nitroarginine and Necrosis

It is known that ouabain, a selective inhibitor of Na/K-ATPase, not only can cause the activation of signal cascades, which regulate the cell viability, but also can cause the accumulation of free radicals, which can evoke the oxidative stress. We have shown that the nanomolar concentrations of ouabain result in the temporary increase in the level of intracellular free radicals, but the millimolar concentration of ouabain induces a stable intracellular accumulation of free radicals in rat thymocytes. The increasing level of free radicals resulting from both low and high concentrations of ouabain can be attenuated by the antioxidant, carnosine. Moreover, the long-term incubation with ouabain leads to the cell death by necrosis and apoptosis. Ouabain-mediated apoptosis and necrosis were also abolished by carnosine.

Topics: Animals; Apoptosis; Calcium Signaling; Carnosine; Culture Media; Dose-Response Relationship, Drug; Enzyme Activation; Free Radicals; Necrosis; Nitric Oxide Synthase; Nitroarginine; Ouabain; Protein Isoforms; Rats; Rats, Inbred WKY; Signal Transduction; Sodium-Potassium-Exchanging ATPase; Thymocytes

Cardiovascular dysfunction characterizes septic shock, inducing multiple organ failure and a high mortality rate. In the heart, it has been shown an up-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions with subsequent overproduction of nitric oxide (NO) and eicosanoids. This study is focused on the links between these products of inflammation and cell loss of mouse cardiomyocytes during treatment by the Salmonella typhimurium lipopolysaccharide (LPS) in presence or in absence of NOS or COX inhibitors. LPS induced RelA/NF-κB p65 activation, iNOS and COX-2 up-regulations, resulting in NO and prostacyclin releases. These effects were reversed by the NO-synthase inhibitor and increased by the specific COX-2 inhibitor. Immunostainings with FITC-conjugated anti-Annexin-V and propidium iodide and caspase 3/7 activity assay showed that cardiomyocyte necrosis was inhibited by L-NA during LPS treatment challenge, while apoptosis was induced in presence of both LPS and NS-398. No effect on LPS cellular injury was observed using the specific cyclooxygenase-1 (COX-1) inhibitor, SC-560. These findings strongly support the hypothesis of a link between iNOS-dependent NO overproduction and LPS-induced cell loss with a selective protective role allotted to COX-2 and deriving prostacyclins.

Topics: Animals; Apoptosis; Cells, Cultured; Cyclooxygenase 2; Cyclooxygenase Inhibitors; Drug Antagonism; Drug Therapy, Combination; Epoprostenol; Lipopolysaccharides; Mice; Mice, Inbred Strains; Myocytes, Cardiac; Necrosis; Nitric Oxide; Nitric Oxide Synthase Type II; Nitroarginine; Nitrobenzenes; Pyrazoles; Sulfonamides; Up-Regulation

We have previously reported that the hypoxic cytotoxin tirapazamine causes central vascular dysfunction in HCT-116 xenografts. Here we further extend this finding to SiHa xenografts and SCCVII murine tumors. Within 1 day after treatment with tirapazamine both tumor types develop areas of non-perfused tissue in central regions of tumors. To explore the mechanism by which the hypoxic cytotoxin tirapazamine causes vascular dysfunction we altered the blood oxygen content with carbogen (95% O(2) and 5% CO(2)) breathing in tumor bearing mice. Carbogen treatment was able to decrease the number of tumors responding to tirapazamine but was not able to eradicate the vascular dysfunction completely. In complementary in vitro studies, immunohistochemical staining of tirapazamine-treated endothelial cells indicated that, unlike the vascular targeting agent (VTA) combretastatin-A-4-phosphate, the vascular effects caused by tirapazamine are not due to microtubule disruption. Another possible mechanism of action for tirapazamine could involve its ability to inhibit nitric oxide synthase (NOS). Studies combining other vascular targeting agents (VTAs) such as the combretastatins have shown a potentiation of vascular disruption in tumors when combined with NOS inhibitors, possibly due to vessel constriction from decreased nitric oxide (NO) levels. We propose the theory that vascular dysfunction caused by tirapazamine may be via NOS inhibition. In support of this hypothesis preliminary experiments showed NOS inhibition with L-NNA (N-omega-nitro-L-arginine) increases tumor necrosis, 1 day after administration, in our HCT-116 tumor model.

Topics: Animals; Antineoplastic Agents; Carbon Dioxide; Cell Hypoxia; Cells, Cultured; Dose-Response Relationship, Drug; Endothelial Cells; Endothelium, Vascular; Enzyme Inhibitors; HCT116 Cells; Humans; Mice; Mice, Inbred C3H; Mice, Inbred NOD; Mice, SCID; Necrosis; Neoplasms, Experimental; Nitric Oxide Synthase; Nitroarginine; Oxygen; Regional Blood Flow; Time Factors; Tirapazamine; Triazines

The effect of ZD6126 on tumor oxygen tension and tumor growth delay in combination with ionizing radiation was examined in the human U87 glioblastoma tumor model. Resistance to ZD6126 treatment was investigated with the nitric oxide synthase inhibitor, l-N(G)-nitroarginine methyl ester (hydrochloride; l-NAME/active form, l-NNA).. U87 human xenografts were grown in athymic nude mice. ZD6126 was given with or without l-NNA. Tumor oxygen tension was measured using the Oxford Oxylite (Oxford, England) fiberoptic probe system. Tumor volume was determined by direct measurement with calipers and calculated by the formula [(smallest diameter(2) x widest diameter)/2].. Multiple doses of ZD6126 treatment (three doses) had a significant effect on tumor growth delay, reducing the average daily tumor growth rate from 29% to 16%. When given 1 hour before radiation, ZD6126 caused an acute increase in hypoxia in U87 tumors, and reduced tumor growth delay compared with that of radiation alone. The combination of ZD6126 given after radiation, either as a single dose or in multiple doses, had greater or similar antitumor activity compared with radiation alone. Twenty-four hours after administration, a single dose of ZD6126 induced little (10 +/- 8%) necrosis in U87 xenografts. l-NNA, when given in combination with ZD6126, significantly enhanced the effectiveness of ZD6126 in inducing tumor necrosis.. Our observation that ZD6126-induced tumor hypoxia can decrease radiation response when ZD6126 is given prior to radiation indicates the importance of scheduling. Our findings suggest that the optimal therapeutic benefit of ZD6126 plus radiation in human glioblastoma may require multiple dosing in combination with a nitric oxide synthase inhibitor, to be scheduled following radiotherapy.

Topics: Angiogenesis Inhibitors; Animals; Blood Vessels; Brain Neoplasms; Combined Modality Therapy; Drug Therapy, Combination; Enzyme Inhibitors; Glioblastoma; Humans; Hypoxia; Mice; Mice, Nude; Necrosis; Neovascularization, Pathologic; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Organophosphorus Compounds; Oxygen; Radiation Tolerance; Radiation, Ionizing; Transplantation, Heterologous; Tumor Cells, Cultured; Vascular Endothelial Growth Factor A

The goal of this study was to investigate the role of cardiac nerves on the response to 90-minute coronary artery stenosis (CAS), which reduced coronary blood flow by 40% for 90 minutes, and subsequent myocardial stunning after reperfusion in chronically instrumented conscious pigs. In pigs with regional cardiac denervation (CD), myocardial stunning was intensified, ie, at 12 hours reperfusion wall thickening (WT) was depressed more, P<0.05, in CD (-46+/-5%) as compared with intact pigs (-31+/-3%) and remained depressed in CD at 24 hours reperfusion (-45+/-6%). Although the TTC technique was negative for infarct, histopathological analysis revealed patchy necrosis present in 11+/-2% of the area at risk. In intact pigs, WT had essentially recovered at 24 hours without infarct. In CD pigs treated with either an antioxidant, N-2-mercaptopropionyl glycine (MPG, 100 mg/kg per hour) or systemic nitric oxide synthase inhibition using N(omega)-nitro-L-arginine (L-NA, 30 mg/kg for 3 days), recovery of wall thickening was similar to that in pigs with intact nerves and without evidence of infarct. Immunohistochemistry analysis for 3-nitrotyrosine in tissue after CAS and 1 hour reperfusion demonstrated enhanced peroxynitrite-related protein nitration in pigs with regional CD compared with pigs with intact cardiac nerves, and pigs with regional CD and MPG or L-NA. Thus, reperfusion after myocardial ischemia in the setting of CD results in enhanced stunning and development of infarct. The underlying mechanism appears to involve nitric oxide and reactive oxygen species.

Topics: Animals; Coronary Stenosis; Denervation; Enzyme Inhibitors; Heart; Hemodynamics; Immunohistochemistry; Models, Animal; Myocardial Reperfusion; Myocardial Stunning; Myocardium; Necrosis; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Norepinephrine; Reactive Oxygen Species; Swine; Tyrosine

We have investigated the role of nitric oxide (NO) as mediator of the secondary growth of a traumatic cortical necrosis. For this purpose, a highly standardized focal lesion of the brain was induced in 46 Sprague-Dawley rats by cold injury. Twenty-four hours later--the timepoint of maximal lesion spread--the animals were sacrificed and brains were removed for histomorphometry of the maximal necrosis area and volume. The animals were divided into five experimental groups. Group I received the NO donor L-arginine as i.v. bolus 10 min prior to trauma (300 mg/kg body weight; n = 10) and a second bolus of the same dosage intraperitoneally 1 h after trauma. Group II (n = 10)--serving as control of group I--was infused with an i.v. bolus of 1 mL/kg isotonic saline 10 min prior to and a subsequent bolus i.p. 1 h after trauma. Group III (n = 8) received 100 mg/kg b.w. of the inducible NOS (iNOS) inhibitor aminoguanidine (AG) 1 h before and 8 h after trauma by intraperitoneal route. Group IV was administered with the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine (L-NNA; 100 mg/kg b.w., i.p.; n = 8); group V--the controls of group III and IV--was administered with isotonic saline (1 mL/kg b.w. i.p.; n = 10) 1 h before and 8 h after trauma. In the control group with i.v./i.p. sham treatment (II), the focal lesion led to a cortical necrosis with a maximum area of 3.1 +/- 0.3 mm2 and a lesion volume of 5.7 +/- 0.5 mm3 at 24 h after trauma. In animals with administration of L-arginine, the focal lesion had a maximum area of 3.1 +/- 0.3 mm2 and a volume of 5.3 +/- 0.5 mm3. Hence, the NO donor did not affect the secondary growth of necrosis. Animals with i.p. sham treatment (group V) had a maximal lesion area of 3.6 +/- 0.2 mm2 and lesion volume of 6.2 +/- 0.4 mm3. Administration of aminoguanidine afforded significant attenuation of the lesion growth. Accordingly, the maximal area of necrosis spread only to 2.8 +/- 0.2 mm2 with a volume of 4.5 +/- 0.5 mm3, respectively, at 24 h after trauma (p < 0.01 vs group V). On the other hand, administration of L-NNA did not influence the maximal lesion area (3.7 +/- 0.2 mm2) or lesion volume (6.5 +/- 0.5 mm3) evolving at 24 h after trauma. Thus, neither the enhancement of the formation of NO by L-arginine nor gross inhibition of the synthesis of NO by L-NNA did affect the secondary spread of the necrosis from a focal trauma. The marked attenuation of the posttraumatic necrosis growth by the iNOS inhibitor aminoguanidin

Topics: Animals; Arginine; Brain; Brain Injuries; Cold Temperature; Enzyme Inhibitors; Guanidines; Male; Necrosis; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Rats; Rats, Sprague-Dawley; Time Factors

Impaired vascular responsiveness in sepsis may lead to maldistribution of blood flow in organs. We hypothesized that increased production of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) mediates the impaired dilation to ACh in sepsis. Using a 24-h cecal ligation and perforation (CLP) model of sepsis, we measured changes in arteriolar diameter and in red blood cell velocity (V(RBC)) in a capillary fed by the arteriole, following application of ACh to terminal arterioles of rat hindlimb muscle. Sepsis attenuated both ACh-stimulated dilation and V(RBC) increase. In control rats, arteriolar pretreatment with the NO donors S-nitroso-N-acetylpenicillamine or sodium nitroprusside reduced diameter and V(RBC) responses to a level that mimicked sepsis. In septic rats, arteriolar pretreatment with the "selective" iNOS blockers aminoguanidine (AG) or S-methylisothiourea sulfate (SMT) restored the responses to the control level. The putative neuronal NOS (nNOS) inhibitor 7-nitroindazole also restored the response toward control. At 24-h post-CLP, muscles showed no reduction of endothelial NOS (eNOS), elevation of nNOS, and, surprisingly, no induction of iNOS protein; calcium-dependent constitutive NOS (eNOS+nNOS) enzyme activity was increased whereas calcium-independent iNOS activity was negligible. We conclude that 1) AG and SMT inhibit nNOS activity in septic skeletal muscle, 2) NO could impair vasodilative responses in control and septic rats, and 3) the source of increased endogenous NO in septic muscle is likely upregulated nNOS rather than iNOS. Thus agents released from the blood vessel milieu (e.g., NO produced by skeletal muscle nNOS) could affect vascular responsiveness.

Topics: Acetylcholine; Animals; Arterioles; Enzyme Inhibitors; Lactic Acid; Male; Muscle, Skeletal; Necrosis; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitrites; Nitroarginine; Nitroprusside; Penicillamine; Rats; Rats, Sprague-Dawley; Sepsis; Vasodilation

We examined whether nitric oxide (NO) inhibition during moderate reduction in coronary blood flow (CBF) would affect perfusion-contraction matching. Coronary stenosis (CS) was induced in conscious pigs, which resulted in a stable 39 +/- 1% reduction in CBF for 1.5 h. Ischemic zone wall thickening (IZWT) decreased by an average of 56 +/- 2% during CS from 2.7 +/- 0.2 mm. After reperfusion, myocardial stunning was observed, but this recovered without evidence of necrosis. After recovery and subsequent administration of systemic NO synthase inhibition (N(omega)-nitro-L-arginine, 25 mg. kg(-1). day(-1) x 3 days), CS for 1.5 h reduced CBF similarly but decreased IZWT significantly more, P < 0.05, by 89 +/- 5%. Myocardial stunning, i.e., the decrease in IZWT at 12 h post-CS, was more severe (-65 +/- 5% vs. -21 +/- 3%), P < 0.05. Furthermore, CS during NO synthase inhibition resulted in multifocal subendocardial areas of necrosis in the area at risk. These data suggest that in the intact, conscious pig, NO inhibition prevents perfusion-contraction matching, resulting in intensification of post-ischemic stunning and development of subendocardial necrosis.

Topics: Animals; Coronary Circulation; Coronary Disease; Hemodynamics; Myocardial Contraction; Myocardial Ischemia; Myocardial Reperfusion; Myocardial Stunning; Necrosis; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Swine

Glyoxal, methylglyoxal (MG), and 3-deoxyglucosone (3-DG) are physiological alpha-oxoaldehydes formed by lipid peroxidation, glycation, and degradation of glycolytic intermediates. They are enzymatically detoxified in cells by the cytosolic glutathione-dependent glyoxalase system (glyoxal and MG only) and by NADPH-dependent reductase and NAD(P)+-dependent dehydrogenase. In this study, the changes in the cellular and extracellular concentrations of these alpha-oxoaldehydes were investigated in murine P388D1 macrophages during necrotic cell death induced by median toxic concentrations of hydrogen peroxide and 1-chloro-2,4-dinitrobenzene (CDNB). Alpha-oxoaldehyde concentrations were determined by derivatization with 1,2-diamino-4,5-dimethoxybenzene. There were relatively small increases in cellular and extracellular glyoxal concentration, except that extracellular glyoxal was decreased with hydrogen peroxide. The cytosolic concentration of 3-DG and the cytosolic and extracellular concentrations of MG, however, increased markedly. Aminoguanidine inhibited alpha-oxoaldehyde accumulation and prevented cytotoxicity induced by hydrogen peroxide and CDNB. The accumulation of glyoxal and MG in toxicant-treated cells was a likely consequence of decreased in situ activity of glyoxalase 1. The effect was marked for MG but not for glyoxal, suggestive of a greater metabolic flux of MG formation than of glyoxal. The accumulation of 3-DG in toxicant-treated cells was probably due to the decreased availability of pyridine nucleotide cofactors for the detoxification of 3-DG. Impairment of alpha-oxoaldehyde detoxification is cytotoxic, and this may contribute to toxicity associated with GSH oxidation and S conjugation in oxidative stress and chemical toxicity, and to chronic pathogenesis associated with diabetes mellitus where there is oxidative stress and the formation of glyoxal, MG, and 3-DG is increased.

Topics: Animals; Cell Line; Cell Survival; Deoxyglucose; Dinitrochlorobenzene; Glutathione; Glyoxal; Guanidines; Hydrogen Peroxide; Macrophages; Mice; Necrosis; Nitroarginine; Oxidative Stress; Pyruvaldehyde

A free radical gas, nitric oxide, has many useful functions when produced under physiological conditions by neurons and endothelial cells. However, excess nitric oxide has been reported to exert cytotoxic effects by direct toxicity or by reaction with superoxide. The effect of nitric oxide on the microcirculation in the periphery of a flap remains unclear, and its effect on flap survival is also unknown because nitric oxide has a dual action. Thus, we attempted to clarify the effect of nitric oxide on survival of rat random pattern skin flaps by the use of an endothelial constitutive nitric oxide synthase inhibitor (i.p. administration of 50 mg/kg N(G)-nitro-L-arginine) and the substrate of nitric oxide synthase (i.p. administration of 1 g/kg L-arginine). Three kinds of experiments were done using a total number of 120 animals: (1) time course measurement of blood flow in the flap periphery was performed using a laser Doppler flowmeter (30 rats), (2) the length of the surviving area of flaps was measured 1 week after raising the flap (60 rats), and (3) Western blot analysis was used to determine the time course of changes in the amount of endothelial constitutive nitric oxide synthase and the formation of 3-nitro-L-tyrosine, which is a marker of peroxynitrite-mediated (i.e., nitric oxide-dependent) tissue damage (30 rats). Inhibition of endothelial constitutive nitric oxide synthase by N(G)-nitro-L-arginine significantly decreased the length of the surviving area of skin flap (p < 0.01 compared with the control), which was associated with a decrease in the blood flow of the proximal portion of the flap. On the other hand, exogenous L-arginine increased the survival length of skin flap significantly (p < 0.01 compared with the control), which was associated with an increase in blood flow of the distal portion of the flap even though there was nitric oxide-mediated oxidative tissue damage. These results suggest that nitric oxide produced by endothelial constitutive nitric oxide synthase plays a role in maintaining circulation in the skin flap periphery and that L-arginine administration contributes to reduction of ischemic necrosis in the skin flap.

Topics: Animals; Arginine; Blotting, Western; Endothelium, Vascular; Enzyme Inhibitors; Free Radicals; Graft Survival; Injections, Intraperitoneal; Ischemia; Laser-Doppler Flowmetry; Male; Microcirculation; Necrosis; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidation-Reduction; Rats; Rats, Wistar; Regional Blood Flow; Skin; Skin Transplantation; Tyrosine

1. To observe the effect of nitric oxide (NO) on the myocardium, the NO synthesis inhibitor NG-nitro-L-arginine (L-NNA) was administered to hypercholesterolaemic stroke-prone spontaneously hypertensive (SHRSP) rats. 2. Hypercholesterolaemic SHRSP were produced by feeding SHRSP a high fat and high cholesterol diet (HFC) for 2 weeks. The rats were then divided into three groups: (i) the N group, which were fed the HFC diet containing 0.023% L-NNA and 1% NaCl in their drinking water (n = 10); (ii) the NH group, which were fed the HFC diet containing 0.023% L-NNA and 1% NaCl in their drinking water which also contained 80 mg/L hydralazine (n = 10); and (iii) the C group, which were fed the HFC diet and 1% NaCl in their drinking water (n = 10). 3. All rats in the N and NH groups died within 35 days of the initiation of L-NNA administration. Rats in the N and NH groups had significantly increased serum creatine phosphokinase, lactate dehydrogenase, glutamic oxaloacetic transaminase and serum total cholesterol levels compared with rats in the C group. 4. Fibrosis in response to necrosis was histopathologically observed in the hearts of all rats in the N and NH groups without exception. Occlusion or intimal thickening in the arteries adjacent to the necrotic regions was also observed. 5. These results suggest that nitric oxide deficiency induces myocardial infarction in hypercholesterolaemic SHRSP. These NO-deficient hypercholesterolaemic SHRSP offer a new model of myocardial infarction in rats.

Topics: Animals; Blood Pressure; Cerebrovascular Disorders; Coronary Vessels; Enzyme Inhibitors; Fibrosis; Hydralazine; Hypercholesterolemia; Male; Myocardial Infarction; Myocardium; Necrosis; Nitric Oxide; Nitroarginine; Rats; Rats, Inbred SHR

1. L-2-Chloropropionic acid (L-CPA) produces selective neuronal cell necrosis in rat cerebellum when administered orally at 750 mg kg-1 that is mediated in part through activation of N-methyl-D-aspartate (NMDA) receptors. Cerebellar granule cell death occurs between 30 and 36 h following L-CPA administration exhibiting a number of features in common with excitatory amino acid-induced cell death. We have used this in vivo model to examine the neurochemical processes following L-CPA-induced activation of NMDA receptors leading to neuronal cell death in the rat cerebellum. 2. The effects of a number of compounds which potently block nitric oxide synthase in vitro were examined on L-CPA-induced neurotoxicity 48 h following L-CPA dosing, to discover whether the neuronal cell death is mediated in part by excessive nitric oxide generation. Four inhibitors were studied, NG-nitro-L-arginine (L-NOARG), NG-nitro-L-arginine methyl ester (L-NAME), NG-iminoethyl-L-ornithine (L-NIO) and 3-bromo-7-nitroindazole (BrNI). 3. L-NAME (50 mg kg-1, i.p. twice daily) and BrIN (50 mg kg-1, i.p. twice daily) administration prevented the L-CPA-induced loss of granule cells which can reach up to 80-90% of the total cell number in rats treated with L-CPA alone. L-NOARG (50 mg kg-1, i.p. twice daily) and L-NIO administered at either 25 or 100 mg kg-1, twice daily did not produce any significant protection against L-CPA-induced neurotoxicity. 4. Both L-NAME and BrIN also prevented the L-CPA-induced increase in cerebellar water content and sodium concentrations. L-NIO when administered at the highest doses prevented the increase in cerebellar sodium concentration but not water content. L-NIO and L-NOARG were ineffective in preventing the L-CPA-induced increases in cerebellar water and sodium concentrations. 5. L-CPA-induced reductions in cerebellar aspartate and glutamate concentrations and increases in glutamine and GABA concentrations were prevented by L-NAME and BrIn, but not by L-NIO or L-NOARG. Also reductions in L-[3H]-glutamate binding to glutamate ionotrophic and metabotrophic receptors in the granule cell layer of rat cerebellum was prevented by L-NAME and BrIN, but not L-NIO or L-NOARG. 6. In conclusion, the neuroprotection offered by L-NAME and BrIN suggests that L-CPA-induced cerebellar granule cell necrosis is possibly mediated by or associated with excessive generation of nitric oxide. The inability of nitric oxide synthase inhibitors, L-NOARG and L-NIO to afford protectio

Topics: Animals; Aspartic Acid; Cerebellum; gamma-Aminobutyric Acid; Glutamic Acid; Glutamine; Hydrocarbons, Chlorinated; In Vitro Techniques; Indazoles; Male; Necrosis; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitroarginine; Ornithine; Propionates; Rats

We investigated the putative role of nitric oxide in the expression of neuronal injury following both transient severe forebrain ischemia (CA1 neuronal injury) and transient or permanent middle cerebral artery occlusion (neocortical pannecrosis). Using the four-vessel occlusion model and increasing doses of N-omega-nitro-L-arginine, 2-40 mg/kg, we were unable to demonstrate any reduction in the percentage of CA1 cells injured following 10 min of transient severe forebrain ischemia followed by seven days of reperfusion. Higher doses proved toxic insofar as they increased the mortality following the ischemic insult. Saline-treated animals (n = 8) had 77 +/- 10% CA1 injury while those treated with 2 mg/kg of nitro-arginine i.v. had 80 +/- 7% (n = 7), and those with 10 mg/kg i.v. had 78 +/- 11% (n = 8). Two of five rats given 20 mg/kg i.v., three of eight given 40 mg/kg i.v., and two of six given 10 mg/kg i.v. followed by 3 x 10 mg/kg i.p., died. Of those treated with high-dose nitro-arginine and which survived ischemia and seven days' reperfusion, no significant reduction in CA1 injury was detected. Wistar rats and spontaneously hypertensive rats treated with either saline or nitro-arginine i.v. were exposed to 2 h of transient middle cerebral artery occlusion followed by 22 h of reperfusion. There were seven animals in each group. Wistars treated with saline had 198 +/- 67 mm3 (mean +/- S.D.) of neocortical infarction, and those treated with 10 m/kg of nitro-arginine i.v. had 199 +/- 93 mm3. Spontaneously hypertensive rats, transiently ischemic, treated with saline had 164 +/- 25 mm3 of infarct volume, while those treated with 2 mg/kg i.v. had 151 +/- 53 mm3, and those treated with 10 mg/kg i.v. had 145 +/- 29 mm3. Animals treated with 40 mg/kg i.v. had a nonsignificantly larger mean infarct volume (191 +/- 81 mm3). High dose nitro-arginine caused an increase in hypertension in the spontaneously hypertensive rats and increased the severity of focal ischemia as measured by intra-ischemic regional cerebral blood flows. A final group of seven spontaneously hypertensive rats underwent permanent middle cerebral artery occlusion and repeated dosing with N-omega-nitro-L-arginine i.p. In these animals an infarct volume of 234 +/- 60 mm3 was observed, which was again not statistically different from saline-treated controls (208 +/- 43 mm3, n = 7).(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Blood Gas Analysis; Blood Pressure; Cell Death; Cerebral Arteries; Cerebral Infarction; Ischemic Attack, Transient; Male; Necrosis; Neurons; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Inbred SHR; Rats, Wistar

There is clinical and experimental evidence to indicate that cigarette smoking may increase the risk of skin ischemic necrosis in flap surgery but the pathogenic mechanism remains unclear. The objectives of this project were to investigate the potential deleterious effects and mechanism of action of nicotine, a major by-product of cigarette smoking, in skin flap surgery in the pig. It was observed that 4-5 weeks of intramuscular nicotine injections (4 mg/kg; twice daily) significantly (p < 0.05) decreased the skin flap capillary blood flow and the length and area of skin flap viability in the pig. This nicotine treatment also induced a 1.6-fold increase in skin flap tissue content of norepinephrine compared with the saline-treated control. The estimated mean wet skin tissue content of norepinephrine (5 x 10(-7) M) was much higher than the circulating level of norepinephrine (1.8 x 10(-9) M) in nicotine-treated pigs. This level of norepinephrine (5 x 10(-7) M) was seen to induce a significant vasoconstrictor effect (75% increase over basal perfusion pressure) in isolated perfused pig skin flaps. It was also observed that the vasoconstrictor effect of norepinephrine was significantly (p < 0.05) enhanced in the presence of 10(-4) M N omega-monomethyl-L-arginine or NG-nitro-L-arginine, an endothelium-derived relaxing factor--nitric oxide (EDRF/NO) synthesis inhibitor. This vasoconstrictor effect was further enhanced in the presence of NG-nitro-L-arginine and 10(-5) M indomethacin, a cyclooxygenase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Pressure; Body Temperature; Cardiac Output; Catecholamines; Dermatologic Surgical Procedures; Ischemia; Microcirculation; Necrosis; Nicotine; Nitric Oxide; Nitroarginine; Norepinephrine; omega-N-Methylarginine; Regional Blood Flow; Skin; Surgical Flaps; Swine

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

N omega-nitro-L-arginine (0.3-10 mg/kg), a nitric oxide (NO) synthase inhibitor, was administered i.p. to gerbils subjected to 10 min of carotid artery occlusion seven times at 5 min, 3, 6, 24, 48, 72 and 96 h after recirculation. Histopathological examination of the brains obtained 6 days after reflow disclosed that N omega-nitro-L-arginine possesses an ability to mitigate neuronal necrosis in the CA1 subfield of the hippocampus with an optimal dosage of 3 mg/kg. These results strongly suggest that NO synthase activation is at least partly involved in the pathogenetic cellular mechanisms underlying selective neuronal necrosis following cerebral ischemia.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Dose-Response Relationship, Drug; Gerbillinae; Hippocampus; Image Processing, Computer-Assisted; Injections, Intraperitoneal; Ischemic Attack, Transient; Male; Necrosis; Neurons; Nitric Oxide Synthase; Nitroarginine

Antitumour agents such as flavone acetic acid, xanthenone acetic acid (XAA), 5,6-dimethylxanthenone-4-acetic acid and tumour necrosis factor-alpha, following single dose administration to mice with colon 38 adenocarcinomas, induce tumour haemorrhagic necrosis and an elevation in plasma nitrate. The relationship between these two effects has been studied using firstly a series of methyl-substituted XAA derivatives with varying antitumour activity, and secondly the inhibitors NG-monomethyl-L-arginine (NMMA), N-nitro-L-arginine (NNA) and canavanine, which affect nitric oxide synthesis. Elevation of plasma nitrate resulting from the oxidation of L-arginine by nitric oxide synthase is inhibited by NNA rather than by NMMA or canavanine. The results demonstrate that tumour necrosis can be induced in the absence of a significant elevation of plasma nitrate.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Arginine; Canavanine; Colonic Neoplasms; Flavonoids; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Inbred Strains; Necrosis; Nitrates; Nitric Oxide; Nitroarginine; omega-N-Methylarginine; Xanthenes; Xanthones