nitroarginine and Chronic-Disease

Augmented vasoconstrictor reactivity is thought to play an important role in the development of chronic hypoxia (CH)-induced neonatal pulmonary hypertension. However, whether this response to CH results from pulmonary endothelial dysfunction and reduced nitric oxide (NO)-mediated vasodilation is not well understood. We hypothesized that neonatal CH enhances basal tone and pulmonary vasoconstrictor sensitivity by limiting NO-dependent pulmonary vasodilation. To test this hypothesis, we assessed the effects of the NO synthase (NOS) inhibitor

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Animals, Newborn; Chronic Disease; Enzyme Inhibitors; Free Radical Scavengers; Hypoxia; Lung; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Tyrosine; Vascular Resistance; Vasoconstriction; Vasoconstrictor Agents; Vasodilation

Studies on chronic inhibition of nitric oxide synthase (NOS) in the CNS suggest a plastic change in nitric oxide (NO) synthesis in areas related to motor control, which might protect the animal from the functional and behavioral consequences of NO deficiency. In the present study, the acute and chronic effect of the substrate analogue inhibitor N(G)-nitro-l-arginine (l-NNA) was examined on NO production, NO-sensitive cyclic guanosine monophosphate (cGMP) levels and the expression of NOS isoforms in the developing rat cerebellum. Acute intraperitoneal administration of the inhibitor (5-200mg/kg) to 21-day-old rats reduced NOS activity and NO concentration dose dependently by 70-90% and the tissue cGMP level by 60-80%. By contrast, chronic application of l-NNA between postnatal days 4-21 diminished the total NOS activity and NO concentration only by 30%, and the tissue cGMP level by 10-50%. Chronic treatment of 10mg/kg l-NNA induced neuronal (n)NOS expression in granule cells, as revealed by in situ hybridization, NADPH-diaphorase histochemistry and Western-blot, but it had no significant influence on tissue cGMP level or on layer formation of the cerebellum. However, a higher concentration (50mg/kg) of l-NNA decreased the intensity of the NADPH-diaphorase reaction in granule cells, significantly reduced cGMP production, and retarded layer formation and induced inducible (i)NOS expression & activity in glial cells. Treatments did not affect endothelial (e)NOS expression. The administration of the biologically inactive isomer D-NNA (50mg/kg) or saline was ineffective. The present findings suggest the existence of a concentration-dependent compensatory mechanism against experimentally-induced cronich inhibition of NOS, including nNOS or iNOS up-regulation, which might maintain a steady-state NO level in the developing cerebellum.

Topics: Animals; Cerebellum; Chronic Disease; Drug Administration Schedule; Gene Expression Regulation, Enzymologic; Homeostasis; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitroarginine; Rats; Rats, Wistar

The effects of chronic hypoxia (CH) on respiratory muscle are poorly understood. The aim of the present study was to examine the effects of CH on respiratory muscle structure and function, and to determine whether nitric oxide is implicated in respiratory muscle adaptation to CH. Male Wistar rats were exposed to CH for 1-6 weeks. Sternohyoid and diaphragm muscle contractile properties, muscle fibre type and size, the density of fibres expressing sarco/endoplasmic reticulum calcium-ATPase (SERCA) 2 and sodium-potassium ATPase (Na+,K+-ATPase) pump content were determined. Muscle succinate dehydrogenase (SDH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase activities were also assessed. Acute and chronic blockade of nitric oxide synthase (NOS) was employed to determine whether or not NO is critically involved in functional remodelling in CH muscles. CH improved diaphragm, but not sternohyoid, fatigue tolerance in a time-dependent fashion. This adaptation was not attributable to increased SDH or NADPH dehydrogenase activities. The areal density of muscle fibres and relative area of fibres expressing SERCA2 were unchanged. Na+,K+-ATPase pump content was significantly increased in CH diaphragm. Chronic NOS inhibition decreased diaphragm Na+,K+-ATPase pump content and prevented CH-induced increase in muscle endurance. This study provides novel insight into the mechanisms involved in CH-induced muscle plasticity. The results may be of relevance to respiratory disorders characterised by CH, such as chronic obstructive pulmonary disease.

Topics: Adaptation, Physiological; Animals; Chronic Disease; Diaphragm; Enzyme Inhibitors; Hypoxia; Male; Muscle Fatigue; Muscle, Skeletal; NADPH Dehydrogenase; Nitric Oxide Synthase; Nitroarginine; Physical Endurance; Rats; Rats, Wistar; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Sodium-Potassium-Exchanging ATPase; Succinate Dehydrogenase

The aims of this study were: 1) to obtain an experimental model reproducing the characteristics of chronicity and spontaneous relapses found in inflammatory bowel disease (IBD) and 2) to correlate these changes with intestinal motility and bacteria translocation. For this purpose, two groups of Sprague-Dawley rats were used: a treated group that received two subcutaneous injections of indomethacin (7.5 mg/kg) 48 h apart and a control group that received saline. Blood leukocytes, TNF, and fecal parameters were monitored for 90 days after treatment. In treated rats, a cyclic oscillation of blood leukocytes and TNF concomitant with an inverse correlation of fecal output was observed. Treated rats were then selected either during their highest or lowest blood leukocyte values for motor activity and microbiological evaluation. Controls were obtained in age-matched rats. Rats with high leukocyte levels showed a decrease of motor activity. In contrast, animals with low leukocyte levels presented hypermotility. Bacterial overgrowth accompanied by bacterial translocation was found in the group with high leukocytes, whereas no differences were observed between the control and indomethacin groups during the lowest leukocyte phase. We obtained a model of IBD characterized by a chronic cyclic oscillation of intestinal motility, flora, and inflammatory blood parameters. During the high-leukocyte stage, motor activity decrease is related to bacterial translocation. This phase is followed by a reactive one characterized by hypermotility associated with a decrease in both bacterial growth and leukocytes. However, as in IBD, this reaction seems unable to prevent a return to relapse.

Topics: Acute Disease; Animals; Anti-Inflammatory Agents, Non-Steroidal; Bacteria; Bacterial Infections; Bacterial Translocation; Cholecystokinin; Chronic Disease; Enteritis; Enzyme Inhibitors; Gastrointestinal Motility; Indomethacin; Injections, Subcutaneous; Intestinal Diseases; Leukocyte Count; Male; Nitroarginine; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha

PKC augments calcium sensitivity in spontaneously hypertensive rats and contributes to alpha(2)-adrenergic receptor (AR) contraction in rabbit saphenous vein. We showed previously that denuded aortic rings from N(omega)-nitro-l-arginine-treated hypertensive rats (LHR) contract more to CaCl(2) and to the alpha(2)-AR agonist UK-14304 than do rings from normotensive rats (NR). We hypothesized that enhanced PKC activity or a change in PKC isoform contributes to augmented calcium sensitivity and enhanced alpha(2)-AR contraction in LHR aorta. Current studies demonstrate that non-isoform-specific PKC inhibitors reduced UK-14304 contraction in both NR and LHR aorta. However, the calcium-dependent PKC inhibitor Gö-6976 only attenuated contraction in LHR aorta. Additionally, UK-14304 translocated PKC-delta to the membrane in NR aorta, whereas PKC-alpha was translocated to the membrane in LHR aorta. Finally, in ionomycin-permeabilized aorta Gö-6976 eliminated enhanced basal and augmented alpha(2)-AR-stimulated calcium sensitivity in LHR aorta but did not affect NR contraction. Together, these data suggest that PKC-alpha contributes to augmented calcium sensitivity and alpha(2)-AR reactivity after chronic nitric oxide synthase inhibition hypertension.

Topics: Animals; Aorta; Calcium; Chronic Disease; Hypertension; In Vitro Techniques; Male; Nitric Oxide Synthase; Nitroarginine; Protein Kinase C; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha-2; Vasoconstriction; Vasomotor System

We tested the hypotheses that pregnancy increases the uterine artery (UA) vasodilator response to flow and that this increase is impaired under conditions of chronic hypoxia (30 days, simulated elevation 3,960 m). UA were isolated from 24 normoxic or chronically hypoxic midpregnant guinea pigs and studied with the use of pressure myography. Normoxic pregnancy increased UA flow vasodilator response and protected against a rise in wall shear stress (WSS). Chronic hypoxia opposed these effects, prompting vasoconstriction at high flow and increasing WSS above levels seen in normoxic pregnant UA. The nitric oxide synthase inhibitor N(G)-nitro-l-arginine (l-NNA) eliminated the pregnancy-associated increase in flow vasodilation in normoxic UA, suggesting that increased nitric oxide production was responsible. The considerable residual vasodilation after nitric oxide synthase and cyclooxygenase inhibition implicated endothelial-derived hyperpolarizing factor (EDHF) as an additional contributor to flow vasodilation. l-NNA increased flow vasodilation in UA from chronically hypoxic animals, suggesting that chronic hypoxia may have lowered EDHF or elevated peroxynitrite production. In conclusion, flow is an important physiological vasodilator for the acute and more chronic UA dimensional changes required to increase uteroplacental blood flow during normal pregnancy. Chronic hypoxia may be a mechanism that opposes the pregnancy-associated rise in UA flow vasodilation, thereby increasing the incidence of preeclampsia and intrauterine growth restriction at a high altitude.

Topics: Altitude; Animals; Arteries; Atmosphere Exposure Chambers; Blood Flow Velocity; Chronic Disease; Enzyme Inhibitors; Female; Guinea Pigs; Hypoxia; In Vitro Techniques; Meclofenamic Acid; Nitric Oxide Synthase; Nitroarginine; Pregnancy; Stress, Mechanical; Uterus; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

We hypothesized that altered vasoreactivity in perinatal pulmonary hypertension (PH) is characterized by abnormal responses to hemodynamic stress, including the loss of flow-induced vasodilation and an augmented myogenic response. Therefore, we studied the acute hemodynamic effects of brief compression of the ductus arteriosus (DA) in control fetal lambs and in lambs during exposure to chronic PH. In both groups, acute DA compression decreased pulmonary vascular resistance (PVR) by 20% at baseline (day 0). After 2 days of hypertension, acute DA compression paradoxically increased PVR by 50% in PH lambs, whereas PVR decreased by 25% in controls. During the 8-day study period, PVR increased during acute DA compression in PH lambs, whereas acute DA compression continued to cause vasodilation in controls. Brief treatment with the nitric oxide (NO) synthase inhibitor nitro-L-arginine (L-NA) increased basal PVR in control but not PH lambs, suggesting decreased NO production in PH lambs. Chronic hypertension increased the myogenic response after L-NA in PH lambs, whereas the myogenic response remained unchanged in controls. The myogenic response was inhibited by nifedipine in PH lambs, suggesting that the myogenic response is dependent upon the influx of extracellular calcium. We conclude that chronic PH impairs flow-induced vasodilation and increases the myogenic response in fetal lung. We speculate that decreased NO signaling and an augmented myogenic response contributes to abnormal vasoreactivity in PH.

Topics: Animals; Calcium Channel Blockers; Calcium Channels; Chronic Disease; Ductus Arteriosus; Enzyme Inhibitors; Hypertension; Lung; Muscle, Smooth, Vascular; Nifedipine; Nitric Oxide Synthase; Nitroarginine; Pressure; Pulmonary Circulation; Reference Values; Sheep; Time Factors; Vasodilation; Vasomotor System

Chronic hypoxia (CH) augments endothelium-derived nitric oxide (NO)-dependent pulmonary vasodilation; however, responses to exogenous NO are reduced following CH in female rats. We hypothesized that CH-induced attenuation of NO-dependent pulmonary vasodilation is mediated by downregulation of vascular smooth muscle (VSM) soluble guanylyl cyclase (sGC) expression and/or activity, increased cGMP degradation by phosphodiesterase type 5 (PDE5), or decreased VSM sensitivity to cGMP. Experiments demonstrated attenuated vasodilatory responsiveness to the NO donors S-nitroso-N-acetylpenicillamine and spermine NONOate and to arterial boluses of dissolved NO solutions in isolated, saline-perfused lungs from CH vs. normoxic female rats. In additional experiments, the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, blocked vasodilation to NO donors in lungs from each group. However, CH was not associated with decreased pulmonary sGC expression or activity as assessed by Western blotting and cGMP radioimmunoassay, respectively. Consistent with our hypothesis, the selective PDE5 inhibitors dipyridamole and T-1032 augmented NO-dependent reactivity in lungs from CH rats, while having little effect in lungs from normoxic rats. However, the attenuated vasodilatory response to NO in CH lungs persisted after PDE5 inhibition. Furthermore, CH similarly inhibited vasodilatory responses to 8-bromoguanosine 3'5'-cyclic monophosphate. We conclude that attenuated NO-dependent pulmonary vasodilation after CH is not likely mediated by decreased sGC expression, but rather by increased cGMP degradation by PDE5 and decreased pulmonary VSM reactivity to cGMP.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blotting, Western; Chronic Disease; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Enzyme Inhibitors; Female; Guanylate Cyclase; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Polycythemia; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Vasodilation

Female rats develop less severe pulmonary hypertension (PH) in response to chronic hypoxia compared with males, thus implicating a potential role for ovarian hormones in mediating this gender difference. Considering that estrogen upregulates endothelial nitric oxide (NO) synthase (eNOS) in systemic vascular tissue, we hypothesized that estrogen inhibits hypoxic PH by increasing eNOS expression and activity. To test this hypothesis, we examined responses to the endothelium-derived NO-dependent dilator ionomycin and the NO donors S-nitroso-N-acetylpenicillamine and spermine NONOate in U-46619-constricted, isolated, saline-perfused lungs from the following groups: 1) normoxic rats with intact ovaries, 2) chronic hypoxic (CH) rats with intact ovaries, 3) CH ovariectomized rats given 17 beta-estradiol (E(2)beta), and 4) CH ovariectomized rats given vehicle. Additional experiments assessed pulmonary eNOS levels in each group by Western blotting. Our findings indicate that E(2)beta attenuated chronic hypoxia-induced right ventricular hypertrophy, pulmonary arterial remodeling, and polycythemia. Furthermore, although CH augmented vasodilatory responsiveness to ionomycin and increased pulmonary eNOS expression, these responses were not potentiated by E(2)beta. Finally, responses to S-nitroso-N-acetylpenicillamine and spermine NONOate were similarly attenuated in all CH groups compared with normoxic control groups. We conclude that the inhibitory influence of E(2)beta on chronic hypoxia-induced PH is not associated with increased eNOS expression or activity.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Chronic Disease; Endothelium, Vascular; Enzyme Inhibitors; Estradiol; Female; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Ionomycin; Ionophores; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Nitrogen Oxides; Ovariectomy; Penicillamine; Polycythemia; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Spermine; Vascular Resistance; Vasoconstrictor Agents; Vasodilation

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

Previous studies suggest that inducible (i) nitric oxide synthase (NOS) expression within the pulmonary vasculature is increased in rats with chronic hypoxia (CH)-induced pulmonary hypertension. We therefore hypothesized that enhanced iNOS expression associated with CH causes attenuated pulmonary vasoconstrictor responsiveness. To test this hypothesis, we examined the effect of selective iNOS blockade with L-N6-(1-iminoethyl)lysine dihydrochloride (L-NIL) and nonselective NOS inhibition with Nomega-nitro-L-arginine (L-NNA) on vasoconstrictor responses to U-46619 in isolated saline-perfused lungs from both control and CH (4 wk at 380 mmHg) rats. We additionally measured pulmonary hemodynamic responses to L-NIL in conscious CH rats (fraction of inspired O2 = 0.12). Finally, iNOS mRNA levels were assessed in lungs from each group of rats using ribonuclease protection assays. Despite a significant increase in iNOS mRNA expression after exposure to CH, responses to U-46619 were unaltered by L-NIL but augmented by L-NNA in lungs from both control and CH rats. Pulmonary hemodynamics were similarly unaltered by L-NIL in conscious CH rats. We conclude that iNOS does not modulate pulmonary vasoconstrictor responsiveness after long-term hypoxic exposure.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Chronic Disease; Enzyme Inhibitors; Hemodynamics; Hypoxia; In Vitro Techniques; Lipopolysaccharides; Lung; Lysine; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Vascular Resistance; Vasoconstriction; Vasoconstrictor Agents

We performed experiments to test the hypothesis that experimental heart failure (HF) is associated with altered nitric oxide (NO)-dependent influences on the renal microvasculature, including diminished modulation of constrictor responses to ANG II. Eight to ten weeks after inducing HF in rats by coronary artery ligation, we administered enalaprilat to suppress ANG II synthesis and studied renal arteriolar function using the in vitro blood-perfused juxtamedullary nephron technique. In kidneys from sham-operated rats, NO synthase inhibition [100 microM Nomega-nitro-L-arginine (L-NNA)] reduced afferent arteriolar diameter by 4.1 +/- 0.6 microm and enhanced ANG II responsiveness (10 nM ANG II decreased afferent diameter by 10.1 +/- 1.4 micrometer before and 12.8 +/- 1.6 micrometer during L-NNA treatment; P < 0.05). In kidneys from HF rats, L-NNA did not alter afferent arteriolar baseline diameter or ANG II responsiveness (10 nM ANG II decreased diameter by 12.5 +/- 1.5 micrometer before and 12.5 +/- 2.3 micrometer during L-NNA). The effects of L-NNA on efferent arteriolar function were also abated in HF rats. In renal cortex of HF rats, NO synthase activity was decreased by 63% and superoxide dismutase activity was diminished by 39% relative to tissue from sham-operated rats. Urinary nitrate/nitrite excretion was also reduced in HF rats. Thus both diminished synthesis and augmented degradation are likely to contribute to a decreased renal microvascular impact of endogenous NO during chronic HF, the consequences of which include loss of NO-dependent modulation of ANG II-induced vasoconstriction.

Topics: Animals; Arterioles; Cardiac Output, Low; Chronic Disease; Enzyme Inhibitors; Kidney; Male; Microcirculation; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Renal Circulation; Superoxide Dismutase

In lungs from chronically hypoxic (CH, 3 weeks at 10% inspired O2) rats, oxygenation (20% O2, 5% CO2, 75% N2; PO2 121 mmHg) of the perfusate increases pulmonary perfusion pressure (PPP) and lung weight (LW). Hypoxic perfusate (95% N2, 5% CO2; PO2 5.5 mmHg) had no effect on PPP in lungs from CH rats. Indomethacin and nitro-L-arginine (L-NOARG) augmented the oxygen-induced increase in PPP. In contrast, the free radical scavengers superoxide dismutase (SOD) plus catalase delayed the onset of oxygen-induced vasoconstriction, while the endothelin (ET)B receptor antagonist BQ788 inhibited it. The ET(A) receptor antagonist BQ123 did not affect the PPP changes. This suggests a role for endogenous endothelins and ET(B) receptors in mediating the oxygenation-induced pulmonary vasoconstriction. Indomethacin had no effect on oxygen-induced lung weight (LW) changes while BQ788 and L-NOARG reduced the LW increase. This evidence shows that ET(B) receptor activation and NO generation are involved in the LW changes. In conclusion, oxygenation of the perfusate in isolated lungs from CH rats leads to pulmonary vasoconstriction which involves endothelins and activation of ET(B) receptors. In addition, increased NO production associated with ET(B) receptor activation is the prime stimulus for observed LW increase.

Topics: Adrenergic alpha-Antagonists; Animals; Chronic Disease; Cyclooxygenase Inhibitors; Endothelin Receptor Antagonists; Endothelins; Free Radical Scavengers; Hypoxia; In Vitro Techniques; Indomethacin; Lung; Male; Nitroarginine; Oxygen; Perfusion; Pressure; Pulmonary Artery; Rats; Rats, Wistar; Vasoconstriction

Protease-activated receptor-2 (PAR-2) can be activated after proteolysis of the amino terminal of the receptor by trypsin or by synthetic peptides with a sequence corresponding to the endogenous tethered ligand exposed by trypsin (eg, SLIGRL-NH(2)). PAR-2 mediates nitric oxide (NO)-dependent dilatation in cerebral arteries, but it is unknown whether PAR-2 function is altered in cardiovascular diseases. Since hypertension selectively impairs NO-mediated cerebral vasodilatation in response to acetylcholine and bradykinin, we sought to determine whether PAR-2-mediated vasodilatation is similarly adversely affected by this disease state.. We studied basilar artery responses in Wistar-Kyoto rats (WKY) (normotensive) and spontaneously hypertensive rats (SHR) in vivo (cranial window preparation) and in vitro (isolated arterial rings). The vasodilator effects of acetylcholine, sodium nitroprusside, and activators of PAR-2 and protease-activated receptor-1 (PAR-1) were compared in WKY versus SHR. Immunohistochemical localization of PAR-2 was also assessed in the basilar artery.. Increases in basilar artery diameter in response to acetylcholine were 65% to 85% smaller in SHR versus WKY, whereas responses to sodium nitroprusside were not different. In contrast to acetylcholine, vasodilatation in vivo to SLIGRL-NH(2) was largely preserved in SHR, and SLIGRL-NH(2) was approximately 3-fold more potent in causing vasorelaxation in SHR versus WKY in vitro. In both strains, responses to SLIGRL-NH(2) were abolished by N(G)-nitro-L-arginine, an inhibitor of NO synthesis. Activators of PAR-1 had little or no effect on the rat basilar artery. PAR-2-like immunoreactivity was observed in both the endothelial and smooth muscle cells of the basilar artery in both strains of rat.. These data indicate that NO-mediated vasodilatation to PAR-2 activation is selectively preserved or augmented in SHR and may suggest protective roles for PAR-2 in the cerebral circulation during chronic hypertension.

Topics: Acetylcholine; Animals; Cerebral Arteries; Chronic Disease; Enzyme Inhibitors; Hypertension; Male; Nitroarginine; Nitroprusside; Oligopeptides; Peptide Fragments; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, PAR-1; Receptor, PAR-2; Receptors, Thrombin; Vasodilation

In order to investigate whether selective hypertriglyceridemia impairs endothelium-dependent vasodilatation in the rat hindlimb, rats were selectively bred to establish two strains, one with a pronounced hypertriglyceridemia (HT) and the other with normal plasma levels of triglycerides (LT).. Carotid arteries and aortae removed from 3, 6, 9 and 12 month old LT- and HT-rats exhibited a normal morphology. However, marked morphological differences were observed between vessels from 18-20 month old HT- and LT-rats. The endothelium-dependent vasodilator acetylcholine (2 to 50 micrograms/kg), administered into the iliac artery, elicited a concentration-dependent increase in hindlimb blood flow which was not different in 3, 6 and 9 month old LT- or HT-rats but was impaired in 12 and 18-20 month old HT-rats. In contrast the endothelium-independent vasodilator sodium nitroprusside enhanced blood flow in both strains to a similar extent. Neither administration of the nitric oxide (NO) synthase (NOS) substrate, L-arginine, nor the NOS inhibitor NGnitro-L-arginine, affected the responsiveness to endothelium-dependent vasodilators in 12 month old HT-rats. These attenuated responses could not be attributed to a decrease in endothelial NOS expression as Western blot analysis revealed identical levels of this enzyme in the aortae and carotid arteries from LT- and HT-rats. Determination of superoxide anion (O2-) formation however, demonstrated a markedly elevated production of O2- in aortae from HT-rats.. We conclude that chronic selective hypertriglyceridemia, an independent risk factor in the development and progression of atherosclerosis, leads to an endothelial dysfunction which is associated with an increased vascular O2- production and a subsequent decrease in bioavailable NO.

Topics: Acetylcholine; Animals; Aorta; Arginine; Blotting, Western; Carotid Arteries; Chronic Disease; Endothelium, Vascular; Hindlimb; Hypertriglyceridemia; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Superoxides; Vasodilation

1. The effect of chronic ischaemic myocardial remodelling on small coronary artery reactivity in vitro was studied in a newly developed pig model. 2. Pigs were subjected to selective intracoronary embolizations with microspheres in the left anterior descending artery and circumflex artery causing scattered myocardial fibrosis. After an observation period of 130 days, heart dimensions and ejection fraction were determined with magnetic resonance imaging. Small arteries were isolated from the left ventricle and mounted as ring preparations in a myograph. Control arteries were taken from matched non-embolized pigs. 3. Compared with control pigs, end-systolic and diastolic volumes increased and left ventricular mass nearly doubled in embolized pigs. This indicates substantial myocardial hypertrophy, as the fraction area of fibrosis was only 12%. 4. Coronary small arteries preconstricted with 30 mmol/l KCI showed a normal contractile response to acetylcholine and 5-hydroxytryptamine. Sensitivity of the relaxation to bradykinin was nearly 3-fold increased and also slightly enhanced to isoprenaline in arteries from embolized pigs compared with controls, whereas relaxation to 5-hydroxytryptamine in the presence of ketanserin was similar. After inhibition of nitric oxide synthase with NG-nitro-L-arginine the sensitivity to acetylcholine increased to a similar extent in arteries from embolized pigs and controls. NG-Nitro-L-arginine abolished the relaxing effects of bradykinin and of 5-hydroxytryptamine in the presence of ketanserin. 5. We conclude that both the contractile function of the smooth muscle cells and the endothelial production or action of nitric oxide is preserved or slightly enhanced in coronary small arteries from pigs with chronic myocardial remodelling.

Topics: Acetylcholine; Animals; Bradykinin; Cardiomegaly; Cardiotonic Agents; Chronic Disease; Coronary Vessels; Drug Synergism; Endothelium, Vascular; Isoproterenol; Ketanserin; Models, Biological; Myocardial Ischemia; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Serotonin; Serotonin Antagonists; Swine; Vasoconstrictor Agents

The present study aimed to examine the effects of N omega-nitro-L-arginine (LNA) on the early ischemic neuronal damage (EIND). All the experiments were carried out under general anesthesia, maintaining the blood gases and the body temperature within the physiological ranges. The local CBF, the topographically corresponding cortical specific gravity, and the volume of EIND were determined in each rat, which was subjected to prolonged or temporary occlusion of middle cerebral artery (MCA) using our original miniclip. Significant cortical edema developed only in the brain area where the local CBF value was below 200 ml 100 g-1 min-1. The prolonged MCA occlusion for 1, 2, and 4 h induced a time-dependent increase in the severity of cortical edema and the volume of EIND. Removal of the clip invariably induced recirculation. Compared to that induced by 4 h prolonged ischemia, the brain damage was improved by 1 h MCA occlusion followed by 3 h recirculation, whereas it was significantly worsened by 2 h ischemia followed by 2 h recirculation. While LNA [1 mg, i.p., given two times during the experiment] only partially inhibited the activity of brain nitric oxide synthase, it remarkably ameliorated EIND of both prolonged ischemia and recirculation in this model. The above findings indicate the pathogenic role of nitric oxide in prolonged ischemia as well as recirculation.

Topics: Animals; Blood Pressure; Brain Ischemia; Cerebral Cortex; Chronic Disease; Enzyme Inhibitors; Neurons; Nitric Oxide Synthase; Nitroarginine; Rats; Reperfusion Injury; Specific Gravity; Time Factors

Neuroglycopenia induced by administration of 2-deoxy-D-glucose is known to stimulate the secretion of both insulin and glucagon in mice by a mechanism that is dependent on neural activity. In the present study, we examined whether the neurotransmitter nitric oxide (NO) is involved in this process. Therefore, 2-deoxy-D-glucose (500 mg/kg) was injected intravenously alone or together with the inhibitor of NO synthase, NG-nitro-L-arginine methyl ester (50 mg/kg) to conscious mice. It was found that NG-nitro-L-arginine methyl ester inhibited the increased plasma levels of both insulin (by 26%; P = 0.039) and glucagon (by 45%; P < 0.001) at 10 min after injection of 2-deoxy-D-glucose. Similarly, the NO synthase inhibitor, NG-nitro-L-arginine, which is devoid of the anticholinergic property of NG-nitro-L-arginine methyl ester, inhibited the responses of both insulin (by 53%; P = 0.026) and glucagon (by 57%; P = 0.003) to 2-deoxy-D-glucose. In contrast, the stereoisomer of NG-nitro-L-arginine methyl ester, NG-nitro-D-arginine methyl ester, which is devoid of NO synthase inhibitory activity, was without effect on 2-deoxy-D-glucose-induced insulin and glucagon secretion. Plasma levels of adrenaline and noradrenaline after administration of 2-deoxy-D-glucose were also reduced by NG-nitro-L-arginine methyl ester. In contrast, the insulin and glucagon secretory responses to intravenous injection of arginine (250 mg/kg), glucose (500 mg/kg) or the cholinergic agonist, carbachol (30 micrograms/kg), were not influenced by NG-nitro-L-arginine methyl ester, NG-nitro-D-arginine methyl ester or NG-nitro-L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Glucose; Carbachol; Catecholamines; Chronic Disease; Deoxyglucose; Drug Interactions; Female; Hypoglycemia; Insulin; Insulin Secretion; Islets of Langerhans; Mice; Mice, Inbred Strains; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Stimulation, Chemical

To define the role of endothelium-derived relaxing factor (EDRF) in the regulation of renal hemodynamics in the hydronephrotic kidney.. Experiments were performed in control rats and in rats that had undergone unilateral ureteral ligation 6 weeks before. Renal blood flow was monitored before and after inhibition of EDRF synthesis in the control and hydronephrotic animals. Videomicroscopy was also performed in hydronephrotic animals to observe directly the effect of inhibition of EDRF synthesis on the renal microcirculation.. Inhibition of EDRF synthesis resulted in a 61% decrease in renal blood flow in the control animals compared with only a 27% decrease for the hydronephrotic animals. The videomicroscopy studies demonstrated that inhibition of EDRF synthesis results in significant vasoconstriction of the preglomerular and postglomerular resistance vessels.. Although EDRF continues to play a significant role in the maintenance of renal blood flow in the chronically obstructed kidney, EDRF synthesis by the renal vascular endothelium may be reduced in this setting, contributing to ischemic renal atrophy.

Topics: Acetylcholine; Animals; Arginine; Chronic Disease; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Hemodynamics; Hydronephrosis; Male; Microcirculation; Microscopy, Video; Nitric Oxide; Nitroarginine; Rats; Rats, Wistar; Renal Circulation; Vasoconstriction

This study was designed to determine the efficacy of L-arginine in healing of gastric ulcers induced by acetic acid and to assess the role of nitric oxide (NO), prostaglandins, gastrin and polyamines in the healing process. Intragastric administration of L-arginine (32.5-300 mg/kg/day) enhanced the healing rate of these ulcers in a dose-dependent manner, while D-arginine (300 mg/kg/day) was not effective. The acceleration of healing by L-arginine was accompanied by a marked increase in gastric blood flow (GBF) at the ulcer margin, and an enhancement of serum gastrin level, mucosal DNA synthesis, and DNA and RNA contents and angiogenesis in the granulation tissue in the ulcer bed. A similar increase in ulcer healing associated with hyperemia at the ulcer margin and enhanced angiogenesis but without alteration in serum gastrin were observed after treatment with glyceryl trinitrate, an NO exogenous supplier. Treatment with NG-nitro-L-arginine (L-NNA), an inhibitor of NO synthase, delayed ulcer healing and this was accompanied by a reduction of GBF at the ulcer margin and in angiogenesis in granulation tissue and by a decrease in serum gastrin level and mucosal growth. Addition of L-arginine to L-NNA restored ulcer healing, hyperemia at the ulcer margin and angiogenesis and prevented the fall in serum gastrin and mucosal growth caused by L-NNA. Pretreatment with indomethacin also delayed ulcer healing and this was reversed by the coadministration of L-arginine. Inhibition of polyamine biosynthesis by difluoro-methyl-ornithine completely abolished the acceleration of the healing and the increase in mucosal growth induced by L-arginine. Our findings indicate that L-arginine accelerates ulcer healing due to its hyperemic, angiogenic and growth-promoting actions, possibly involving NO, gastrin and polyamines.

Topics: Animals; Arginine; Chronic Disease; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Eflornithine; Gastrins; Indomethacin; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroglycerin; Polyamines; Prostaglandins; Rats; Rats, Wistar; Regional Blood Flow; Stomach; Stomach Ulcer; Vasodilator Agents

We have previously demonstrated that arginine vasopressin (AVP) dilates the preconstricted pulmonary vasculature via the release of nitric oxide (NO). However, recent evidence suggests that NO release in response to other agents may be suppressed in lungs from animals that have been chronically exposed to hypoxia. The purpose of the present experiment was to determine whether vasopressinergic pulmonary vasodilation is similarly affected by chronic exposure to hypoxia (barometric pressure = 380 Torr for 4 wk). Inhibition of NO synthesis with N omega-nitro-L-arginine (L-NNA) had no effect on baseline perfusion pressure in isolated salt-perfused lungs from either control or chronically hypoxic rats. Similarly, pulmonary vasodilatory responses to AVP and the calcium ionophore A23187 were unaffected by chronic hypoxic exposure. Pretreatment with the cyclooxygenase inhibitor meclofenamate did not alter vasopressinergic pulmonary vasodilation in lungs from either control or chronically hypoxic animals, ruling out involvement of vasodilator prostaglandins in the response to AVP. In contrast, vasodilatory responses to both AVP and A23187 were inhibited by L-NNA pretreatment not only in lungs from control animals but also in lungs from chronically hypoxic rats, suggesting the involvement of NO in the vasodilatory response. The inhibition by L-NNA was reversible by prior addition of excess L-arginine but not by D-arginine. In addition, vasodilatory responses to the endothelium-independent vasodilators sodium nitroprusside and isoproterenol were unaffected by chronic hypoxic exposure. We conclude that endothelium-dependent vasodilation remains intact in male Sprague-Dawley rats after chronic hypoxic exposure.

Topics: Air Pressure; Animals; Arginine; Arginine Vasopressin; Calcimycin; Chronic Disease; Endothelium, Vascular; Hypoxia; In Vitro Techniques; Isoproterenol; Male; Meclofenamic Acid; Nitroarginine; Nitroprusside; Prostaglandins; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Vasodilation; Vasodilator Agents

The role of endogenous endothelium-derived relaxing factor (EDRF) in splanchnic blood flow was assessed in normal and portal vein-stenosed rats (PSRs). Specific and maximal inhibition of EDRF was achieved by intravenous administration of NG-nitro-L-arginine (L-NOARG) as a 1.75 mumol/kg bolus, followed by constant infusion of 1.75 mumol/kg for 20 min. Pretreatment with L-arginine (175 mumol/kg iv) completely blocked both hypertension and the reduction in blood flow induced by L-NOARG. Pretreatment with D-arginine (175 mumol/kg iv) and prazosin (500 micrograms/kg iv) did not attenuate the pressor effect of L-NOARG. These results indicate that L-NOARG selectively blocks EDRF. The blood flow to the stomach, duodenum, jejunum, ileum, cecum, and colon in control rats was 81.1 +/- 8.7, 199.1 +/- 21.9, 153.3 +/- 20.0, 68.6 +/- 10.6, 79.4 +/- 11.8, and 59.3 +/- 7.8 ml.min-1.100 g-1, respectively, and in PSRs was 141.4 +/- 10.8, 244.0 +/- 10.4, 208.3 +/- 9.8, 126.8 +/- 13.0, 166.9 +/- 16.5, and 94.8 +/- 4.7 ml.min-1.100 g-1, respectively. Blood flow was measured using the radioactive microsphere method. L-NOARG significantly reduced blood flow to the stomach, duodenum, jejunum, ileum, cecum, and colon in control rats by 47, 44, 48, 55, 40, and 41%, respectively, and in PSRs by 30, 27, 36, 33, 28, and 23%, respectively. The magnitude of blood flow reduction in PSRs was lower than in normal rats. These results indicate that EDRF plays an important role in control of the splanchnic circulation, but its effect on the hyperdynamic circulation observed in PSRs is insignificant.

Topics: Animals; Arginine; Chronic Disease; Hypertension, Portal; Male; Nitric Oxide; Nitroarginine; Rats; Rats, Inbred Strains; Reference Values; Regional Blood Flow; Renal Circulation; Splanchnic Circulation; Testis