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Inhibitor NG (inhibitor + ng)
Kinds of Inhibitor NG Selected AbstractsSystemic nitric oxide clamping in normal humans guided by total peripheral resistanceACTA PHYSIOLOGICA, Issue 2 2010J. A. Simonsen Abstract Aim:, We wanted to stabilize the availability of nitric oxide (NO) at levels compatible with normal systemic haemodynamics to provide a model for studies of complex regulations in the absence of changes in NO levels. Methods:, Normal volunteers (23,28 years) were infused i.v. with the nitric oxide synthase (NOS) inhibitor NG -nitro- l -arginine methyl ester (l -NAME) at 0.5 mg kg,1 h,1. One hour later, the NO donor sodium nitroprusside (SNP) was co-infused in doses eliminating the haemodynamic effects of l -NAME. Haemodynamic measurements included blood pressure (MABP) and cardiac output (CO) by impedance cardiography. Results:,l -NAME increased MABP and total peripheral resistance (TPR, 1.02 ± 0.05 to 1.36 ± 0.07 mmHg s mL,1, mean ± SEM, P < 0.001). With SNP, TPR fell to a stable value slightly below control (0.92 ± 0.05 mmHg s mL,1, P < 0.05). CO decreased with l -NAME (5.8 ± 0.3 to 4.7 ± 0.3 L min,1, P < 0.01) and returned to control when SNP was added (6.0 ± 0.3 L min,1). A decrease in plasma noradrenaline (42%, P < 0.01) during l -NAME administration was completely reversed by SNP. Plasma renin activity decreased during l -NAME administration and returned towards normal after addition of SNP. In contrast, plasma aldosterone was increased by l -NAME and remained elevated. Conclusions:, Concomitant NOS inhibition and NO donor administration can be adjusted to maintain TPR at control level for hours. This approach may be useful in protocols in which stabilization of the peripheral supply of NO is required. However, the dissociation between renin and aldosterone secretion needs further investigation. [source] Quinolinic acid modulates the activity of src family kinases in rat striatum: in vivo and in vitro studiesJOURNAL OF NEUROCHEMISTRY, Issue 5 2006Alessio Metere Abstract Quinolinic acid (QA) has been shown to evoke neurotoxic events via NMDA receptor (NMDAR) overactivation and oxidative stress. NMDARs are particularly vulnerable to free radicals, which can modulate protein tyrosine kinase (PTK) and phosphotyrosine phosphatase (PTP) activities. The src family of tyrosine kinases are associated with the NMDAR complex and regulate NMDA channel function. Because QA is an NMDAR agonist as well as a pro-oxidant agent, we investigated whether it may affect the activity of PTKs and PTPs in vivo and in vitro. In synaptosomes prepared from striata dissected 15 min, 30 min or 15 days after bilateral injection of QA we observed modulation of the phosphotyrosine pattern; a significant decrease in PTP activity; and a sustained increase in c-src and lyn activity at 15 and 30 min after treatment with QA, followed by a decrease 2 weeks later. Striatal synaptosomes treated in vitro with QA showed time- and dose-dependent modulation of c-src and lyn kinase activities. Moreover, the nitric oxide synthase inhibitor NG -nitro- l -arginine-methyl ester, the NMDAR antagonist d -2-amino-5-phosphonovaleric acid and pyruvate suppressed the QA-induced modulation of c-src activity. These findings suggest a novel feature of QA in regulating src kinase activity through the formation of reactive radical species and/or NMDAR overactivation. [source] Prothrombin kringle-2 induces death of mesencephalic dopaminergic neurons in vivo and in vitro via microglial activationJOURNAL OF NEUROSCIENCE RESEARCH, Issue 7 2010Sang Ryong Kim Abstract We have shown that prothrombin kringle-2 (pKr-2), a domain of human prothrombin distinct from thrombin could activate cultured rat brain microglia in vitro. However, little is known whether pKr-2-induced microglial activation could cause neurotoxicity on dopaminergic (DA) neurons in vivo. To address this question, pKr-2 was injected into the rat substantia nigra (SN). Tyrosine hydroxylase (TH) immunohistochemistry experiments demonstrate significant loss of DA neurons seven days after injection of pKr-2. In parallel, pKr-2-activated microglia were detected in the SN with OX-42 and OX-6 immunohistochemistry. Reverse transcription PCR and double-label immunohistochemistry revealed that activated microglia in vivo exhibit early and transient expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and several proinflammatory cytokines. The pKr-2-induced loss of SN DA neurons was partially inhibited by the NOS inhibitor NG -nitro-L-arginine methyl ester hydrochloride, and the COX-2 inhibitor DuP-697. Extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase were activated in the SN as early as 1 hr after pKr-2 injection, and localized within microglia. Inhibition of these kinases led to attenuation of mRNA expression of iNOS, COX-2 and several proinflammatory cytokines, and rescue of DA neurons in the SN. Intriguingly, following treatment with pKr-2 in vitro, neurotoxicity was detected exclusively in co-cultures of mesencephalic neurons and microglia, but not microglia-free neuron-enriched mesencephalic cultures, indicating that microglia are required for pKr-2 neurotoxicity. Our results strongly suggest that microglia activated by endogenous compound(s), such as pKr-2, are implicated in the DA neuronal cell death in the SN. © 2009 Wiley-Liss, Inc. [source] Modulation of the cGMP signaling pathway by melatonin in pancreatic , -cellsJOURNAL OF PINEAL RESEARCH, Issue 2 2009Ina Stumpf Abstract:, Melatonin influences the second messenger cyclic guanosine 3,,5,-monophosphate (cGMP) signaling pathway in pancreatic , -cells via a receptor-mediated mechanism. In the present study, it was determined how the regulation of cGMP concentrations by melatonin proceeds. The results provide evidence that melatonin acts via the soluble guanylate cyclase (sGC), as molecular investigations demonstrated that long-term incubation with melatonin significantly reduced the expression levels of the sGC mRNA in rat insulinoma , -cells (INS1) cells, whereas mRNA expression of membrane guanylate cyclases was unaffected. Incubation with melatonin abolished the S-nitrosoacetyl penicillamine-induced increase of cGMP concentrations in INS1 cells. In addition, the cGMP-inhibitory effect of melatonin was reversed by preincubation with the sGC inhibitors 1H-(1,2,4)oxadiazolo(4,3- ,)quinoxalin-1-one and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one. Nitric oxide (NO) production was not influenced after 1 hr of melatonin application, but was influenced after a 4 hr incubation period. Preincubation of INS1 cells with the NO synthase inhibitor NG -monomethyl- l -arginine did not abolish the cGMP-inhibitory effect of melatonin. Transcripts of cyclic nucleotide-gated (CNG) channels were significantly reduced after melatonin treatment in a dose-dependent manner, indicating the involvement of these channels in mediating the melatonin effect in INS1 cells. The results of this study demonstrate that melatonin mediates its inhibitory effect on cGMP concentrations in pancreatic , -cells by inhibiting the sGC, but does not influence NO concentration or NO synthase activity in short-term incubation experiments. In addition, it was demonstrated that melatonin is involved in modulation of CNG channel mRNA. [source] Nitric Oxide Synthesis Inhibition Attenuates Conditioned Reinstatement of Ethanol-Seeking, but Not the Primary Reinforcing Effects of EthanolALCOHOLISM, Issue 8 2004Xiu Liu Background: Nitric oxide (NO) signaling has been implicated in regulating aspects of the reinforcing and addictive actions of cocaine. These experiments were designed to examine whether NO-dependent neurotransmission also participates in mediating the addictive actions of another drug of abuse, ethanol, with emphasis on both the primary reinforcing effects of ethanol and the incentive motivational effects of ethanol-related contextual stimuli. Methods: Male Wistar rats were operantly trained to orally self-administer 10% (w/v) ethanol in daily 30-min sessions and to associate distinct discriminative stimuli with the availability of ethanol (S+) versus nonreward (S,). Rats were treated with the NO synthase inhibitor NG -nitro-l-arginine methyl ester (l-NAME; 0, 10, or 40 mg/kg intraperitoneally) 30 min before self-administration tests that were conducted after establishment of stable levels of daily ethanol intake and conditioned reinstatement tests that were performed after extinction of ethanol-maintained operant responding. Results: l-NAME did not alter the primary reinforcing effects of ethanol in self-administration tests. In contrast, l-NAME dose-dependently attenuated the recovery of extinguished responding induced by the ethanol S+ in the absence of ethanol availability during reinstatement tests. Conclusions: These results suggest that the NO system does not play a role in behavior reinforced directly by ethanol. However, the results implicate NO-dependent neurotransmission in alcohol-seeking responses elicited by drug-related contextual stimuli. [source] Differences in circular muscle contraction and peristaltic motor inhibition caused by tachykinin NK1 receptor agonists in the guinea-pig small intestineNEUROGASTROENTEROLOGY & MOTILITY, Issue 2 2000Shahbazian The tachykinin NK1 receptor agonist substance P methyl ester (SPOME) impedes intestinal peristalsis by releasing nitric oxide (NO) from inhibitory motor neurones. Since NK1 receptor agonists differ in their receptor interaction, we set out to compare a range of NK1 receptor agonists including SPOME, septide and GR-73 632 in their effects on propulsive peristalsis and circular muscle activity in the guinea-pig isolated small intestine. SPOME (100,300 n M) inhibited peristalsis by a rise of the pressure threshold at which peristaltic waves were triggered, whereas septide and GR-73 632 (30,300 n M) interrupted peristalsis by causing circular muscle spasms. Separate experiments showed that all three NK1 receptor agonists caused contraction of the circular muscle, which was enhanced by the NO synthase inhibitor NG -nitro- L -arginine methyl ester (300 ,M) and the P2X purinoceptor antagonist suramin (300 ,M). In contrast, tetrodotoxin (300 n M) augmented the contractile effect of septide and GR-73 632 but not that of SPOME. It is concluded that the motor response to NK1 receptor agonists involves release of NO and adenosine triphosphate from inhibitory motor neurones. However, the NK1 receptor agonists differ in the mechanism by which they cause inhibitory transmitter release, which corresponds to differences in their antiperistaltic action. [source] Pre-junctional ,2 -adrenoceptors modulation of the nitrergic transmission in the pig urinary bladder neck,NEUROUROLOGY AND URODYNAMICS, Issue 4 2007Medardo Hernández Abstract Aims To investigate the nitric oxide (NO)-mediated nerve relaxation and its possible modulation by pre-junctional ,2 -adrenoceptors in the pig urinary bladder neck. Methods Urothelium-denuded bladder neck strips were dissected, and mounted in isolated organ baths containing a physiological saline solution (PSS) at 37°C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (electrical field stimulation [EFS]) or exogenously applied NO were carried out on strips pre-contracted with 1 µM phenylephrine (PhE) and treated with guanethidine (10 µM) and atropine (0.1 µM), to block noradrenergic neurotransmission and muscarinic receptors, respectively. Results EFS (0.2,1 Hz, 1 msec duration, 20 sec trains, current output adjusted to 75 mA) evoked frequency-dependent relaxations which were abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 µM). These responses were potently reduced by the nitric oxide synthase (NOS) inhibitor NG -nitro- L -arginine (L-NOARG, 30 µM) and further reversed by the NO synthesis substrate L -arginine (L-ARG, 3 mM). The ,2 -adrenoceptor agonist BHT-920 (2 µM) reduced the electrically evoked relaxations, its effectiveness being higher on the responses induced by low frequency stimulation. BHT-920-elicited reductions were fully reversed by the ,2 -adrenoceptor antagonist rauwolscine (RAW, 1 µM). Exogenous NO (1 µM,1 mM) induced concentration-dependent relaxations which were not modified by BHT-920, thus eliminating a possible post-junctional modulation. Conclusions These results indicate that NO is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission in the pig urinary bladder neck, the release of NO from intramural nerves being modulated by pre-junctional ,2 -adrenoceptor stimulation. Neurourol. Urodynam. 26:578,583, 2007. © 2007 Wiley-Liss, Inc. [source] Cytokinin- and auxin-induced stomatal opening is related to the change of nitric oxide levels in guard cells in broad beanPHYSIOLOGIA PLANTARUM, Issue 3 2006She Xiao-Ping The relationship between cytokinin- and auxin-induced stomatal opening and nitric oxide (NO) levels in guard cells in broad bean was studied. Results indicate that cytokinins and auxins reduced the levels of NO in guard cells and induced stomatal opening in darkness. In addition, cytokinins not only reduced NO levels in guard cells caused by sodium nitroprusside (SNP) in light but also abolished NO that had been generated by dark, and then promoted the closed stomata reopening, as did NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. However, unlike cytokinins, auxins not only had incapability to reduce NO levels by SNP but also could not abolish NO having been generated by dark, so auxins could not promote the closed stomata to reopen. The above-mentioned effects of auxins were similar to that of nitric oxide synthase (enzyme commission 1.14.13.39) inhibitor NG -nitro- l -Arg-methyl ester. Hence, it is concluded that cytokinins reduced probably the levels of NO in guard cells via scavenging, and auxins reduced NO levels through restraining NO generation in all probability, and then induced stomatal opening in darkness. [source] Direct evidence of nitric oxide release from neuronal nitric oxide synthase activation in the left ventricle as a result of cervical vagus nerve stimulationTHE JOURNAL OF PHYSIOLOGY, Issue 12 2009Kieran E. Brack Information regarding vagal innervation in the cardiac ventricle is limited and the direct effect of vagal stimulation on ventricular myocardial function is controversial. We have recently provided indirect evidence that the anti-fibrillatory effect of vagus nerve stimulation on the ventricle is mediated by nitric oxide (NO). The aim of this study was to provide direct evidence for the release of nitric oxide in the cardiac ventricle during stimulation of the efferent parasympathetic fibres of the cervical vagus nerve. The isolated innervated rabbit heart was employed with the use of the NO fluorescent indicator 4,5-diaminofluorescein diacetate (DAF-2 DA) during stimulation of the cervical vagus nerves and acetylcholine perfusion in the absence and presence of the non-specific NO synthase inhibitor NG -nito- l- arginine (l- NNA) and the neuronal NO synthase selective inhibitor 1-(2-trifluormethylphenyl)imidazole (TRIM). Using the novel fluorescence method in the beating heart, we have shown that NO-dependent fluorescence is increased by 0.92 ± 0.26, 1.20 ± 0.30 and 1.91 ± 0.27% (during low, medium and high frequency, respectively) in the ventricle in a stimulation frequency-dependent manner during vagus nerve stimulation, with comparable increases seen during separate stimulation of the left and right cervical vagus nerves. Background fluorescence is reduced during perfusion with l- NNA and the increase in fluorescence during high frequency vagal stimulation is inhibited during perfusion with both l- NNA (1.97 ± 0.35% increase before l- NNA, 0.00 ± 0.02% during l- NNA) and TRIM (1.78 ± 0.18% increase before TRIM, ,0.11 ± 0.08% during TRIM). Perfusion with 0.1 ,m acetylcholine increased NO fluorescence by 0.76 ± 0.09% which was blocked by l- NNA (change of 0.00 ± 0.03%) but not TRIM (increase of 0.82 ± 0.21%). Activation of cardiac parasympathetic efferent nerve fibres by stimulation of the cervical vagus is associated with NO production and release in the ventricle of the rabbit, via the neuronal isoform of nitric oxide synthase. [source] The effects of selective phosphodiesterase III and V inhibitors on adrenergic and non-adrenergic, non-cholinergic relaxation responses of guinea-pig pulmonary arteriesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2003A. Tasatargil Summary 1 The aim of the present study was to investigate the role of several possible neurotransmitters in mediating non-adrenergic, non-cholinergic (NANC) relaxation, and the effects of phosphodiesterase (PDE) III and V inhibitors on adrenergic and NANC relaxation in branch pulmonary artery (PA) of guinea-pig. 2 Under the NANC conditions, electrical field stimulation (EFS, 60 V, 0.2 ms, 20 Hz) induced a tetrodotoxin-sensitive relaxation of the histamine-precontracted PA rings. The nitric oxide (NO) synthase inhibitor NG -nitro- l -arginine methyl ester (l -NAME, 10,4 m) and the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10,5 m) partially inhibited the EFS-induced relaxation. The inhibitory effect of l -NAME was reversed completely by l -arginine (10,3 m), but not d -arginine (10,3 m). 3 This NANC relaxation was attenuated by 8-phenyltheophylline (10,5 m), a P1 -purinoceptor antagonist. 4 The NANC response was potentiated by 10,6 m zaprinast, a type V PDE inhibitor, but was unaffected by 3 × 10,6 m milrinone, a type III PDE inhibitor. 5 Sodium nitroprusside (SNP) caused a concentration-dependent vasodilator effect which was potentiated by zaprinast, but unaffected by milrinone. Moreover, the effect of combination of zaprinast with milrinone was not significantly different from that observed with zaprinast alone. 6 Isoprenaline produced a concentration-dependent vasodilatation in branch PA of guinea-pig which was potentiated by both zaprinast and milrinone, the efficacy of milrinone being greater than zaprinast. 7 These results suggest that both nitrergic and purinergic pathways are involved in mediating the NANC relaxation in branch PA of guinea-pig. The combination of PDE III or V inhibitors with vasorelaxant drugs may be a hopeful approach for the treatment of pulmonary hypertension. [source] Reciprocal regulation of human soluble and particulate guanylate cyclases in vivoBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2006M Madhani Background & purpose: We demonstrated previously that reciprocal regulation of soluble (sGC) and particulate (pGC) guanylate cyclases by NO and natriuretic peptides coordinates cyclic cGMP-mediated vasodilatation in vitro. Herein, we investigated whether such an interaction contributes to vascular homeostasis in mice and humans in vivo. Experimental approach: Mean arterial blood pressure (MABP) changes in anaesthetized mice were monitored in response to i.v. administration of cGMP- and cAMP-dependent vasodilators in wild-type (WT), endothelial NO synthase (eNOS) and natriuretic peptide receptor (NPR)-A knockout mice. Forearm blood flow (FBF) in response to intra-brachial infusion of ANP (25, 50, 100, 200 pmol min -1) in the absence and presence of the NOS inhibitor NG -methyl-L-arginine (L-NMA; 4 ,mol min -1) and the control constrictor noradrenaline (240 pmol min -1) was assessed in healthy volunteers. Key results: Sodium nitroprusside (SNP; NO-donor) and atrial natriuretic peptide (ANP) produced dose-dependent reductions in MABP in WT animals that were significantly enhanced in eNOS KO mice. In NPR-A K mice, SNP produced a dose-dependent reduction in MABP that was significantly greater than that in WT mice. Responsiveness to the cAMP-dependent vasodilator epoprostenol was similar in WT, eNOS KO and NPR-A KO animals. ANP caused vasodilatation of the forearm resistance vasculature that was significantly greater in individuals lacking endothelium-derived NO (i.e. L-NMA treated). Conclusions & implications: These data demonstrate that crosstalk occurs between the NO-sGC and ANP-pGC pathways to regulate cGMP-dependent vasodilatation in vivo in both mice and humans. These findings have implications for understanding the link between natriuretic peptide activity and cardiovascular risk. British Journal of Pharmacology (2006) 149, 797,801. doi:10.1038/sj.bjp.0706920 [source] Evidence for VIP1/PACAP receptors in the afferent pathway mediating surgery-induced fundic relaxation in the ratBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2000G E Boeckxstaens We previously reported activation of an inhibitory adrenergic and a non-adrenergic non-cholinergic (NANC) pathway during abdominal surgery relaxing the rat gastric fundus. In the present study, we investigated the possible role of nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) in the NANC part of the surgery-induced fundic relaxation. The effect of the NO biosynthesis inhibitor NG -nitro- L -arginine (L -NOARG), the non-selective VIP receptor antagonist [D -p-Cl-Phe6,Leu17]-VIP and the selective VIP1 receptor antagonist [Acetyl-His1,D -Phe2,Lys15,Arg16,Leu17]-VIP was investigated on the non-adrenergic fundic relaxation induced by manipulation of the small intestine followed by resection of the caecum. Guanethidine partly reduced the manipulation-induced fundic relaxation. Addition of L -NOARG reduced this non-adrenergic component, whereas the non-selective VIP receptor antagonist had no significant effect. Combination of L -NOARG and the non-selective VIP antagonist however further reduced the relaxation to manipulation. The selective VIP1 receptor antagonist reduced the mean and maximal relaxation induced by abdominal surgery in the presence of guanethidine. When combined with L -NOARG, the relaxation of the gastric fundus was almost completely abolished. The VIP1 receptor antagonist alone had no significant effect on the mean and maximal relaxation, but enhanced recovery of fundic tone. In conclusion, as VIP1 receptors are not present in the rat gastric fundus, these results suggest that the NANC inhibitory pathway activated during abdominal surgery involves VIP1 receptors, most likely in the afferent limb. The inhibitory neurotransmitters released at the level of the gastric fundus smooth muscle are NO and a substance different from VIP. British Journal of Pharmacology (2000) 131, 705,710; doi:10.1038/sj.bjp.0703625 [source] NG -NITRO- l -ARGININE METHYL ESTER POTENTIATES ANAPHYLACTIC VENOCONSTRICTION IN RAT PERFUSED LIVERSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2006Toshishige Shibamoto SUMMARY 1The effects of the nitric oxide (NO) synthase inhibitor NG -nitro- l -arginine methyl ester (l -NAME) on anaphylaxis-induced venoconstriction were examined in rat isolated livers perfused with blood-free solutions in order to clarify the role of NO in anaphylactic venoconstriction. 2Rats were sensitized with ovalbumin (1 mg) and, 2 weeks later, livers were excised and perfused portally in a recirculating manner at a constant flow with Krebs',Henseleit solution. The antigen (ovalbumin; 0.1 mg) was injected into the reservoir 10 min after pretreatment with l-NAME (100 mmol/L) or d -NAME (100 mmol/L) and changes in portal vein pressure (Ppv), hepatic vein pressure (Phv) and perfusate flow were monitored. In addition, concentrations of the stable metabolites of NO ( and ) were determined in the perfusate using an HPLC,Griess system. 3The antigen caused hepatic venoconstriction, as evidenced by an increase in Ppv from a mean (SEM) baseline value of 7.7 ± 0.1 cmH2O to a peak of 21.4 ± 1.1 cmH2O at 3 min in d -NAME-pretreated livers. Pretreatment with l-NAME augmented anaphylactic venoconstriction, as reflected by a higher Ppv (27.4 ± 0.8 cmH2O) after antigen than observed following d -NAME pretreatment. The addition of l -arginine, a precursor for the synthesis of NO, reversed the augmentation of anaphylactic venoconstricion by l -NAME. This suggests that hepatic anaphylaxis increased the production of NO, which consequently attenuated anaphylactic venoconstriction. However, perfusate NOx levels did not increase significantly after antigen in livers pretreated with either l -NAME or d -NAME. 4In conclusion, l -NAME potentiates rat anaphylactic hepatic venoconstriction, suggesting that NO contributes to the attenuation of the venoconstriction. However, this functional evidence was not accompanied by corresponding changes in perfusate NOx concentrations. [source] HIGH GLUCOSE-INDUCED HUMAN UMBILICAL VEIN ENDOTHELIAL CELL HYPERPERMEABILITY IS DEPENDENT ON PROTEIN KINASE C ACTIVATION AND INDEPENDENT OF THE Ca2+,NITRIC OXIDE SIGNALLING PATHWAYCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2005Lei Dang SUMMARY 1.,Endothelial barrier dysfunction plays a pivotal role in the pathogenesis of diabetic vascular complications. The precise molecular mechanisms by which hyperglycaemia causes the increased permeability in endothelial cells are not yet well understood. In the present study, we investigated whether high concentrations of glucose induce endothelial permeability through the activation of protein kinase C (PKC) and/or the calcium,nitric oxide (NO) signalling pathway in human umbilical vein endothelial cells (HUVEC). 2.,Endothelial permeability was measured by albumin diffusion across endothelial monolayers under the stimuli of high glucose (HG; 20 mmol/L), 100 nmol/L phorbol-myristate-acetate (PMA) or 100 nmol/L histamine. The intracellular calcium concentration ([Ca2+]i) was detected in HUVEC using the fluorescent probe fura-2 AM. The effects of PKC inhibitors (LY379196 and hypocrellin A) and the NO synthase (NOS) inhibitor NG -monomethyl- l -arginine (l -NMMA) on endothelial permeability and [Ca2+]i were determined. 3.,High glucose and PMA increased endothelial permeability associated with decreased [Ca2+]i, whereas histamine triggered significant increases in endothelial permeability, accompanied by increases in [Ca2+]i in HUVEC. Hypocrellin A (HA) and LY379196 reversed both HG- and histamine-induced endothelial permeability. The NOS inhibitor l -NMMA only abolished histamine- and not HG-induced endothelial permeability. Neither LY379196, HA nor l -NMMA had any significant effects on alterations in [Ca2+]i caused by HG and histamine. 4.,These results indicate that increased endothelial permeability in HUVEC induced by HG is dependent on PKC activity and is independent of the [Ca2+]i,NO pathway. Increased endothelial permeability due to other inflammatory factors, such as histamine, may also be mediated by the PKC pathway. Thus, PKC inhibitors would be a potential therapeutic approach to endothelial dysfunction induced by hyperglycaemia, as well as other inflammatory factors, in diabetes. [source] INVOLVEMENT OF N -METHYL- d -ASPARTATE RECEPTORS and NITRIC OXIDE IN THE ROSTRAL VENTROMEDIAL MEDULLA IN MODULATING MORPHINE PAIN-INHIBITORY SIGNALS FROM THE PERIAQUEDUCTAL GREY MATTER IN RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2005Kazem Javanmardi SUMMARY 1.,Supraspinal opioid antinociception is mediated, in part, by connections between the periaqueductal grey (PAG) and the rostral ventromedial medulla (RVM). Morphine antinociception from the PAG is decreased by serotonin, N -methyl- d -aspartate (NMDA) and opioid receptor antagonists administered into the RVM. Because the brain isoform of nitric oxide synthase (NOS) is also prominent in the RVM, the present study was designed to evaluate the effects of microinjection of the non-selective NOS inhibitor NG -nitro- l -arginine methyl ester (l -NAME) and the non-competitive NMDA receptor antagonist MK-801 into the RVM on PAG morphine antinociception and their potential interactions, as measured by the tail-flick test. 2.,Rats were anaesthetized with sodium pentobarbital and then special cannulas were inserted stereotaxically into the RVM and PAG. After 1 week recovery, the effects of microinjection of MK-801 and l -NAME into the RVM and their interactions in altering PAG morphine (2.5 µg) antinociception elicited from the PAG were assessed. 3.,Mesencephalic morphine antinociception was significantly reduced after pretreatment with l -NAME (0.6,1.3 µmol) or MK-801 (0.8 nmol). The reduction in mesencephalic morphine antinociception when MK-801 (0.8 nmol) and l -NAME (1 µmol) were microinjected sequentially into the RVM was not significantly different from the effects of MK-801 (0.8 nmol) or l -NAME (1 µmol) administered alone. 4.,These data imply that NMDA receptors and nitric oxide production in the RVM modulate the transmission of opioid pain-inhibitory signals from the PAG. [source] Effects Of Nitric Oxide Synthase Inhibition And Low-Salt Diet On Blood Pressure And Mesenteric Resistance Artery Remodelling In Genetically Hypertensive RatsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2001Janet M Ledingham SUMMARY 1. Nitric oxide synthase (NOS)-inhibited genetically hypertensive (GH) rats on normal and low-sodium diets were additionally given valsartan or felodipine to establish whether low-Na intake would have extra beneficial effects on blood pressure and cardiovascular structure. 2. Male GH rats on normal or low-Na diets were treated with the NOS inhibitor NG -nitro- L -arginine methyl ester (L -NAME) from the age of 7 to 12 weeks and were given either valsartan (10 mg/kg per day) or felodipine (30 mg/kg per day). 3. Systolic blood pressure (SBP; tail-cuff) was measured weekly. At 12 weeks of age, mesenteric resistance arteries (MRA) were fixed by perfusion and embedded in Technovit (Heraeus Kulzer GmbH, Werheim, Germany). Serial sections were cut and stained. Stereological analysis was used to obtain MRA media width, lumen diameter, ratio of media width/lumen diameter (M/L) and medial cross-sectional area (CSA). Left ventricular (LV) mass was determined. 4. In GH L -NAME-treated rats on a normal diet, SBP was significantly reduced (P < 0.001) by valsartan and felodipine, as was LV mass (valsartan P < 0.001; felodipine P < 0.05). A low-Na diet with valsartan caused a further fall in SBP (P < 0.01) but, with felodipine, SBP increased in rats on a low-Na diet (P < 0.05). 5. Valsartan with the low-Na diet had no further effect on LV mass, but the felodipine-treated group on a low-Na diet had a lower LV mass (P < 0.05) than rats on a normal diet. 6. In MRA from the GH L -NAME + valsartan-treated group, there was hypotrophic inward remodelling; the M/L ratio was reduced (P < 0.001) compared with GH L -NAME-treated rats. The lumen was outwardly remodelled in the group on the low-Na diet. 7. The GH L -NAME + felodipine-treated group showed hypotrophic outward remodelling and a reduction in M/L ratio compared with the GH L -NAME-treated group (P < 0.001). A low-Na diet had no further effect on MRA. 8. A low-Na diet + valsartan had beneficial effects on SBP and MRA, where outward remodelling of the lumen occurred and, thus, resistance was reduced. In contrast, felodipine with a low-Na diet increased SBP, reduced LV mass and had no effect on MRA structure. Valsartan treatment with a low-Na diet confers extra benefits on blood pressure and MRA structure. [source] Effect Of Anti-Oxidant Treatment And Cholesterol Lowering On Resting Arterial Tone, Metabolic Vasodilation And Endothelial Function In The Human Forearm: A Randomized, Placebo-Controlled StudyCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2001Stephen J Duffy SUMMARY 1. The aim of the present study was to determine whether anti-oxidant therapy with vitamin E and/or cholesterol-lowering therapy with simvastatin would augment resting forearm blood flow (FBF) and metabolic vasodilation in response to exercise and improve endothelial function in young patients with hypercholesterolaemia. 2. Endothelium-dependent and -independent, nitric oxide (NO)-mediated vasodilation have been shown to be impaired in young, otherwise healthy subjects with hypercholesterolaemia. Recent experimental and clinical studies suggest that vascular function may be improved with anti-oxidant or cholesterol- lowering therapy, although these treatments may be synergistic. 3. We compared FBF at rest, in response to isotonic exercise, the endothelium-dependent vasodilator acetylcholine (ACh), the endothelium-independent vasodilator sodium nitroprusside (SNP) and the NO synthase inhibitor NG -monomethyl- L -arginine (L -NMMA) in 26 young, otherwise healthy volunteers (mean (±SD) age 29±7 years; 14 female, 12 male) with hypercholesterolaemia, before and after 6 months treatment with vitamin E, simvastatin and/or placebo. Treatment was randomized, double-blinded in a 2 × 2 factorial design. Forearm blood flow was measured using venous occlusion plethysmography. 4. Vitamin E therapy increased plasma ,-tocopherol from 39.5±9.6 to 75.7±33.8 ,mol/L (P < 0.001). Simvastatin reduced total cholesterol from 6.9±1.7 to 4.9±0.8 mmol/L and low- density lipoprotein (LDL) from 4.8±1.7 to 3.0±0.7 mmol/L (both P < 0.001), although total and LDL,cholesterol also decreased slightly in the placebo group. Vitamin E increased resting FBF from 2.1±0.3 to 2.4±0.3 mL/100 mL per min (P = 0.04) and decreased resting forearm vascular resistance from 42.1±4.2 to 36.1±3.4 units (P = 0.01), but the reduction in resting FBF with L -NMMA was not affected. Vasodilation in response to isotonic exercise, ACh and SNP was similar before and after treatment in the placebo, vitamin E, simvastatin and in the combined vitamin E,simvastatin groups. NG -Monomethyl- L -arginine infusion reduced resting FBF and functional hyperaemia in response to exercise and these responses were not altered by treatment. 5. These data suggest that while vitamin E therapy augments resting FBF and reduces forearm vascular resistance in young hypercholesterolaemic subjects, these effects may not be via NO-dependent pathways. Metabolic vasodilation and responses to the NO-mediated vasodilators ACh and SNP were not favourably affected by anti-oxidant or cholesterol-lowering therapy, either alone or in combination. [source] Real-time measurement of nitric oxide in single mature mouse skeletal muscle fibres during contractionsTHE JOURNAL OF PHYSIOLOGY, Issue 1 2007Deborah Pye Nitric oxide (NO) is thought to play multiple roles in skeletal muscle including regulation of some adaptations to contractile activity, but appropriate methods for the analysis of intracellular NO activity are lacking. In this study we have examined the intracellular generation of NO in isolated single mature mouse skeletal muscle fibres at rest and following a period of contractile activity. Muscle fibres were isolated from the flexor digitorum brevis muscle of mice and intracellular NO production was visualized in real-time using the fluorescent NO probe 4-amino-5-methylamino-2,,7,-difluorofluorescein diacetate (DAF-FM DA). Some leakage of DAF-FM was apparent from fibres loaded with the probe, but they retained sufficient probe to respond to changes in intracellular NO following addition of the NO donor 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)- N -methyl-1-propanamine (NOC-7) up to 30 min after loading. Electrically stimulated contractions in isolated fibres increased the rate of change in DAF-FM fluorescence by ,48% compared to non-stimulated fibres (P < 0.05) and the rate of change in DAF-FM fluorescence in the stimulated fibres returned to control values by 5 min after contractions. Treatment of isolated fibres with the NO synthase inhibitors NG -nitro- l -arginine methyl ester hydrochloride (l -NAME) or NG -monomethyl- l -arginine (l -NMMA) reduced the increase in DAF-FM fluorescence observed in response to contractions of untreated fibres. Treatment of fibres with the cell-permeable superoxide scavenger 4,5-dihydroxy-1,3-benzenedisulphonic acid (Tiron) also reduced the increase in fluorescence observed during contractions suggesting that superoxide, or more probably peroxynitrite, contributes to the fluorescence observed. Thus this technique can be used to examine NO generation in quiescent and contracting skeletal muscle fibres in real time, although peroxynitrite and other reactive nitrogen species may potentially contribute to the fluorescence values observed. [source] Effect of Nitric Oxide Synthase Inhibitors on Lipid Peroxide Formation in Liver Caused by Endotoxin ChallengeBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 4 2000Shuhei Sakaguchi This study investigated the effect of nitric oxide on lipid peroxide formation during endotoxaemia. Nitric oxide synthase inhibitors NG -monomethyl-L-arginine acetate (L-NMMA, 20 mg/kg, intravenously), NG -nitro-L-arginine-methyl ester (L-NAME, 10 mg/kg, intravenously), and NG -nitro-L-arginine (L-NA, 10 mg/kg, intravenously), and a relatively selective inducible nitric oxide synthase inhibitor aminoguanidine (10 mg/kg, intravenously), did not protect against endotoxin-induced death of mice. Superoxide dismutase activity in liver 18 hr after administration of endotoxin (6 mg/kg, intraperitoneally) to L-arginine analogues (L-NMMA, L-NAME, L-NA)-treated mice was lower than in mice treated with endotoxin alone, whereas the administration of L-arginine analogues increased xanthine oxidase activity in the livers of endotoxin-injected mice compared with mice treated with endotoxin alone. In mice treated with L-arginine analogues and aminoguanidine, the levels of non-protein sulfhydryl and lipid peroxide in liver 18 hr after endotoxin injection did not show significant differences from mice treated with endotoxin alone. L-Arginine analogues and aminoguanidine had little effect on lipid peroxide formation in liver caused by endotoxin. Treatment with aminoguanidine (300 ,M) significantly inhibited endotoxin-induced intracellular peroxide in J774A.1 cells, however, aminoguanidine did not affect endotoxin-induced cytotoxicity in J774A.1 cells. Our results clearly demonstrate that treatment with catalase (10 ,g/ml), D-mannitol (10 mM), or superoxide dismutase (100 U/ml), has little or no effect on nitric oxide production by endotoxin (1 ,g/ml)-activated J774A.1 cells. These findings suggest that nitric oxide is not crucial for lipid peroxide formation during endotoxaemia. Therefore, it is unlikely that nitric oxide plays a significant role in liver injury caused by free radical generation in endotoxaemia. [source] | |||||||||||||