: Acetylcholine; Animals; Aorta; Blood Vessels; Carotid Arteries; Coronary Vessels; Cromakalim; Dose-Response Relationship, Drug; Electrophysiology; Endothelium, Vascular; Enzyme Inhibitors; Homozygote; In Vitro Techniques; Indomethacin; Membrane Potentials; Mesenteric Arteries; Mice; Mice, Inbred C57BL; Mice, Knockout; Molsidomine; Muscle Relaxation; Muscle, Smooth, Vascular; Mutation; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Specific Pathogen-Free Organisms; Vasodilator Agents

1. The relationship between nitric oxide (NO) concentration measured with an NO-specific microelectrode and endothelium-dependent relaxation was investigated in isolated rat superior mesenteric artery contracted with 1 microM noradrenaline. 2. Acetylcholine (10 microM) induced endothelium-dependent simultaneous increases in luminal NO concentration of 21 +/- 6 nM, and relaxations with pD2 values and maximum of 6.95 +/- 0.32 and 97.5 +/- 0.7 % (n = 7), respectively. An inhibitor of NO synthase, N G-nitro-L-arginine (L-NOARG, 100 microM) inhibited the relaxations and increases in NO concentration induced by acetylcholine. 3. Oxyhaemoglobin (10 microM) reversed the relaxations and increases in NO concentrations induced by acetylcholine, S-nitroso-N-acetylpenicillamine (SNAP) and S-morpholino-sydnonimine (SIN-1), but not the relaxations induced with forskolin. Oxyhaemoglobin also decreased the NO concentration below baseline level. 4. In the presence of L-NOARG (100 microM), a small relaxation to acetylcholine (10 microM) of noradrenaline-contracted segments was still seen; oxyhaemogobin inhibited this relaxation and decreased the NO concentration by 14 +/- 4 nM (n = 4). 5. The NO concentration-relaxation relationship for acetylcholine resembled that for SNAP and SIN-1 more than for authentic NO. Thus while 7-17 nM NO induced half-maximal relaxations in response to SNAP or SIN-1, 378 +/- 129 nM NO (n = 4) was needed for half-maximal relaxation to authentic NO. 6. The present study provides direct evidence that the relaxation of the rat superior mesenteric artery with the endothelium-dependent vasodilator acetylcholine is correlated to the endogeneous release of NO. The study also suggests that NO mediates the L-NOARG-resistant relaxations in this artery, and that there is a basal NO release.

Topics: Acetylcholine; Animals; Endothelium, Vascular; Enzyme Inhibitors; In Vitro Techniques; Male; Mesenteric Artery, Superior; Microelectrodes; Molsidomine; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Oxyhemoglobins; Penicillamine; Rats; Rats, Wistar; S-Nitroso-N-Acetylpenicillamine

The present study investigates whether immunostimulated glial expression of inducible nitric oxide synthase influences the glucose deprivation-induced death of rat cerebellar granule cells (CGC). CGC/glia cocultures were immunostimulated by interferon-gamma (200 U/ml) and lipopolysaccharides (1 microg/ml) and 2 days later were challenged by glucose deprivation. Neurotoxicity was assessed by measuring the release of lactate dehydrogenase. Neither a 2-h glucose deprivation nor a 2-day immunostimulation altered the viability of CGC. A 2-day immunostimulation, however, markedly potentiated the glucose deprivation-induced death of CGC. The increased death of glucose-deprived CGC after immunostimulation was mimicked by the nitric oxide (NO) releasing reagent 3-morpholinosydnonimine (SIN-1) and was partially prevented by the NO synthase (NOS) inhibitor N(G)-nitroarginine. The increased death of glucose-deprived CGC either after immunostimulation or by SIN-1 was not altered by various N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists. Because superoxide dismutase and catalase, which remove superoxide anion, decreased the augmented death of glucose-deprived immunostimulated CGC, the reaction of NO with superoxide to form peroxynitrite appears to be implicated in the potentiated neurotoxicity. Our data indicate that immunostimulated glial cells potentiate the death of glucose-deprived neurons in part through the expression of inducible NOS but not through NMDA receptor activation. Potentiation of glucose-deprived CGC death by immunostimulated glial cells may be clinically implicated in the tendency of recurrent ischemic insults to be more severe and fatal than an initial ischemic insult.

Topics: Animals; Animals, Newborn; Cell Death; Cells, Cultured; Cerebellum; Coculture Techniques; Excitatory Amino Acid Antagonists; Glial Fibrillary Acidic Protein; Glucose; Interferon-gamma; Kinetics; Lipopolysaccharides; Microtubule-Associated Proteins; Molsidomine; Neuroglia; Neurons; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Penicillamine; Rats; Rats, Sprague-Dawley; S-Nitroso-N-Acetylpenicillamine

L-Arginine (4.7-18.8 mM) and 3-(4-morpholinyl)-sydonone imine hydrochloride (SIN-1; 1.15 mM) induced an increase in tetanic fade caused by indirect stimulation (180-200 Hz) of muscle. However, Wedensky inhibition, different from control, was not observed when the preparations treated with d-tubocurarine were directly stimulated by the same frequency. D-Arginine (9.4 mM) was ineffective in changing R values caused by indirect stimulation (180-200 Hz) of muscle. N(omega)-Nitro-L-arginine (73 mM) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 microM) did not produce any effect on Wedensky inhibition but did antagonize the tetanic fade induced by L-arginine (9.4 mM). The SIN-1 effect was antagonized by previous administration of ODQ (108 microM), which alone did not produce any effects on R values. These results indicate that NO acting at the presynaptic level increases the Wedensky inhibition induced by high frequency of stimulation applied on motor nerves, and its effect may be produced through the cGMP-GC pathway.

Topics: Animals; Arginine; Diaphragm; Electric Stimulation; Enzyme Inhibitors; Female; In Vitro Techniques; Male; Molsidomine; Muscle Contraction; Muscle, Skeletal; Neuromuscular Junction; Nitroarginine; Oxadiazoles; Phrenic Nerve; Quinoxalines; Rats; Rats, Wistar; Synaptic Transmission

1. The aims of this study were to investigate the effects of potassium (K+) channel blockers and the nitric oxide (NO) synthase inhibitor, L-nitroarginine (L-NOARG), on the response produced by acute hypoxia in rat intrapulmonary artery rings in vitro. 2. In rat phenylephrine-precontracted pulmonary artery rings, hypoxia (pO2 = 7 mmHg) induced a response which consisted of a rapidly developing initial contraction (phase 1), a transient relaxation (phase 2) and a slowly developing sustained contraction (phase 3) over 30 min. The NOS inhibitor, L-NOARG (300 microM), attenuated phase 1 and 3, and amplified phase 2 of the response to hypoxia. The voltage-gated K+ channel blocker 4-aminopyridine (4-AP) (10 mM) also abolished phase 3 and magnified phase 2 of the response to hypoxia. 3. The hypoxic response was not modified by the calcium-activated K+ channel (KCa) blockers, tetraethylammonium (TEA) (20 mM) or charybdotoxin (50 or 200 nM), nor by the ATP-dependent K+ channel (KATP), blocker, glibenclamide (10 microM). 4. L-NOARG (300 microM) and 4-AP (10 mM) also abolished carbachol-induced endothelium-dependent NO-mediated relaxation. Relaxation produced by the NO releasing agent 3-morpholino sydnonimine (SIN-1) was reduced by 4-AP (10 mM) and TEA (20 mM). 5. The data suggest that NO production is reduced during severe hypoxia in rat intrapulmonary artery rings and that this underlies the sustained phase of the hypoxic contraction. The data also suggests that 4-AP-sensitive K+ channels play an important role in the release and or action of NO, and therefore, in the response to hypoxia.

Topics: Animals; Cell Hypoxia; Endothelium, Vascular; Enzyme Inhibitors; Hypoxia; In Vitro Techniques; Male; Molsidomine; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen; Potassium Channel Blockers; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Vasoconstriction; Vasodilation

The activation of the nitric oxide (NO) production system and its involvement in the control of the lung fungal burden and in immunosuppression mechanisms were studied during the course of Paracoccidioides brasiliensis-infected mice. Mice that had been infected with the fungus were treated daily with a specific inhibitor of NO synthesis, N omega-nitro-L-arginine, or with buffered saline (control); NO production was assessed on the basis of spontaneous NO2- production by bronchoalveolar and peritoneal macrophages (Mphi) and of serum NO3- levels. The infection coursed with an elevation of NO3- levels. The Mphi produced NO2- and released TNF-alpha only after stimulation with LPS. In addition, the immunoproliferative responses of spleen cells that had been stimulated with the fungus Ag or with Con A were depressed. An examination of the lungs of infected animals showed a progressive increase in the size of the lesions. Treatment of the animals, which resulted in an inhibition of NO2- production by Mphi and a reduction of serum NO3- levels, caused the spontaneous release of TNF-alpha from infected animals and prevented the failure of the lymphoproliferative capacity of spleen cells. Furthermore, the treatment resulted in less pulmonary damage despite the fact that the lung fungal burden increased. It was also demonstrated that the NO donors S-nitroso-acetyl penicillamine and 3-morpholino-sydnonimine-hydrochloride were able to inhibit the growth of P. brasiliensis in vitro. These results suggest that although NO is important for the killing of the fungi, the activation of NO production in P. brasiliensis infection contributes to the occurrence of the immunosuppression observed during the course of the infection.

Topics: Animals; Cell-Free System; Drug Administration Schedule; Immunity, Cellular; Injections, Intraperitoneal; Lung; Lung Diseases, Parasitic; Lymphocyte Activation; Macrophages, Alveolar; Macrophages, Peritoneal; Male; Mice; Mice, Inbred C57BL; Molsidomine; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Nitroarginine; Paracoccidioides; Paracoccidioidomycosis; Penicillamine; Spleen; Tumor Necrosis Factor-alpha

We determined whether addition of hemoglobin to the plasma would inhibit endothelial-dependent dilation in brain where tight endothelial junctions limit hemoglobin extravasation. Pial arteriolar diameter was measured by intravital microscopy through closed cranial windows in anesthetized cats either without transfusion (hematocrit = 32%) or after exchange transfusion with an albumin or sebacyl-cross-linked human hemoglobin solution (hematocrit = 18%). Dilation of small, medium, and large arterioles to acetylcholine and ADP was not significantly altered by hemoglobin transfusion. The dilatory responses were inhibited by the nitric oxide synthase inhibitor NG-nitro-L-arginine, although significant dilation to 30 microM acetylcholine persisted in small arterioles in the control and albumin-transfused group but not in the hemoglobin-transfused group. The dilatory response to the nitric oxide donor 3-morpholinosydnonimine was unaffected by albumin or hemoglobin transfusion, but the response to nitroprusside was reduced by one-third after hemoglobin transfusion. When cross-linked hemoglobin was superfused through the cranial window, the acetylcholine response became inhibited at a hemoglobin concentration of 0.1 microM and was completely blocked at 10 microM. Because this concentration is substantially less than the 500 microM hemoglobin concentration in plasma after transfusion when there was no inhibition of the acetylcholine response, hemoglobin permeation of the blood-brain barrier was considered negligible. We conclude that exchange of red cell-based hemoglobin with plasma-based hemoglobin does not produce a more effective sink for endothelial-derived nitric oxide evoked by agonist receptor-mediated activation. Furthermore, decreased hematocrit does not affect agonist-evoked endothelial-dependent dilation.

Topics: Acetylcholine; Animals; Arterioles; Aspirin; Cats; Cross-Linking Reagents; Decanoic Acids; Endothelium, Vascular; Hemoglobins; Humans; Male; Molsidomine; Nitric Oxide Donors; Nitroarginine; Perfusion; Pia Mater; Salicylates; Serum Albumin; Vasodilation

Microglia have been shown to be immunostimulated by inflammatory cytokines and produce a number of toxic mediators. Here we report that immunostimulated microglia can synergistically enhance the N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in rat cerebellar granule cells (CGC) in culture. Neurotoxicity was assessed by morphological examination and by measuring the release of lactate dehydrogenase and DNA fragmentation. Cultured microglia were immunostimulated by interferon-gamma (200 U/ml) and lipopolysaccharides (10 microg/ml) and one or two days later they were used for co-culture with CGC. Co-culture of CGC with immunostimulated microglia resulted in a remarkable enhancement of the NMDA receptor-mediated death of CGC. This enhanced neurotoxicity was mimicked by the nitric oxide releaser 3-morpholinosydnonimine (SIN-1) or S-nitroso-N-acetylpenicillamine (SNAP). Superoxide dismutase and catalase, which stabilise NO by removing superoxide anion, ameliorated the potentiation of the NMDA-mediated death of CGC in co-culture with immunostimulated microglia, implying that reactions of NO with superoxide to form peroxynitrite can be implicated in the potentiated neurotoxicity. Our data indicate that immunostimulated microglia, which may involve in various neuropathologies, potentiate the NMDA receptor-mediated excitotoxicity in part through the expression of inducible nitric oxide synthase.

Topics: Animals; Apoptosis; Catalase; Cerebellum; Coculture Techniques; DNA Fragmentation; In Situ Nick-End Labeling; Interferon-gamma; L-Lactate Dehydrogenase; Lipopolysaccharides; Mice; Microglia; Molsidomine; N-Methylaspartate; Neurons; Nitrates; Nitric Oxide; Nitroarginine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Superoxide Dismutase

To establish which type of nerves (parasympathetic, sympathetic or sensory) produce nitric oxide in the rat lower urinary tract, chemical denervation of primary afferents and sympathetic nerves was carried out by systemic treatment with capsaicin and 6-hydroxydopamine, respectively, followed by identification of neuronal nitric oxide synthase immunoreactivity. Functional in vitro studies were also performed to examine whether the synthesis and release of nitric oxide was affected following treatment with the respective neurotoxins. Nerve fibres immunoreactive for substance P and calcitonin gene-related peptide were found in control tissue, but could not be detected following capsaicin treatment. In comparison, nitric oxide synthase-immunoreactive fibres appeared to be unaffected by capsaicin treatment. Administration of 6-hydroxydopamine resulted in a complete disappearance of tyrosine hydroxylase-immunoreactive nerves, whereas nitric oxide synthase-containing nerve fibres did not appear to be affected by the treatment. In ultrastructural studies, nitric oxide synthase immunoreactivity, as studied by colloidal gold particles, was found in the axoplasm and not in association with intraneuronal structures or synaptic vesicles. Gold particles representing substance P immunoreactivity were seen as clusters associated with large granular vesicles. In consecutive sections of nerve fibres, substance P and nitric oxide synthase were not found in the same axon profile. In functional studies on urethral tissue, application of capsaicin (1 microM) produced a long-lasting relaxation. The nitric oxide synthase inhibitor NG-nitro-L-arginine (0.1 mM) had no effect on this response. Systemic treatment with capsaicin or 6-hydroxydopamine had no effect on nerve-evoked, nitric oxide-mediated relaxations. The data suggest that nitric oxide synthase-containing nerves in the rat lower urinary tract do not belong to nerve populations sensitive to either the sympathetic neurotoxin, 6-hydroxydopamine, or the sensory neurotoxin, capsaicin.

Topics: Acetylcholinesterase; Animals; Antibody Specificity; Arginine Vasopressin; Calcitonin Gene-Related Peptide; Capsaicin; Enzyme Inhibitors; Female; Gold Colloid; Microscopy, Electron; Molsidomine; Neurons, Afferent; Neuropeptide Y; Nitric Oxide Synthase; Nitroarginine; Oxidopamine; Rats; Rats, Sprague-Dawley; Substance P; Sympathectomy, Chemical; Sympathetic Fibers, Postganglionic; Sympatholytics; Tyrosine 3-Monooxygenase; Urethra; Urothelium; Vasoconstrictor Agents; Vasodilator Agents

The effects of L-arginine and its analogues NG-nitro-L-arginine, NG-methyl-L-arginine, L-homoarginine and D-arginine on cytosolic calcium concentration were investigated to characterise the mechanisms of arginine-induced stimulation and to determine if nitric oxide production played a role in this stimulation. NIT-1 cells, a transgenic beta-cell line, were used for this purpose since they release insulin in response to typical beta-cell stimuli. Our data demonstrate that the arginine-induced increase in cytosolic calcium concentration was completely dependent on the influx of extracellular Ca2+ via verapamil-sensitive voltage-activated Ca2+ channels and that arginine stimulation requires the presence of a nutrient in order to cause an increase in cytosolic calcium concentration. The nutrient likely acted by closing the K+ ATP channels, since its effect could be inhibited by activation of these channels with diazoxide. L-arginine, as well as nitro-arginine and methyl-arginine which are not substrates for the production of nitric oxide, caused similar increases in cytosolic calcium concentration. Non-metabolisable arginine analogues homoarginine and D-arginine also caused increases in the cytosolic calcium concentration although not to the same extent. Insulin secretion was enhanced to the same extent by all analogues of arginine. It can be concluded that the arginine-induced increase in cytosolic calcium concentration in NIT-1 cells is attributable to an electrogenic effect following the transport of arginine leading to depolarisation of the plasma membrane potential, although metabolism of the amino acid itself may also partially contribute to the response.

Topics: Animals; Arginine; Calcium; Cell Line; Cytosol; Diazoxide; Homoarginine; Insulin; Insulin Secretion; Insulinoma; Kinetics; Mice; Mice, Transgenic; Molsidomine; Nitric Oxide; Nitroarginine; omega-N-Methylarginine; Pancreatic Neoplasms; Potassium Channels; Potassium Chloride; Tumor Cells, Cultured; Verapamil

Electrical stimulation of cerebellar parallel fibers (PF) increases cerebellar blood flow (BFcrb), a response that is attenuated by glutamate receptor antagonists and NO synthase (NOS) inhibitors. We investigated whether administration of NO donors could counteract attenuation by NOS inhibitors of vasodilation produced by PF stimulation. In halothane-anesthetized rats the cerebellar cortex was exposed and superfused with Ringer solution. PF were stimulated with microelectrodes (100 microA, 30 Hz), and BFcrb was recorded by a laser-Doppler probe. During Ringer superfusion, PF stimulation increased BFcrb by 56 +/- 7% and hypercapnia by 72 +/- 5% (n = 5). Superfusion with the nonselective NOS inhibitor N-nitro-L-arginine (L-NNA, 1 mM) reduced resting BFcrb and attenuated the response to PF stimulation (-47 +/- 5%) and hypercapnia (-46 +/- 7%; PCO2 = 50-60 mmHg). After L-NNA, superfusion with the NO donors 3-morpholinosydnonimine (100 microM, n = 5) or S-nitroso-N-acetyl-penicillamine (5 microM, n = 5) reestablished resting BFcrb (P > 0.05 vs. before L-NNA) and reversed L-NNA-induced attenuation of the response to hypercapnia (P > 0.05 vs. before L-NNA) but not PF stimulation (P > 0.05 vs. after L-NNA). Similar results were obtained when NOS activity was inhibited with the inhibitor of neuronal NOS 7-nitroindazole (50 mg/kg i.p.). Like NO donors, the guanosine 3',5'-cyclic monophosphate analog 8-bromoguanosine 3',5'-cyclic monophosphate (n = 5), administered after L-NNA, restored resting BFcrb and counteracted inhibition of the response to hypercapnia but not PF stimulation. In contrast to NO donors and 8-bromoguanosine 3',5'-cyclic monophosphate, the NO-independent vasodilator papaverine (100 microM, n = 5) had no effect on attenuation of responses to PF stimulation or hypercapnia. Thus NO donors are unable to reverse the effect of NOS inhibition on vasodilation produced by PF stimulation. The data support the hypothesis that the vascular response to PF stimulation, at variance with hypercapnia, requires NOS activation and NO production. Thus NO plays an obligatory role in vasodilation produced by increased functional activity in cerebellar cortex.

Topics: Animals; Blood Pressure; Carbon Dioxide; Cerebellum; Cyclic GMP; Electric Stimulation; Enzyme Inhibitors; Glutamic Acid; Hyperemia; Indazoles; Male; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen; Papaverine; Partial Pressure; Penicillamine; Rats; Rats, Sprague-Dawley; Regional Blood Flow; S-Nitroso-N-Acetylpenicillamine; Vasodilation

Nitric oxide (NO) is a potent vasodilator. We investigated the mechanisms responsible for this effect in the liver.. Isolated perfused rat liver and cultures of endothelial sinusoidal cells and hepatocytes were used.. L-arginine (10(-3) M) and NO donor Sin-1 (10(-5) M) respectively increased the liver flow by 52% (p<0.01) and 93% (p<0.01) vs controls. The NO synthase inhibitor Nw-nitro-L-arginine (10(-3) M) and the guanylate cyclase inhibitor methylene blue (10(-5) M) respectively decreased the basal liver flow by 26% and 16% (p<0.05) and inhibited the vasodilating effects of L-arginine. L-arginine (10(-3) M) increased nitrite concentration in hepatocyte culture (77.25+/-7.40 micromol x l(-1) vs 14.70+/-3.55 micromol x l(-1) in controls; p<0.01) and in liver endothelial cell culture (0.36+/-0.09 micromol x l(-1) vs 0.12+/-0.05 micromol x l(-1) in controls; p<0.05). Nw-nitro-L-arginine inhibited the basal production and abolished the L-arginine-induced production of nitrites both in hepatocyte and in liver endothelial cell cultures. The concentration of nitrites in the hepatocyte supernatant rose from 14.70+/-3.55 micromol x l(-1) to 150.50+/-45.55 micromol x l(-1) in the presence of a combination of interleukin-1beta, TNF alpha and interferon gamma.. Under basal conditions, NO regulates the vascular tone of liver circulation. Both liver endothelial cells and hepatocytes can be implicated. NO production by hepatocytes may increase during inflammation.

Topics: Animals; Arginine; Cells, Cultured; Cytokines; Endothelium, Vascular; Guanylate Cyclase; Liver; Liver Circulation; Male; Methylene Blue; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Vasodilation

Nitric oxide has recently been shown to inhibit the proliferation of several types of cells, including osteoclasts. Both osteoclasts and osteoblasts have inducible nitric oxide synthase and produce nitric oxide. Although the direct effect of nitric oxide on osteoblasts in general and osteoblast proliferation in particular has not been delineated, the authors performed studies to clarify the role of nitric oxide on osteoblast proliferation and metabolism. Cultures of human osteoblasts were exposed to 0.1, 1.0, and 10 microM of the nitric oxide releasing agent 3-morpholino sydnonimine (SIN-1) for 7 days. Cells were evaluated for proliferation and production of alkaline phosphatase and osteocalcin. Osteoblasts exhibited decreased proliferation relative to control cultures at 1.0 and 10 microM concentrations of SIN-1 (p < 0.05). Concentrations of 1.0 and 10 microM of SIN-1 effected a decreased production of osteocalcin and alkaline phosphatase (p < 0.05). The results of these studies indicate that nitric oxide may play a critical role by which osteoblasts exhibit self-regulation of mineral metabolism.

Topics: Alkaline Phosphatase; Cell Division; Cells, Cultured; Child, Preschool; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Molsidomine; Nitric Oxide; Nitroarginine; Osteoblasts; Osteocalcin

We hypothesize that the interaction between protein kinase C (PKC) and nitric oxide (NO) plays a role in the modulation of cerebral vascular tone, and the disturbance of this interaction following subarachnoid hemorrhage (SAH) results in vasospasm. To prove this hypothesis with direct evidence, PKC activities of smooth muscle cells of canine basilar arteries in the control and in the SAH groups were measured by an enzyme immunoassay method. N omega-nitro-L arginine (L-NA), an inhibitor of NO production, enhanced PKC activity. This enhancement was inhibited neither by 8-bromo-guanosine 3',5'-cyclic monophosphate (8-bromo-cGMP) nor SIN-1, a NO releasing agent. PKC activity in the SAH was significantly higher than in the control; however, no further enhancement was produced with L-NA. In the SAH, PKC activity was not inhibited either by 8-bromo-cGMP or SIN-1. We conclude that NO maintains an appropriate vascular tone through inactivation of PKC, and that this effect is disturbed following SAH, resulting in PKC-dependent vascular contraction, such as vasospasm. On the other hand, once PKC has been activated, NO precursors do not inhibit PKC. These facts indicate NO inactivates PKC through the inhibition of phosphatidylinositol breakdown.

Topics: Animals; Basilar Artery; Cyclic GMP; Dogs; Enzyme Activation; Enzyme Inhibitors; Female; Immunoenzyme Techniques; Ischemic Attack, Transient; Male; Molsidomine; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Protein Kinase C; Reference Values; Subarachnoid Hemorrhage

A method for the rapid detection of intracellular nitric oxide (NO) generation in dissociated cerebellar granule cells using dichlorofluorescin (DCFH) and flow cytometry was developed. DCFH can be oxidized specifically by NO and this was assessed by 1) the use of SIN-1 (10 nM-100 microM), an NO donor, that induced a concentration-dependent increase in dichlorofluorescein (DCF) fluorescence and 2) the use of hemoglobin (10 microM), an NO-scavenger, that totally inhibited the increase of fluorescence induced by SIN-1 (10 microM). This assay was used to determine the ability to kainate to stimulate NO production in dissociated cerebellar granule cells. Kainate (1 microM-10 mM) induced an increase in DCF fluorescence that was partially reduced by NG-nitro-L-arginine (1 nM-10 microM), a nitric oxide synthase inhibitor (61.9% +/- 9.1), or hemoglobin (10 microM) (55.0% +/- 4.1). The method described allows evaluation of the oxidation of DCFH to produce DCF as a parameter for measuring intracellular NO generation. The extent of DCFH oxidation by NO and ROS can be determined by using NO scavengers or NO synthase inhibitors.

Topics: Animals; Enzyme Inhibitors; Flow Cytometry; Fluoresceins; Kainic Acid; Molsidomine; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley

Inhibition of nitric oxide (NO) synthesis attenuates the hypercapnic cerebrovasodilation or the increases in cerebral blood flow (CBF) produced by acetylcholine (ACh), either topically applied or endogenously released in neocortex by stimulation of the basal forebrain cholinergic system. We investigated whether exogenous administration of NO, using NO donors, can reverse the attenuation of these responses by NO synthase (NOS) inhibitors. In halothane-anesthetized, ventilated rats the frontoparietal cortex was exposed and superfused with Ringer. CBF was monitored at the super fusion site by laser-Doppler flowmetry. The basal forebrain was stimulated (100 microA; 50 Hz) with microelectrodes stereotaxically implanted. Superfusion with the NOS inhibitor NG-nitro-L-arginine (L-NNA; 1 mM) reduced resting CBF (-38 +/- 2%; mean +/- SE) and attenuated the vasodilation elicited by hypercapnia (Pco2, 50-60 mmHg; -79 +/- 3%), ACh (10 microM; -83 +/- 7%), or basal forebrain stimulation (-44 +/- 2%) (P < 0.05, analysis of variance and Tukey's test). After L-NNA, topical application of 3-morpholinosydnonimine (SIN-1) (n = 7), S-nitroso-N-acetylpenicillamine (SNAP) (n = 6), or 8-bromoguanosine 3',5'-monophosphate (8-BrcGMP, n = 4) reestablished resting CBF (P > 0.05 from Ringer) and reversed the attenuation of the response to hypercapnia (P > 0.05 from Ringer). However, SIN-1 or SNAP failed to reverse the attenuation of the response to basal forebrain stimulation or topical ACh (P > 0.05 from L-NNA). After L-NNA, the NO-independent vasodilator papaverine (n = 4) reestablished resting CBF (P > 0.05 from Ringer) but failed to restore the hypercapnic vasodilation (P > 0.05 from L-NNA). The attenuation of hypercapnic response by the neuronal NOS inhibitor 7-nitroindazole was counteracted only partially by SIN-1 (n = 4) or 8-BrcGMP (n = 4). The data support the hypothesis that the vasodilation elicited by hypercapnia requires resting levels of NO for its expression, whereas the response to endogenous or exogenous ACh depends on agonist-induced NOS activation. In hypercapnia NO may act as a permissive factor by facilitating the action of other vasodilators, whereas in the vascular response initiated by ACh NO is likely to be the major mediator of smooth muscle relaxation.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Acetylcholine; Animals; Cerebrovascular Circulation; Dose-Response Relationship, Drug; Electric Stimulation; Enzyme Inhibitors; Hypercapnia; Indazoles; Male; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Papaverine; Prosencephalon; Rats; Rats, Sprague-Dawley; Vasodilation

Cytokines are released in the central nervous system following brain injury and disease. Several of those conditions are thought to involve the accumulation of extracellular glutamate at excitotoxic concentrations, and may involve compromised glial glutamate uptake. Using primary cultures of postnatal rat hippocampus, we studied the effect of three cytokines on astrocytic high-affinity glutamate uptake. After 24 hours incubation with either tumor necrosis factors alpha (TNF-alpha), interferon gamma (IFN-gamma) or interleukin-1 beta (IL-1 beta), astrocytic glutamate uptake was markedly attenuated in a dose-dependent manner. Cytokine effects were reversed by inhibition of nitric oxide synthase (NOS) using N omega-nitro-L-arginine (LNA), NG-monomethyl-L-arginine acetate (L-NMMA) or N omega-nitro-L-arginine methyl ester (LNAME). Moreover, application of the NO donors 3-morpholinosydnonimine (SIN-1) and s-nitroso-n-acetylpenicillamine (SNAP) mimicked cytokine inhibition of glutamate uptake. These data suggest that cytokine release can inhibit astrocytic glutamate uptake through a pathway that involves the liberation of nitric oxide. Astrocytic glutamate uptake may thus be compromised under conditions that are known to cause cytokine release such as nervous system injury, inflammation and ischemia.

Topics: Animals; Animals, Newborn; Biological Transport; Cells, Cultured; Cytokines; Enzyme Inhibitors; Glutamic Acid; Hippocampus; Humans; Interferon-gamma; Interleukin-1; Kinetics; Molsidomine; Neuroglia; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Penicillamine; Rats; Rats, Sprague-Dawley; Recombinant Proteins; S-Nitroso-N-Acetylpenicillamine; Tumor Necrosis Factor-alpha

Nonadrenergic, noncholinergic (NANC) relaxations of airway smooth muscle are thought to be mediated by vasoactive intestinal peptide (VIP) and nitric oxide (NO). Previous studies of the parasympathetic innervation of guinea pig trachealis suggest that the ganglion neurons mediating NANC relaxations but not cholinergic contractions are associated with the esophagus. In this study, the location of the neurons mediating these responses and their neurochemical phenotype was further assessed. Guinea pig tracheas maintained in organotypic culture for 2 days with the adjacent esophagus intact displayed cholinergic contractions and NANC relaxations to electrical field stimulation (EFS) as well as VIP and NO synthase (NOS) nerve fiber densities that were similar to those of control tracheas. By contrast, in tracheas cultured without the esophagus, NANC relaxations to EFS were not observed, and VIP and NOS nerve fiber densities were reduced > 80%. EFS-induced cholinergic contractions were unaffected by esophagus removal. These results provide further evidence that NANC relaxations are mediated by VIP and NO coreleased from noncholinergic parasympathetic nerve endings derived from neurons intrinsic to the esophagus.

Topics: Analysis of Variance; Animals; Atropine; Electric Stimulation; Enzyme Inhibitors; Esophagus; Guinea Pigs; Male; Molsidomine; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Myenteric Plexus; Nerve Fibers; Neurons; Nitric Oxide Synthase; Nitroarginine; Organ Culture Techniques; Parasympathetic Nervous System; Trachea; Vagus Nerve; Vasoactive Intestinal Peptide

The effects of cyclopiazonic acid (CPA), a specific inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase, on contractile activity of circular smooth muscle strips isolated from the antrum, corpus and fundus regions of the cat and guinea-pig stomach were studied. Contractile activity was recorded under isometric conditions, in organ baths. CPA, concentration dependently (3 x 10(-7)-3 x 10(-5) M) increased the tone of the cat and guinea-pig gastric fundus and corpus as well as the amplitude of the phasic contractions of the cat corpus and antrum, affecting their frequency. CPA had a dual action on the phasic contractions of the guinea-pig antrum: an increase at low concentrations (up to 10(-6) M) and inhibition at high concentrations (10(-6)-3 x 10(-5) M). Tetrodotoxin (10(-6) M), atropine (10(-6) M) and N omega-nitro-L-arginine (10(-4) M) did not change significantly the effects of CPA. Nifedipine completely inhibited the CPA-induced phasic contractions and partly inhibited the CPA-induced tonic contractions. The nitric oxide-releasing agents, sodium nitroprusside (10(-3) M) and 3-morpholino-sydnonimine (10(-3) M), completely inhibited the CPA-induced tonic and phasic contractions. CPA induced tonic contractions in the cat and guinea-pig gastric fundus precontracted by acetylcholine (10(-5) M) and inhibited the acetylcholine (10(-6) M)-induced phasic contractions in the guinea-pig gastric antrum and corpus. The results suggest multiple roles for sarcoplasmic reticulum Ca2+ stores and sarcoplasmic reticulum Ca(2+)-ATPase in the shaping of spontaneous and evoked tonic and phasic contractions of the stomach, and highlight important species and tissue differences.

Topics: Acetylcholine; Animals; Calcium; Calcium-Transporting ATPases; Cats; Guinea Pigs; In Vitro Techniques; Indoles; Molsidomine; Muscle Contraction; Muscle, Smooth; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Stomach; Time Factors; Vasodilator Agents

The aim was to examine whether (1) blood flow and vascular resistance are altered in response to exogenous nitric oxide and (2) whether endogenous synthesis of nitric oxide participates in the haemodynamic regulation of the submandibular, parotid and pancreatic glands. Experiments were performed on anaesthetized, artificially ventilated cats. Mean arterial blood pressure, heart rate, blood gases, cardiac output and tissue blood flow were determined before and 15 min after intravenous administration of either the nitric oxide donor SIN-1 (3-morpholinosydnonimine, 1 mg/kg, n = 10) or the competitive nitric oxide synthase inhibitor NOLA (NG-nitro-L-arginine, 30 mg/kg, n = 9) blood flow was measured by a radioactive-labelled microsphere method. In the SIN-1 group, in spite of a serious decrease in mean arterial blood pressure (p < 0.001), the blood flow in the glands remained unchanged. The vascular resistance decreased after SIN-1 in the submandibular and pancreatic glands (p < 0.001 and p < 0.05, respectively), and was slightly reduced in the parotid. The NOLA increased mean arterial blood pressure (p < 0.01) and reduced the blood flow in the submandibular and pancreatic glands (p < 0.01 and p < 0.001, respectively), but the decrease in the parotid was not significant. Vascular resistance increased after NOLA in all three glands (p < 0.05, p < 0.001 and p < 0.05). These findings suggest that basal nitric oxide production in these exocrine glands is sufficient to modulate vascular resistance. Moreover, the release of endogenous NO from the nerves and/or endothelium is probably involved in the regulation of vascular tone. The nitric oxide-dependent component of blood-flow regulation, however, seems to be less pronounced in the parotid gland.

Topics: Animals; Blood Flow Velocity; Blood Pressure; Cats; Endothelium, Vascular; Enzyme Inhibitors; Exocrine Glands; Hemodynamics; Male; Molsidomine; Nerve Fibers; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Pancreas; Parotid Gland; Regional Blood Flow; Submandibular Gland; Vascular Resistance; Vasodilator Agents

Nitric oxide (NO) exerts microbicidal effects on a broad spectrum of pathogens, including viruses, but its antiretrovirus properties have not yet been described. The purpose of this study was to determine whether NO inhibits murine Friend leukemia virus (FV) replication in vitro and to what extent NO may play a role in defenses against FV infection in mice. Three NO-generating compounds were studied: 3-morpholino-sydononimine (SIN-1), sodium nitroprusside (SNP), and S-nitroso-N-acetylpenicillamine (SNAP). The effects of these three compounds were compared with those of their controls (SIN-1C, potassium ferricyanide, and N-acetylpenicillamine, respectively), which do not generate NO and with that of sodium nitrite (NaNO2). SIN-1, SNP, and SNAP inhibited FV replication in dunni cells in a concentration-dependent manner. In contrast, no significant inhibitory effect was observed with the three controls or NaNO2. Furthermore, the addition of superoxide dismutase did not alter the inhibitory effect of SIN-1, which is also known to generate superoxide anions. No dunni cell toxicity was observed in the range of concentrations tested. We also assessed the effect of NO produced by activated macrophages on FV replication. Macrophages activated by gamma interferon and lipopolysaccharide inhibited FV replication in a concentration-dependent manner. This inhibition was due in part to NO production, since it was reversed by NG-monomethyl L-arginine, a competitive inhibitor of NO synthase. In vivo administration of NG-nitro-L-arginine methyl ester, a competitive inhibitor of NO synthase, significantly increased the viral load in spleen cells of FV-infected mice. These results suggested that NO may play a role in defenses against the murine Friend leukemia retrovirus.

Topics: Animals; Antiviral Agents; Arginine; Cell Line; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fibroblasts; Friend murine leukemia virus; Kinetics; Lipopolysaccharides; Macrophages, Peritoneal; Male; Mice; Mice, Inbred DBA; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Penicillamine; S-Nitroso-N-Acetylpenicillamine; Sodium Nitrite; Virus Replication

Topics: Animals; Arginine; Aspirin; Blood Pressure; Cats; Epoprostenol; Extracorporeal Circulation; Fibrinolysis; Heparitin Sulfate; Iloprost; Infusions, Intravenous; Injections, Intravenous; Molsidomine; Nitric Oxide; Nitroarginine; Platelet Aggregation; Streptokinase; Thrombosis; Vasodilator Agents

1. The present study investigates whether or not chronic feeding of rats with a diet enriched in fish oil affects the reactivity of balloon-injured carotid arteries. The left carotid arteries were injured in vivo by the repeated passage of a balloon catheter. Both the right (control artery) and the left carotid arteries were excised 24 h after the injury, and suspended in organ chambers for the measurement of changes in isometric tension in the presence of indomethacin. 2. Phenylephrine evoked similar concentration-contraction curves in the right (control) carotid arteries without endothelium from control and fish oil-fed rats. Balloon injury decreased the contractility of carotid arteries to phenylephrine in both types of rats and the pEC50 for phenylephrine was significantly decreased in balloon-injured arteries from control rats compared to those obtained in arteries from fish oil-fed rats (pEC50 7.59 +/- 0.1 and 7.28 +/- 0.06, respectively) while maximal contractions were similar (1.93 +/- 0.15 g and 1.79 +/- 0.12 g, respectively). 3. The treatment of control right carotid arteries without endothelium with either NG-nitro-L-arginine (an inhibitor of nitric oxide synthase) or superoxide dismutase (which protects nitric oxide from degradation) did not affect significantly the contractions to phenylephrine in either group. In these preparations, methylene blue (an inhibitor of soluble guanylate cyclase) decreased slightly but significantly maximal contractions to phenylephrine in both groups. The treatment of balloon-injured carotid arteries with NG-nitro-L-arginine or methylene blue partly restored contractions to phenylephrine in arteries from both types of rat. Superoxide dismutase further depressed the contractility to the alpha l-adrenoceptor agonist in balloon-injured arteries from control diet-fed rats but had no effect in balloon-injured preparations from fish oil-fed rats.4. 3-Morpholino-sydnonimine (SIN-1, a donor of nitric oxide) evoked similar concentration-dependent relaxations in control and balloon-injured carotid arteries from both types of rat.5. Balloon injury caused an increase in the tissue content of cyclic GMP in carotid arteries from control diet-fed rats. This production of cyclic GMP was abolished by N0-nitro-L-arginine. Superoxide dismutase potentiated significantly the production of cyclic GMP caused by balloon injury in control but not in fish oil-fed rats.6 These observations confirm that in vivo balloon injury causes the pro

Topics: Analysis of Variance; Animals; Arginine; Blood Pressure; Body Weight; Carotid Arteries; Carotid Artery Injuries; Catheterization; Cyclic GMP; Endothelium, Vascular; Fatty Acids; Fish Oils; Indomethacin; Isometric Contraction; Male; Methylene Blue; Molsidomine; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Phenylephrine; Rats; Rats, Wistar; Superoxide Dismutase; Vascular Resistance; Vasodilator Agents

The relaxation to bradykinin in canine coronary arteries is mediated by endothelium-derived nitric oxide (NO) and hyperpolarizing factor (EDHF). Desensitization to the kinin was induced by incubation of canine coronary arteries with endothelium with 10(-8) M bradykinin for 30 min. After washout, tissues were contracted with prostaglandin F2 alpha, and concentration-relaxation curves to bradykinin were obtained in control and desensitized arteries treated with indomethacin. After desensitization, there was a shift to the right of the concentration-relaxation curves to bradykinin. However, the elevation in guanosine 3',5'-cyclic monophosphate (cGMP) levels evoked by bradykinin was similar in both groups of tissues. The curves to bradykinin obtained in the presence of NG-nitro-L-arginine (an NO synthase inhibitor) were depressed, whereas those obtained in arteries contracted with potassium (to eliminate the EDHF-mediated relaxation) were not affected by the desensitization. Addition of NG-nitro-L-arginine, oxyhemoglobin, or methylene blue before the desensitization procedure preserved, whereas 3-morpholinosydnonimine (SIN-1, a donor of NO) and 8-bromoguanosine 3',5'-cyclic monophosphate impaired, the EDHF-mediated relaxation to bradykinin. Thus the selective impairment of the EDHF-dependent relaxation to bradykinin may be mediated by NO, acting mainly through increased production of cGMP.

Topics: Animals; Arginine; Arteries; Bradykinin; Coronary Vessels; Cyclic GMP; Dogs; Drug Resistance; In Vitro Techniques; Methylene Blue; Molsidomine; Nitroarginine; Oxyhemoglobins; Potassium; Vasodilation; Vasodilator Agents

1. Recent experiments suggest that acetylcholine (ACh) may exert myocardial protective effects during ischaemia (I) and reperfusion (R). The present study was designed (i) to assess whether ACh limits infarct size and protects coronary endothelial cells in a rat model of I and R, (ii) to evaluate the role of ATP-sensitive potassium (KATP) channels and nitric oxide (NO) in the beneficial effect of ACh (iii) to evaluate whether the protective effect of ACh also extends to coronary endothelial cells and (iv) to assess whether ACh contributes to the beneficial effect of preconditioning. 2. Anaesthetized rats were subjected to 20 min I (left coronary artery occlusion) and 2 h of R. Infarct size was assessed by triphenyltetrazolium (TTC) staining and expressed as a % of the area at risk (India ink injection). Vascular studies were performed on 1.5-2 mm coronary segments (internal diameter 250-300 micros) removed distal to the site of occlusion and mounted in wire myographs. 3. ACh limited infarct size (from 59 +/- 3 to 26 +/- 5%, P < 0.01), and this was prevented by atropine (46 +/- 7%; P < 0.05 vs ACh), but not by the inhibitor of KATP channels, glibenclamide (29 +/- 8%). The inhibitor of NO synthesis NG-nitro L-arginine did not affect infarct size (54 +/- 5%) but abolished the beneficial effect of ACh (59 +/- 8%; P < 0.05 vs ACh), whereas the NO donor 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1 limited infarct size to the same extent as ACh (28 +/- 6%). Preconditioning also limited infarct size (5 +/- 2%, P< 0.01 vs control), and this was not affected by atropine (6 +/- 2%). I and R induced a significant decrease in the endothelium-dependent relaxations of isolated coronary arteries toACh (maximal response: sham: 58+/-4; I/R: 25+/-5%; P<0.01) and this dysfunction was prevented by prior in vivo treatment with ACh (55+/-7%; P<0.01 vs I/R) or (SIN-1 50+/-5%; P<0.05 vs I/R).4 Thus, in the rat model, ACh is able to stimulate potent endogenous protective mechanisms during I and R, which are evident both at the level of myocardial and coronary endothelial cells, and appear entirely mediated through the production of NO. Pharmacological stimulation of this endogenous protective mechanism may constitute a new approach in the treatment of acute myocaridal ischaemia.

Topics: Acetylcholine; Animals; Arginine; Blood Pressure; Coronary Vessels; Disease Models, Animal; Endothelium, Vascular; Heart Rate; In Vitro Techniques; Male; Molsidomine; Myocardial Infarction; Myocardial Ischemia; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Potassium Channel Blockers; Rats; Rats, Wistar; Vasodilator Agents

Nitric oxide (NO) is a messenger molecule that is produced from L-arginine by NO synthase (NOS). Some NOS isoforms are present in cells constitutively, whereas others can be induced by cytokines. Recent evidence suggests that NO inhibits intracellular pH regulation by the vacuolar H(+)-adenosinetriphosphatase (ATPase) in macrophages, which contain an inducible form of NOS. The vacuolar H(+)-ATPase is involved in proton secretion in intercalated cells in the collecting duct. We have therefore examined the effect of NO on bafilomycin-sensitive H(+)-ATPase activity in individual cortical collecting ducts (CCD) microdissected from collagenase-treated kidneys of normal rats using a fluorometric microassay. Incubation of CCD with the NO donors, sodium nitroprusside (0.1 and 1 mM) or 3-morpholino-sydnonimine hydrochloride (SIN-1, 30 microM), caused a dose-dependent decrease in H(+)-ATPase activity. Incubation of CCD with lipopolysaccharide (LPS) and interferon-gamma, which induces NOS in macrophages, decreased H(+)-ATPase activity by 85%. This effect was prevented by simultaneous incubation with N omega-nitro-L-arginine, a competitive inhibitor of NOS, indicating that the decrease in H(+)-ATPase activity was caused by NO production. Incubation with 8-bromo-guanosine 3',5'-cyclic monophosphate (cGMP) also inhibited H(+)-ATPase activity, suggesting that NO may exert its effect in the CCD via activation of guanylyl cyclase and production of cGMP. Immunohistochemistry using antibodies to the macrophage-type NOS revealed strong labeling of intercalated cells in the CCD, confirming the presence of NOS in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Oxidoreductases; Animals; Anti-Bacterial Agents; Arginine; Cyclic GMP; Enzyme Induction; Ethylmaleimide; Female; In Vitro Techniques; Interferon-gamma; Kidney Tubules, Collecting; Kinetics; Lipopolysaccharides; Macrolides; Macrophages; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Proton-Translocating ATPases; Rats; Rats, Sprague-Dawley; Vacuoles

Nonadrenergic, noncholinergic (NANC) relaxations were elicited by field stimulation (1-16 Hz, 1 msec, 12 V for 15 sec) of guinea pig trachea desensitized with capsaicin (3 microM); pretreated with atropine (1 microM), propranolol (1 microM), indomethacin (3 microM) and alpha-chymotrypsin (2 U/ml) and contracted with 3 microM histamine. The nitric oxide (NO) synthase inhibitor L-nitro-N-arginine (L-NNA) significantly inhibited these responses, which is indicative of NO involvement. The ability of the large conductance Ca(++)-activated K+ channel antagonists iberiotoxin (IbTx) and charybdotoxin (ChTx) and the small conductance Ca(++)-activated K+ channel antagonist apamin to modify relaxations to NANC nerve stimulation and to the NO donor 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1) was studied. Both IbTx (100 nM) and ChTx (100 nM) were found to inhibit the L-NNA-sensitive relaxations elicited by field stimulation and to inhibit the relaxations to SIN-1. In contrast, apamin did not inhibit the relaxations to either field stimulation or SIN-1. These results suggest that in the guinea pig trachea, responses to endogenous or exogenously added NO are at least in part mediated by the large conductance Ca(++)-activated K+ channel.

Topics: Animals; Arginine; Charybdotoxin; Dose-Response Relationship, Drug; Electric Stimulation; Guinea Pigs; In Vitro Techniques; Male; Molsidomine; Muscle Relaxation; Nitric Oxide; Nitroarginine; Peptides; Potassium Channels; Scorpion Venoms; Trachea

Topics: Acetylcholine; Adenosine Triphosphate; Amino Acid Oxidoreductases; Analgesics; Animals; Arginine; Blood Pressure; Blood Transfusion; Brain; Cats; Cerebral Arteries; Cerebral Cortex; Cerebrovascular Circulation; Electroencephalography; Hemorrhage; Hypotension; Indazoles; Male; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Norepinephrine; Organ Specificity; Parietal Lobe; Pituitary Gland; Regional Blood Flow; Spinal Cord; Vasodilator Agents

The effects of intracerebral perfusion of the nitric oxide (NO) donor 3-morpholino-sydnonimine (SIN-1) and the nitric oxide synthase inhibitor N-nitroarginine (NARG) on the extracellular concentrations of glutamate (GLU) and gamma-aminobutyric acid (GABA) in striatum and CA1 area of the hippocampus were studied. Continuous push-pull perfusions at a flow rate of 20 microliters min-1 were performed in the conscious rat. SIN-1 (100, 200, and 400 microM) and NARG (100 microM) were perfused over 20 min. In both striatum and CA1 SIN-1 increased extracellular concentrations of GLU (maximal increase 150% and 197% of baseline, respectively) and GABA (maximal increase 202% and 204% of baseline, respectively). NARG had no effects on extracellular levels of GLU and GABA in either area. These results are consistent with the hypothesis that NO acts as a modulator of GLU and GABA release in both striatum and hippocampus. This study is the first to report the potentiation of GLU and GABA release by NO in CA1 area of the hippocampus in the conscious rat.

Topics: Amino Acid Oxidoreductases; Animals; Antihypertensive Agents; Arginine; Chromatography, High Pressure Liquid; gamma-Aminobutyric Acid; Glutamic Acid; Hippocampus; Male; Molsidomine; Neostriatum; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Spectrometry, Fluorescence

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Calcium; Cells, Cultured; Cerebellar Cortex; Cyclic GMP; Electron Spin Resonance Spectroscopy; Enzyme Activation; Epilepsy; Feedback; Free Radicals; Glutamic Acid; Guanylate Cyclase; Kindling, Neurologic; Mice; Molsidomine; N-Methylaspartate; Nerve Tissue Proteins; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Receptors, N-Methyl-D-Aspartate

Topics: Aconitate Hydratase; Adenocarcinoma; Amino Acid Oxidoreductases; Animals; Arginine; Cell Line; Interferon-gamma; Iron-Regulatory Proteins; Leukemia P388; Lipopolysaccharides; Macrophages; Mice; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Recombinant Proteins; RNA-Binding Proteins; RNA, Messenger; Tumor Cells, Cultured; Vasodilator Agents

The role of nitric oxide (NO) inhibition on liver circulation during sepsis is unknown. To answer this question, we studied the effects of L-arginine (the substrate for the NO synthase), linsidomine (a direct NO donor), and N omega-nitro-L-arginine (an NO inhibitor) on the liver circulation in anesthetized rabbits previously injected with endotoxin (Escherichia coli, Salmonella enteridis, and Salmonella minnesota, 400 micrograms each). After endotoxin administration, and without fluid resuscitation, rabbits showed a hypodynamic shock with decrease in mean arterial pressure (MAP) and aortic blood flow velocity. Portal vein blood flow velocity decreased, whereas hepatic artery blood flow velocity increased. Saline or treatments were injected, 75 min after endotoxin administration. In saline-treated rabbits, MAP, aortic and portal vein blood flow velocities remained steady but hepatic artery blood flow velocity decreased. Only N omega-nitro-L-arginine (7.5 mg/kg, intravenously) significantly increased MAP compared to saline treatment. However, aortic, portal vein, and hepatic artery blood flow velocities were lower in rabbits treated with N omega-nitro-L-arginine than in saline-treated rabbits. L-Arginine (600 mg/kg, intravenously) increased aortic blood flow and portal vein blood flow velocity with no change on hepatic artery blood flow velocity. In contrast, linsidomine (1 mg) increased both hepatic flows. These results show that NO inhibition after endotoxin injection reduces systemic and liver flows, while NO release from linsidomine improves them. These findings question the usefulness of NO inhibition during septic shock, particularly as hepatic failure frequently occurs in the evolution of the disease.

Topics: Animals; Arginine; Blood Flow Velocity; Blood Pressure; Hepatic Artery; Liver Circulation; Male; Mesenteric Arteries; Molsidomine; Nitric Oxide; Nitroarginine; Portal Vein; Rabbits; Shock, Septic; Vasodilator Agents

Effects of NO-donors (3-morpholinosydnonimine-SIN-1 and sodium nitroprusside NaNP) on the accumulation and degradation of oxidized LDL (ox-LDL) by macrophages were studied. Ox-LDL, but not native-LDL (n-LDL) suppressed the LPS-stimulated biosynthesis of NO by macrophages. SIN-1 at low concentrations < 100 microM was without any effect while SIN-1 at high concentration (300 microM) and NaNP (30-300 microM) stimulated the accumulation and degradation of ox-LDL by macrophages. The pretreatment of macrophages with NG-monomethyl-L-arginine (L-NMMA, 3 microM) for 24 hours had the same stimulatory effect. The inhibition of endogenous formation of NO, by L-NMMA profoundly changed the pattern of action of NO-donors on ox-LDL catabolism by macrophages; the stimulatory action of SIN-1 was transformed to the inhibitory action on the accumulation and degradation of ox-LDL whereas NaNP lost its stimulatory action entirely. Our interpretation of this unexpected interactions between SIN-1, NaNP and L-NMMA is as follows. Endogenous NO in macrophages inhibits the accumulation of ox-LDL and therefore, the stimulatory effect of L-NMMA has been overcome by exogenous NO from SIN-1. However, NO at high concentrations promotes lipid accumulation in macrophages and thereby, in the absence of L-NMMA, SIN-1 at high concentrations and NaNP produced a paradoxical stimulatory effect in macrophages. NaNP is not a proper NO-donor and its mode of action differed from that of SIN-1. In conclusion, NO at low physiological concentrations keeps scavenger receptors of macrophages downregulated and hence endogenous NO may show anti-atherogenic properties.

Topics: Animals; Arginine; Lipoproteins, LDL; Macrophages; Molsidomine; Nitric Oxide; Nitroarginine; Nitroprusside; Oxidation-Reduction; Rats; Rats, Wistar

This study was designed to determine if nitric oxide (NO) has direct effects on heart rate or if it is involved in the chronotropic actions of adrenergic or cholinergic stimulation. Right atria were isolated from hearts of adult male rats, bathed in Krebs-Henseleit buffer (37 degrees C), and used to monitor spontaneous rate. For comparison, ring segments of thoracic aorta were also suspended in the Krebs-Henseleit solution and used to examine vascular actions of various agents. The dose-dependent chronotropic effects of acetylcholine (10(-7)-10(-3) M) and norepinephrine (10(-8)-3 x 10(-4) M) in right atria were not affected by pretreatment with 10(-4) M N-nitro-L-arginine or 10(-3) M N-nitro-L-arginine-methyl ester, inhibitors of L-arginine-derived NO production. SIN-1 (3-morpholino-sydnonimine), an agent which releases NO in aqueous solution, elicited a dose-dependent (0.3-100 microM) vasorelaxation in aortic preparations constricted with 60 mM KCl; the ED50 value for this effect was increased by pretreatment with methylene blue (10 microM) and LY-83,583 (6-(phenylamino)-5,8- quinolinedione; 1 and 3 microM), compounds which inhibit NO-induced stimulation of guanylate cyclase. SIN-1 produced a negative chronotropic effect in right atria; however, this action was not observed at concentrations less than 300 microM and was not antagonized by methylene blue or LY-83,583. 8-Bromo cyclic GMP produced a dose-dependent (10-3000 microM) decrease in KCl-induced tension in aortic rings. In right atria, 8-bromo cyclic GMP elicited a positive chronotropic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetylcholine; Aminoquinolines; Animals; Aorta, Thoracic; Arginine; Cyclic GMP; Guanylate Cyclase; Heart Atria; Heart Rate; In Vitro Techniques; Male; Methylene Blue; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitroarginine; Norepinephrine; Parasympathetic Nervous System; Rats; Rats, Sprague-Dawley; Sympathetic Nervous System; Vasodilator Agents

We observed that N-nitro-L-arginine (NOLA), a nitric oxide biosynthesis inhibitor, exacerbated necrosis in the rabbit heart during ischemia-reperfusion while 3-morpholino-sydnonimine-hydrochloride (SIN-1) (a nitric oxide donor) reduced myocardial damage in the same model. In rabbits undergoing 1-h ligation of the anterior ventricular coronary artery, a single bolus injection of NOLA (30 mg/kg) or continuous infusion of SIN-1 (3 mg/kg) were introduced into the post-ischemic heart immediately before 4-h reperfusion. Against negligible necrosis in 6 sham-operated control animals, and 33.8 (SD 13.5)% necrosis in the area at risk for the saline control group (n = 8), the NOLA-treated group (n = 8) had a necrosis of 44.3 (SD 8.6)% whereas the SIN-1-treated group (n = 10) showed a necrosis of 16.8 (SD 4.9)% (both with p < 0.05 vs saline control group). The pressure-rate index increased in the NOLA-treated group but decreased in the SIN-1-treated group. These data support the contention that a nitric oxide donor is an effective cardioprotector during ischemia-reperfusion in vivo.

Topics: Analysis of Variance; Animals; Arginine; Blood Pressure; Heart; Molsidomine; Myocardial Ischemia; Myocardial Reperfusion; Myocardium; Necrosis; Nitric Oxide; Nitroarginine; Rabbits; Reference Values; Vasodilator Agents

In this study, we analysed the implication of superoxide (O2-.) and nitric oxide (NO.) free radicals and their resulting product peroxynitrite (ONOO-) in the neuronal death induced by the activation of the glutamatergic receptor of the N-methyl-D-aspartate (NMDA) subtype using cultured cerebellar granule cells. The NOl donor SIN-1 (3-morpholinosydnonimine N-ethylcarbamide), at concentrations which produced a much higher guanylate cyclase activation (i.e. NO. concentration) than NMDA, was not neurotoxic and did not increase the NMDA-induced neuronal death. The absence of involvement of NO. in NMDA-induced neuronal death was confirmed by the ineffectiveness of L-NG-nitroarginine (L-Narg) as a neuroprotective compound. Electron paramagnetic resonance (EPR) experiments, using 5,5-dimethyl pyrroline 1-oxide (DMPO) as a spin trap, indicated that NMDA receptor stimulation led to the generation of O2-. from at least 15-30 min. The generation of O2-. by xanthine (XA)-xanthine oxidase (XO) induced a neuronal death similar to that of NMDA. XA-XO-induced neuronal death was suppressed by addition of either superoxide dismutase (SOD) plus catalase (CAT), or DMPO in the incubation medium. In contrast, NMDA-induced neuronal death was widely blocked by DMPO and other spin trap compounds, but not by SOD +/- CAT. XA-XO-induced neuronal death was not potentiated by SIN-1 indicating that ONOO- is not more toxic than O2-. in our neuronal model.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Catalase; Cell Death; Cells, Cultured; Cerebellum; Cyclic GMP; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Mice; Molsidomine; N-Methylaspartate; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Receptors, N-Methyl-D-Aspartate; Superoxide Dismutase; Superoxides; Xanthine Oxidase

Experiments were designed to determine the role of the L-arginine pathway in endothelium-dependent relaxations to vasopressin. The effects of L-arginine analogues NG-nitro-L-arginine (L-NNA), NG-nitro-L-arginine methyl ester (L-NAME), and NG-monomethyl-L-arginine (L-NMMA) on basal and vasopressin-induced activity of nitric oxide synthase were studied in isolated canine basilar arteries. Rings with and without endothelium were suspended for isometric tension recording in Krebs-Ringer bicarbonate solution bubbled with 94% O2-6% CO2 (37 degrees C, pH 7.4). Radioimmunoassay was used to determine the level of guanosine 3',5'-cyclic monophosphate (cGMP). All experiments were performed in the presence of indomethacin, a cyclooxygenase inhibitor. L-NAME and L-NMMA caused endothelium-dependent contractions and inhibited basal production of cGMP. In contrast, L-NNA did not affect basal tone or basal production of cGMP. L-Arginine analogues inhibited relaxations to vasopressin but did not affect relaxations to a nitric oxide donor, molsidomine (SIN-1). The effects of L-NNA, L-NAME, and L-NMMA were reversed in the presence of L-arginine. The relaxations to vasopressin were associated with an increase of cGMP levels in the arterial wall. This effect of vasopressin was inhibited in the presence of L-NNA. These studies suggest that the relaxations to vasopressin are mediated by activation of the endothelial L-arginine pathway, leading to increased production of nitric oxide, with subsequent activation of guanylate cyclase in smooth muscle cells. In canine basilar artery, L-NAME and L-NMMA are nonselective inhibitors of both basal and stimulated production of nitric oxide, whereas L-NNA selectively inhibits vasopressin-induced activation of the L-arginine pathway.

Topics: Animals; Arginine; Basilar Artery; Cyclic GMP; Dogs; Endothelium, Vascular; In Vitro Techniques; Molsidomine; Nitric Oxide; Nitroarginine; Vasodilation; Vasopressins

The nitric oxide donor, SIN-1 and nitric oxide synthase inhibitor, nitro-L-arginine were examined for their effects on energy metabolism using 31P magnetic resonance spectroscopy, and on radiation sensitivity in the transplantable murine tumour, SCCVII/Ha. SIN-1 at 2 mg/kg i.v. reduced Pi/total by 40-50% within 10 min and increased X-ray sensitivity 3 fold, consistent with increased tumour oxygenation. Nitro-L-arginine at 10 mg/kg i.v. increased Pi/total by 250% at 45 min and was maintained for at least 2 hr. Nitro-L-arginine also increased radiation resistance 3-5 fold, consistent with the induction of tumour hypoxia. The results indicate that tumour energy metabolism may be altered through drug induced modification of nitric oxide availability, and that these changes are sufficient to modify tumour sensitivity to X-rays.

Topics: Animals; Arginine; Biological Availability; Cell Hypoxia; Energy Metabolism; Magnetic Resonance Spectroscopy; Mice; Mice, Inbred C3H; Molsidomine; Neoplasm Transplantation; Neoplasms, Experimental; Nitric Oxide; Nitroarginine; Radiation Tolerance

This study was designed to determine vasodilator activities of two endothelium-derived relaxing factors: prostacyclin (PGI2) and nitric oxide (NO) in human umbilical arteries. Isolated vessel segments were contracted by submaximal concentrations of serotonin and bradykinin. These contractions were enhanced after inhibition of prostaglandin formation by the cyclooxygenase inhibitor indomethacin and after removal of the endothelium, both resulting in a pronounced decrease in PGI2 formation. Contractions remained unchanged after treatment of the vessels with nitro-L-arginine, a selective inhibitor of endogenous NO biosynthesis. The efficacy of inhibition of NO biosynthesis was established by a more than 60% reduction in cyclic GMP accumulation. Even inhibition of stimulated NO formation by histamine did not change vascular tone. These data suggest that PGI2 rather than NO is an endothelium-derived relaxing factor in human umbilical arteries.

Topics: Arginine; Bradykinin; Cyclic GMP; Epoprostenol; Female; Histamine; Humans; Iloprost; In Vitro Techniques; Indomethacin; Molsidomine; Muscle Contraction; Nitric Oxide; Nitroarginine; Serotonin; Umbilical Arteries; Vasodilation

The modulating effects of exogenous and endogenous nitric oxide (NO) on the cardiac anaphylactic reaction and eicosanoid release were investigated in isolated perfused sensitized guinea-pig hearts using 3-morpholinosydnonimine (SIN-1), the active metabolite of molsidomine, as NO-donor and NG-nitro-L-arginine (NNA) as an inhibitor of NO biosynthesis. Infusion of SIN-1 (final concentrations in the perfusates 0.3 or 1.0 mmol/l) elevated coronary flow under basal conditions as well as during cardiac anaphylaxis, while NNA (0.1 mmol/l) decreased basal coronary flow and aggravated the anaphylactic coronary constriction. Both drugs did not modify the characteristic biphasic profile of the coronary constriction after antigen challenge with an initial more severe phase followed by a less pronounced long-lasting flow reduction. Neither SIN-1 nor NNA affected spontaneous heart rate. However, while NNA tended to prolong the duration of antigen-induced arrhythmias, SIN-1 (1 mmol/l) had an inhibitory effect. This protection might be related to the increased coronary flow in the presence of SIN-1. SIN-1 inhibited anaphylactic release of cysteinyl-leukotrienes (LT) and 6-keto-prostaglandin (PG) F1 alpha, but did not influence thromboxane (TX) B2 release. On the other hand, NNA (0.1 mmol/l) inhibited anaphylactic release of TXB2, but had only marginal effects on the release of cysteinyl-LT and 6-keto-PGF1 alpha. The results suggest that exogenous and endogenous NO functionally antagonize the effects of vasoconstrictor mediators released after antigen challenge. Additional effects of high concentrations of SIN-1 and NNA on antigen-induced eicosanoid release could modulate the vascular actions of these drugs during cardiac anaphylaxis.

Topics: 6-Ketoprostaglandin F1 alpha; Anaphylaxis; Animals; Antihypertensive Agents; Arginine; Coronary Circulation; Guinea Pigs; Heart; Leukotriene B4; Male; Molsidomine; Nitroarginine; Perfusion; Thromboxane B2; Vasodilator Agents

1. NG-nitro-L-arginine (L-NOARG, 10(-4) M), an inhibitor of nitric oxide (NO) synthesis, had no contractile effect on isolated preparations of rabbit and human corpus cavernosum at baseline tension, but increased tension in preparations contracted by noradrenaline (rabbit 10(-5) M, man 3 x 10(-7)-3 x 10(-6) M) or K+ (rabbit 60 mM). 2. Electrical field stimulation (supramaximal voltage, 0.8 ms pulses, 5 s train duration, 0.5-35 Hz) of rabbit and human corpus cavernosum preparations contracted by noradrenaline (rabbit 10(-5) M, man 3 x 10(-6) M) or endothelin-1 (rabbit 10(-8) M) produced relaxations that were sensitive to tetrodotoxin (10(-6) M), and dependent on the frequency and number of pulses delivered. L-NOARG (10(-6)-10(-4) M), but not NG-nitro-D-arginine (D-NOARG, 10(-6)-10(-4) M), inhibited electrically induced relaxations in a concentration-dependent manner, and at 10(-4) M the relaxations were virtually abolished. L-Arginine (10(-3) M), but not D-arginine (10(-3) M), partly reversed the inhibitory effect of L-NOARG (10(-4) M). In rabbit corpus cavernosum preparations, as with Methylene Blue (3 x 10(-5) M), an inhibitor of the soluble guanylate cyclase, and haemoglobin (10(-5) M), sequestering NO in the extracellular space, significantly reduced electrically evoked relaxations. Scopolamine (10(-6) M) had little or no effect on relaxations induced by electrical field stimulation. 3. Preparations of rabbit and human corpus cavernosum contracted by noradrenaline (rabbit 10(-5) M, man 3 x 10(-6) M) were relaxed by carbachol (10(-9)-10(-4) M) in a concentration-dependent manner. Scopolamine (10(-6) M) and L-NOARG (10(-4) M) abolished, and Methylene Blue (3 x 10(-5) M) and haemoglobin (10(-5) M) greatly reduced, the carbachol-induced relaxation, while D-NOARG (10(-4) M) had no significant effect. 4. In rabbit corpus cavernosum preparations contracted by noradrenaline (10(-5) M), L-NOARG (10(-4) M) had no significant effect on relaxations induced by vasoactive intestinal polypeptide (10(-6) M). 5. SIN-1 (3-morpholino-sydnonimin hydrochloride, 10(-8)-3 x 10(-4) M), which spontaneously liberates NO, relaxed preparations of rabbit and human corpus cavernosum contracted by noradrenaline (rabbit 10(-5) M, man 3 x 10(-6) M) or endothelin-1 (rabbit 10(-8) M, man 3 x 10(-9) M) in a concentration-dependent way.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Animals; Arginine; Electric Stimulation; Humans; Male; Molsidomine; Muscle Contraction; Muscle Relaxation; Nitric Oxide; Nitroarginine; Penis; Rabbits; Synaptic Transmission; Vasodilator Agents

The possibility that calmodulin inhibitors impair the constitutive but not the inducible nitric oxide synthase(s)-mediated inhibitions of tone was investigated in the rat aorta. The endothelium-dependent relaxations evoked by acetylcholine, ATP and the calcium ionophore A23187 (which are mediated by the constitutive nitric oxide synthase) were inhibited by calmodulin inhibitors [calmidazolium, W-7 and (N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide, hydrochloride, fendiline] and by an inhibitor of nitric oxide synthase, nitro L-arginine. Nitro L-arginine but not calmidazolium reduced the inhibitory influence of the endothelium on the concentration-contraction curves evoked by phenylephrine. Treatment of aortic rings without endothelium with interleukin-1 beta inhibited the contractions to phenylephrine by inducing nitric oxide synthase activity. Nitro L-arginine but not calmidazolium restored the contractility of the aortic rings. The relaxations evoked by a donor of nitric oxide, 3-morpholino-sydnonimine, were minimally affected by calmidazolium and nitro L-arginine. The basal tissue content in, and the production of, guanosine 3',5' cyclic monophosphate evoked by acetylcholine in rings with endothelium were inhibited by calmidazolium and nitro L-arginine. The production of cyclic GMP evoked by interleukin-1 beta in rings without endothelium was inhibited by nitro L-arginine but not by calmidazolium. These observations indicate that calmodulin inhibitors inhibit the constitutive but not the inducible nitric oxide synthase(s) in the rat aorta.

Topics: Amino Acid Oxidoreductases; Animals; Aorta; Arginine; Calmodulin; Cyclic GMP; Drug Interactions; Endothelium, Vascular; Fendiline; Imidazoles; Male; Molsidomine; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Inbred Strains; Vasodilator Agents

In conscious rats, the basal forebrain was superfused through a push-pull cannula and the release of acetylcholine was determined in the superfusate. Superfusion with the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine, diminished the release of acetylcholine. Subsequent superfusion with the NO donor, 3-morpholino-sydnonimine, enhanced the release of the neurotransmitter. It is concluded that endogenous NO enhances the release of acetylcholine from its neurons.

Topics: Acetylcholine; Amino Acid Oxidoreductases; Animals; Arginine; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Prosencephalon; Rats

We studied the involvement of the L-arginine-nitric oxide pathway in the changes in cerebrovascular reactivity following hemorrhagic hypotension and retransfusion. Feline middle cerebral arteries were prepared from control animals killed under anesthesia and from anesthetised animals subjected to hemorrhagic hypotension (stepwise bleeding to 90, 70, and 50 mmHg, maintained for 20 min at each level) followed by retransfusion (20 min). Two-mm-long vessel segments were suspended in organ chambers containing Krebs-Henseleit solution (37 degrees C, gassed with 95% O2-5% CO2) for isometric force measurements. Contractions to noradrenaline (norepinephrine), relaxations to acetylcholine, ATP, adenosine, and SIN-1, a nitric oxide donor compound, were compared in the vessels of the control and hemorrhage-subjected animals. Contractile responses to noradrenaline were significantly enhanced after hemorrhage, whereas relaxations to acetylcholine, ATP, and adenosine were significantly reduced. Relaxations to SIN-1, however, remained unchanged. L-Arginine did not cause relaxations in control vessels but relaxed the arteries after hemorrhage and retransfusion. To clarify the involvement of the L-arginine-nitric oxide pathway in these alterations, we studied the effect of exogenous application of L-arginine, the precursor of endothelium-derived relaxing factor (EDRF) and NG-nitro-L-arginine (NOLA), a competitive antagonist of the EDRF-producing enzyme on the vascular responses in vitro. Similar to the effect of hypotension and retransfusion, NOLA enhanced the noradrenaline-induced contractions and inhibited the acetylcholine-induced and purinoceptor-mediated relaxations in the control arteries. In the control vessels in vitro, L-arginine treatment did not modify any contractile or relaxant response. At the same time, in vitro L-arginine treatment inhibited the hemorrhagic hypotension-induced enhancement of the contractions to noradrenaline and restored the diminished relaxations to acetylcholine (but not to ATP or adenosine). In the vessels after hemorrhage, NOLA neither further enhanced the already markedly enhanced noradrenaline-induced contractions nor further inhibited the relaxations caused by ATP and adenosine. In the case of acetylcholine, however, NOLA caused a further inhibition of the relaxations. The effect of in vivo L-Arg infusion (30 mg/kg initial bolus and 10 mg/kg/min infusion) during hemorrhagic hypotension and retransfusion on the in vitro vascular react

Topics: Acetylcholine; Animals; Arginine; Cats; Cerebral Arteries; Endothelium, Vascular; Male; Molsidomine; Muscle, Smooth, Vascular; Nitroarginine; Norepinephrine; Reperfusion; Shock, Hemorrhagic; Vasodilation

Human isolated central (5 to 12 mm) and peripheral (< 2 mm) bronchi were contracted with 3 microM histamine. Relaxations were then evoked by electrical field stimulation (EFS) (1 to 32 Hz, 1 ms, 12 V for 15 s in the presence of indomethacin, atropine, and propranolol). The magnitude, time-course, and frequency-response relationship of these nonadrenergic, noncholinergic (NANC) relaxations were similar in the central and the peripheral airways. NG-Nitro-L-arginine (L-NOARG) (10 microM) inhibited the tetrodotoxin-sensitive NANC relaxations in both central and peripheral bronchi, whereas the stereoisomer D-NOARG was without effect. This inhibition was reversed by L-arginine (1 mM) but not be D-arginine (1 mM). The nitric oxide donor compound, 3-morpholinosydnonimine (SIN-1), was equipotent at relaxing the central and peripheral airways. Vasoactive intestinal peptide (VIP), although it relaxed central airways, was virtually ineffective in relaxing the peripheral airways. In addition, the peptidase, alpha-chymotrypsin, at a concentration that blocked relaxations to VIP, was without effect on NANC relaxations in the central bronchi. The results support the following hypotheses: (1) both central and peripheral airways receive nonadrenergic relaxant innervation; (2) the relaxant response to electrical stimulation of this system is dependent on a pathway involving L-arginine; and (3) the relaxant response does not appear to involve VIP, but it may involve the production of nitric oxide.

Topics: Arginine; Bronchi; Chymotrypsin; Electric Stimulation; Humans; In Vitro Techniques; Molsidomine; Muscle Relaxation; Nitroarginine; Stereoisomerism; Vasoactive Intestinal Peptide; Vasodilator Agents

1. Previous studies, demonstrated that endothelium-dependent relaxations which are resistant to nitro-L-arginine (an inhibitor of nitric oxide synthase) are accompanied by membrane hyperpolarization in the porcine coronary artery. The present experiments were designed to characterize further this type of endothelium-dependent relaxation in response to bradykinin by measuring isometric force in isolated rings of that artery. The experiments were performed in the presence of indomethacin to rule out vasoactive prostanoids. 2. Bradykinin induced comparable endothelium-dependent relaxations of proximal and distal rings of porcine coronary arteries contracted with prostaglandin F2 alpha in the presence of nitro-L-arginine. 3. Bradykinin and SIN 1 (a donor of nitric oxide) reduced contractions induced by prostaglandin F2 alpha in an additive fashion in the presence of nitro-L-arginine. 4. Bradykinin (in the presence of nitro-L-arginine) relaxed the tissues contracted with tetraethylammonium, prostaglandin F2 alpha, phorbol 12, 13-diacetate or endothelin, with similar pD2 values. 5. The time course of the relaxations induced by bradykinin (in the presence of nitro-L-arginine) and UK14304 (an alpha 2-adrenoceptor agonist, in the absence of the inhibitor of nitric oxide synthase) were comparable. 6. These results suggest that, in the porcine coronary artery, nitro-L-arginine-resistant relaxations (a) are distributed similarly in the proximal and distal parts of the artery, (b) contribute to inhibition of vascular smooth muscle with nitric oxide in an additive fashion, (c) occur during contractions induced by various contractile agents and (d) do not precede those mediated by nitric oxide.

Topics: Animals; Arginine; Bradykinin; Coronary Vessels; Dinoprost; Endothelium, Vascular; In Vitro Techniques; Molsidomine; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Swine; Vasodilation; Vasodilator Agents

In isolated perfused ovalbumin-sensitized guinea-pig hearts modulating effects of nitric oxide (NO) on cardiac function and eicosanoid release were investigated. While the NO-donor SIN-1 exhibited a protective effect during cardiac anaphylaxis, inhibition of NO biosynthesis by NNA or NMMA aggravated anaphylactic changes of cardiac functions. Exogenous and endogenous NO seems to functionally antagonize the effects of vasoconstrictor mediators released during the anaphylactic reaction. In addition, inhibition of cysteinyl-leukotriene (cys-LT) release could contribute to the protective effect of SIN-1 observed.

Topics: Anaphylaxis; Animals; Arginine; Coronary Circulation; Eicosanoids; Guinea Pigs; Heart; Heart Rate; In Vitro Techniques; Male; Molsidomine; Myocardium; Nitroarginine; omega-N-Methylarginine; Ovalbumin

1. The interactions between carbenoxolone and nitric oxide (NO) were examined by investigating their effects on human platelet aggregation, on rat aortic strips precontracted by phenylephrine and on protection of rat gastric mucosa against ethanol-induced injury. 2. Carbenoxolone (100-300 microM) caused a significant and concentration-dependent potentiation of rat peritoneal neutrophil (RPN)- 3-morpholino-syndnonimine (SIN-1)- or iloprost-induced inhibition of platelet aggregation. Higher concentrations (500 microM) of carbenoxolone alone markedly inhibited platelet aggregation. Pretreatment with carbenoxolone (100-300 microM) antagonized the reversal of the RPN- or SIN-1-induced antiaggregatory effect by oxyhaemoglobin (10 microM). 3. Rat aortic strips with intact endothelium precontracted by phenylephrine (0.1-0.3 microM) were relaxed by carbenoxolone (100-300 microM) in a concentration-dependent manner. Relaxations were abolished by mechanical removal of the endothelium or by incubation with methylene blue (10 microM) or NG-nitro-L-arginine (L-NNA, 100 microM). Sodium nitroprusside (10 nM)-induced relaxations of endothelium-denuded rat aortic strips were potentiated by carbenoxolone (100 microM). . The carbenoxolone (200 mg kg-1, p.o.)-induced gastroprotection against ethanol was antagonized by L-NNA (5-40 mg kg-1) in a dose-dependent manner. Pretreatment of rats with indomethacin (10 mg kg-1, s.c.) increased the effect of L-NNA. 5. The results suggest that the activity of carbenoxolone in the experimental systems tested is due to phosphodiesterase inhibition, although radical scavenging properties of the drug could contribute to some of the effects observed. In the rat gastric mucosa both increased prostaglandin levels and effects on the NO system could contribute to the protective action of carbenoxolone.

Topics: Animals; Aorta; Arginine; Carbenoxolone; Gastric Mucosa; Humans; Iloprost; In Vitro Techniques; Male; Methylene Blue; Molsidomine; Muscle Relaxation; Muscle Tonus; Neutrophils; Nitric Oxide; Nitroarginine; Nitroprusside; Oxyhemoglobins; Rats; Rats, Inbred Strains; Stomach Ulcer; Vasodilator Agents