nitroarginine and Disease-Models--Animal

Gastrointestinal motility is crucial to gut health and has been associated with different disorders such as inflammatory bowel diseases and postoperative ileus. Despite rat and mouse being the two animal models most widely used in gastrointestinal research, minimal studies in rats have investigated gastrointestinal motility. Therefore, our study provides a comparison of colonic motility in the mouse and rat to clarify species differences and assess the relative effectiveness of each animal model for colonic motility research. We describe the protocol modifications and optimization undertaken to enable video imaging of colonic motility in the rat. Apart from the broad difference in terms of gastrointestinal diameter and length, we identified differences in the fundamental histology of the proximal colon such that the rat had larger villus height-to-width and villus height-to-crypt depth ratios compared with mouse. Since gut motility is tightly regulated by the enteric nervous system (ENS), we investigated how colonic contractile activity within each rodent species responds to modulation of the ENS inhibitory neuronal network. Here we used

Topics: Animals; Colon; Disease Models, Animal; Enteric Nervous System; Gastrointestinal Motility; Mice; Myenteric Plexus; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley

Here we describe mechanistically distinct enzymes (a kinase, a guanosine triphosphatase, and a ubiquitin protein hydrolase) that function in disparate biochemical pathways and can also act in concert to mediate a series of redox reactions. Each enzyme manifests a second, noncanonical function-transnitrosylation-that triggers a pathological biochemical cascade in mouse models and in humans with Alzheimer's disease (AD). The resulting series of transnitrosylation reactions contributes to synapse loss, the major pathological correlate to cognitive decline in AD. We conclude that enzymes with distinct primary reaction mechanisms can form a completely separate network for aberrant transnitrosylation. This network operates in the postreproductive period, so natural selection against such abnormal activity may be decreased.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cyclin-Dependent Kinase 5; Cysteine; Disease Models, Animal; Dynamins; HEK293 Cells; Humans; Mice; Mice, Transgenic; Mutation; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidation-Reduction; Protein Processing, Post-Translational; Synapses; Ubiquitin Thiolesterase

Acute lung injury (ALI) is a pulmonary disease that acts as a severe acute inflammatory response with no specific drugs. iNOS, a catalyst of the excessive production of NO, has been demonstrated to participate in the inflammatory process, and targeting iNOS may be a promising therapeutic pathway to alleviate ALI. In our research, eighteen new disubstituted benzoxazolone derivatives were synthesized, characterized, and evaluated for activity against NO production in an LPS-induced RAW264.7 cell. The results showed that these compounds could obviously inhibit the over-generation of NO and disubstitution at the 4, N-position of the benzoxazolone ring, presenting better potency than substitution only at the 4-position. Among the analogues generated, compounds 2c, 2d, and 3d showed NO inhibitory activity with IC

Topics: Acute Lung Injury; Animals; Anti-Inflammatory Agents; Benzoxazoles; Disease Models, Animal; Drug Design; Edema; Gene Expression Regulation; Interleukin-1beta; Interleukin-6; Lipopolysaccharides; Lung; Macrophages; Mice; Nitric Oxide; Nitric Oxide Synthase Type II; Peroxidase; RAW 264.7 Cells

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

Parkinson's disease (PD) is a common neurodegenerative disorder which is mostly sporadic but familial-linked PD (FPD) cases have also been found. The first reported gene mutation that linked to PD is α-synuclein (α-syn). Studies have shown that mutations, increased expression or abnormal processing of α-syn can contribute to PD, but it is believed that multiple mechanisms are involved. One of the contributing factors is post-translational modification (PTM), such as phosphorylation of α-syn at serine 129 by G-protein-coupled receptor kinases (GRKs) and casein kinase 2α (CK2α). Another known important contributing factor to PD pathogenesis is oxidative and nitrosative stress. In this study, we found that GRK6 and CK2α can be S-nitrosylated by nitric oxide (NO) both in vitro and in vivo. S-nitrosylation of GRK6 and CK2α enhanced their kinase activity towards the phosphorylation of α-syn at S129. In an A53T α-syn transgenic mouse model of PD, we found that increased GRK6 and CK2α S-nitrosylation were observed in an age dependent manner and it was associated with an increased level of pSer129 α-syn. Treatment of A53T α-syn transgenic mice with Nω-Nitro-L-arginine (L-NNA) significantly reduced the S-nitrosylation of GRK6 and CK2α in the brain. Finally, deletion of neuronal nitric oxide synthase (nNOS) in A53T α-syn transgenic mice reduced the levels of pSer129 α-syn and α-syn in an age dependent manner. Our results provide a novel mechanism of how NO through S-nitrosylation of GRK6 and CK2α can enhance the phosphorylation of pSer129 α-syn in an animal model of PD.

Topics: Age Factors; alpha-Synuclein; Animals; Casein Kinase II; Disease Models, Animal; G-Protein-Coupled Receptor Kinases; Gene Deletion; HEK293 Cells; Humans; Mice; Mice, Transgenic; Mutation; Nitric Oxide; Nitric Oxide Synthase Type I; Nitroarginine; Nitrosative Stress; Parkinson Disease; Phosphorylation; Serine

There is a major clinical need for new therapies for the treatment of chronic itch. Many of the molecular components involved in itch neurotransmission are known, including the neuropeptide NPPB, a transmitter required for normal itch responses to multiple pruritogens in mice. Here, we investigated the potential for a novel strategy for the treatment of itch that involves the inhibition of the NPPB receptor NPR1 (natriuretic peptide receptor 1). Because there are no available effective human NPR1 (hNPR1) antagonists, we performed a high-throughput cell-based screen and identified 15 small-molecule hNPR1 inhibitors. Using in vitro assays, we demonstrated that these compounds specifically inhibit hNPR1 and murine NPR1 (mNPR1). In vivo, NPR1 antagonism attenuated behavioral responses to both acute itch- and chronic itch-challenged mice. Together, our results suggest that inhibiting NPR1 might be an effective strategy for treating acute and chronic itch.

Topics: Animals; Behavior, Animal; Cell-Free System; Dermatitis, Contact; Disease Models, Animal; Ganglia, Spinal; Humans; Mice, Inbred C57BL; Mice, Knockout; Neurons; Pruritus; Receptors, Atrial Natriuretic Factor; Reproducibility of Results; Signal Transduction; Small Molecule Libraries

Male Sprague-Dawley rats (n=5- 6 per group) were treated with the irreversible tryptophan hydroxylase inhibitor, DL-4-p-chlorophenylalanine (pCPA, 150mg/kg, i.p.), to achieve central serotonin-depletion followed by repeated exposures to restraint stress and were then subjected to the FST. 24, 5 and 1h prior to the test, animals were treated with either L-NA (10mg/kg, i.p.), TRIM (50mg/kg, i.p.) or saline vehicle (1mg/kg i.p).. pCPA treatment coupled with restraint stress increased immobility in the FST compared to naïve controls. Both NOS inhibitors decreased immobility time in 5-HT depleted and stressed animals only in keeping with their antidepressant-like properties. Brain regions analyzed for c-FOS immunoreactivity included the pre-limbic cortex, lateral septum (LS), nucleus accumbens, paraventricular hypothalamic nucleus (PVN), central amygdala, hippocampus (dorsal dentate gyrus and ventral CA1), and the dorsal raphe nucleus (DRN). Exposure to the FST increased c-FOS immunoreactivity in the LS, PVN, dentate gyrus, vCA1 and the DRN when compared to non-FST exposed controls. FST-induced c-FOS immunoreactivity was further increased in the LS following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. By contrast, FST-induced c-FOS immunoreactivity was reduced in dorsal dentate gyrus, vCA1 and the DRN following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. There was no difference observed in FST-induced expression of c-FOS between naïve animals and animals exposed to pCPA and restraint stress. This combination however provoked an increase in FosB/ΔFosB immunoreactivity in the infra-limbic cortex and nucleus accumbens with a concomitant reduction in the lateral septum, suggesting alterations to long-term, adaptive neuronal activation.. This study identified a pattern of enhanced and reduced FST-related c-FOS immunoreactivity indicative of a NO-regulated network where inhibition of NO leads to activation of the septum with concomitant inhibition of the hippocampus, and the DRN. No link between FST-induced regional expression of c-FOS and increased immobility in the FST was observed in animals exposed to pCPA and stress. However, the 5-HT depletion regime combined with restraint stress provoked regional changes in the expression of ΔFosB which may relate to increased immobility in the FST.

Topics: Analysis of Variance; Animals; Brain; Cell Count; Depression; Disease Models, Animal; Enzyme Inhibitors; Leucine; Male; Nitroarginine; Polymethacrylic Acids; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Restraint, Physical; Serotonin; Statistics, Nonparametric; Swimming

Colonic electrical stimulation (CES) may have a therapeutic potential for slow transit constipation (STC). This study aimed to evaluate the effects of implantable CES on gastrointestinal transit and defecation, and explore its mechanisms in a canine STC model.. Two pairs of electrodes were implanted in each of the proximal colon and rectosigmoid junction (RSJ). Parameters were individualized according to the symptoms of the stimulated dogs. In the STC model, gastrointestinal transit and defecation were assessed to evaluate the effects of double-site CES, and of double-site CES combined with atropine or N-nitro-L-arginine (L-NNA) in a crossover design.. Individualized parameters varied among the animals. The CES significantly shortened gastrointestinal transit time (GITT) and colonic transit time (CTT) compared with sham CES (p = 0.001 and p < 0.001, respectively). Compared with sham CES, the CES also exhibited significantly higher stool frequency and stool consistency score (p = 0.018 and p = 0.001, respectively). Co-treatment with atropine or L-NNA blocked the effects of CES on GITT, CTT, and stool consistency. The stool frequency increased by CES, however, only reduced by co-treatment with L-NNA.. This double-site implantable CES can improve the gastrointestinal transit and defecation in a canine STC model, possibly by activating the cholinergic and nitrergic pathways. The CES mode used in this study may be proven feasible in treating STC.

Topics: Analysis of Variance; Animals; Atropine; Cholinergic Agents; Colon; Constipation; Defecation; Disease Models, Animal; Dogs; Electric Stimulation; Electrodes, Implanted; Enzyme Inhibitors; Female; Gastrointestinal Diseases; Gastrointestinal Transit; Muscarinic Antagonists; Nitroarginine; Radiography

We have previously reported antidepressant effect of Cnestis ferruginea (CF) in behavioral models of depression. Due to the promise shown by this extract, this study was carried out to investigate the contribution of monoaminergic, cholinergic and nitrergic systems to the antidepressant-like effect elicited by CF.. Male albino mice were pretreated with monoaminergic or cholinergic receptor antagonists, L-arginine or N(G)-nitro-L-arginine (nitric oxide synthase inhibitor) (at doses reported to block the in vivo effect of the agonists), 15 min before oral administration of CF (100 mg/kg), 1 h later, the forced swim test (FST) in mice was carried out.. CF treatment produced significant changes in the duration of swimming (F(5,42)=9.86, P<0.001), climbing behaviour (F(5,42)=4.51, P=0.004) and mean time spent immobile (F(5,42)=11.55, P<0.001) vs. vehicle-treated control. Co-administration of CF with fluoxetine or imipramine potentiated their effect. However, pretreatment of mice with reserpine (F(1,16)=119.20, P<0.001), prazosin (F(1,16)=68.98, P<0.001), sulpiride (F(1,16)=15.46, P<0.01), RS 127445 ((F(1,20)=8.22, P<0.01), SB 399885 ((F(1,20)=38.44, P<0.001), atropine (F(1,16)=53.77, P<0.001), or L-arginine (nitric oxide precursor) (F(1,16)=10.35, P<0.01) prevented CF-induced antidepressant-like effect in mice. In addition, pretreatment of mice with L-NNA (10 mg/kg) augmented the effect of CF.. C. ferruginea exerts its antidepressant-like action through interaction with α-adrenoceptor, dopamine D2, 5-HT2B, 5-HT6 and muscarinic cholinergi1c receptors as well as L-arginine-nitric oxide systems. C. ferruginea could be used as adjuvant with conventional antidepressants in the treatment of major depressive disorder.

Topics: Animals; Antidepressive Agents; Arginine; Behavior, Animal; Cholinergic Antagonists; Connaraceae; Depression; Disease Models, Animal; Male; Medicine, African Traditional; Mice; Motor Activity; Nigeria; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Plant Extracts; Rats; Rats, Sprague-Dawley; Receptors, Cholinergic; Signal Transduction; Swimming

Alkaloids from Ba lotus seeds (ABLS) are a kind of important functional compounds in lotus seeds. The present study was designed to determine its hypertension prophylactic effects in the L-NNA-induced mouse hypertension model. The mice were treated with ABLS, the serum and tissues levels of NO, MDA, ET-1, VEGF, and CGRP were determined using the experimental kits, the mRNA levels of various genes in the heart muscle and blood vessel tissues were further determined by RT-PCR assay. ABLS could reduce the systolic blood pressure (SBP), mean blood pressure (MBP), and diastolic blood pressure (DBP), compared to that of the model control group. After ABLS treatment, the NO (nitric oxide) contents in serum, heart, liver, kidney and stomach of the mice were higher than that of the control mice, but the MDA (malonaldehyde) contents were lower than that of the control mice. The serum levels of ET-1 (endothelin-1), VEGF (vascular endothelial growth factor) were decreased after ABLS treatment, but CGRP (calcium gene related peptide) level was increased. The ABLS treated mice had higher mRNA expressions of HO-1, nNOS, and eNOS and lower expressions of ADM, RAMP2, IL-1β, TNF-α, and iNOS than the control mice. Higher concentration of ABLS had greater prophylactic effects, which were close to that of the hypertension drug captopril. These results indicated the hypertension prophylactic effects of ABLS could be further explored as novel medicine or functional food in the future.

Topics: Alkaloids; Animals; Blood Pressure; Disease Models, Animal; Humans; Hypertension; Interleukin-1beta; Male; Mice; Mice, Inbred ICR; Nitroarginine; Nymphaeaceae; Seeds; Tumor Necrosis Factor-alpha; Vascular Endothelial Growth Factor A

Endothelial dysfunction occurs in conduit and cerebral resistance arteries with advancing age. Lifelong caloric restriction (CR) can prevent the onset of age-related dysfunction in many tissues, but its effects on cerebral resistance artery function, as compared with conduit artery function, have not been determined. We measured endothelium-dependent dilation (EDD) in the carotid artery and middle cerebral artery (MCA) from young (5-7 months), old ad libitum fed (AL, 29-32 months), and old lifelong CR (CR, 40 % CR, 29-32 months) B6D2F1 mice. Compared with young, EDD for old AL was 24 % lower in the carotid and 47 % lower in the MCA (p < 0.05). For old CR, EDD was not different from young in the carotid artery (p > 0.05), but was 25 % lower than young in the MCA (p < 0.05). EDD was not different between groups after NO synthase inhibition with N(ω)-nitro-L-arginine methyl ester in the carotid artery or MCA. Superoxide production by the carotid artery and MCA was greater in old AL compared with young and old CR (p < 0.05). In the carotid, incubation with the superoxide scavenger TEMPOL improved EDD for old AL (p > 0.05), with no effect in young or old CR (p > 0.05). In the MCA, incubation with TEMPOL or the NADPH oxidase inhibitor apocynin augmented EDD in old AL (p < 0.05), but reduced EDD in young and old CR (p < 0.05). Thus, age-related endothelial dysfunction is prevented by lifelong CR completely in conduit arteries, but only partially in cerebral resistance arteries. These benefits of lifelong CR on EDD result from lower oxidative stress and greater NO bioavailability.

Topics: Aging; Animal Feed; Animals; Caloric Restriction; Carotid Arteries; Cerebrovascular Circulation; Cerebrovascular Disorders; Disease Models, Animal; Electron Spin Resonance Spectroscopy; Endothelium, Vascular; Follow-Up Studies; Male; Mice; Middle Cerebral Artery; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidative Stress; Time Factors; Vascular Resistance; Vasodilation

We previously reported the cancer chemopreventive activity of 4'-geranyloxyferulic acid (GOFA, Miyamoto et al., Nutr Cancer 2008; 60:675-84) and a β-cyclodextrin inclusion compound of GOFA (Tanaka et al., Int J Cancer 2010; 126:830-40) in colitis-related colorectal carcinogenesis. In our study, the chemopreventive effects of a newly synthesized GOFA-containing compound, GOFA-N(omega)-nitro-L-arginine methyl ester (L-NAME), which inhibits inducible nitric oxide (iNOS) and cyclooxygenase-2 (COX) enzymes, were investigated using a colitis-associated mouse colorectal carcinogenesis model with azoxymethane (AOM) and dextran sodium sulfate (DSS). The dietary administration of GOFA-L-NAME after the AOM and DSS treatments significantly reduced the multiplicity of adenocarcinomas (inhibition rates: 100 ppm, 84%, p < 0.001; 500 ppm, 94%, p < 0.001) compared with the AOM + DSS group. Dietary GOFA-L-NAME significantly decreased the proliferation (p < 0.001) and increased the apoptosis (p < 0.001) of colonic adenocarcinoma cells. A subsequent short-term experiment revealed that dietary GOFA-L-NAME decreased the mRNA expression of inflammatory enzymes, such as iNOS and COX-2, and proinflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and macrophage inflammatory protein (MIP)-2 in the colonic mucosa of mice that received 1.5% DSS in their drinking water for 7 days. Our findings indicate that GOFA-L-NAME is able to inhibit colitis-associated colon carcinogenesis by modulating inflammation, proliferation, apoptosis and the expression of proinflammatory cytokines in mice.

Topics: Adenocarcinoma; Adenoma; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Carcinogenesis; Cell Proliferation; Colorectal Neoplasms; Coumaric Acids; Cyclooxygenase 2; Cytokines; Disease Models, Animal; Gene Expression Regulation, Neoplastic; Inflammation; Intestinal Mucosa; Male; Mice; Mice, Inbred ICR; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type II; Nitroarginine; RNA-Binding Proteins

We have previously validated the use of L-nitro-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, to induce placental hypoperfusion in a rabbit model. Here, the effects of L-NAME on placental vascularization were explored. Transplacental transfer of L-NAME and/or its active metabolite, NG-nitro-L-arginine (L-NOARG), was evaluated.. 25 pregnant female rabbits were allocated on day 24 to one of 5 groups: L-NAME groups (31.35, 62.5, 125 and 250 mg/kg/day) or Control group (C). On Day 28, the labyrinthine area was analyzed for stereology and gene expression. L-NAME and L-NOARG were quantified in maternal and fetal blood.. The volume density of fetal vessels was significantly decreased in L-NAME (including 62.5-250 mg/kg/day which induced an IUGR) compared to C groups. L-NAME induced an increase of the volume and surface density of the maternal blood space. The trophoblast volume density remained unchanged as well as the surface density of fetal vessels. Relative expression of eNOS, VEGFA, VEGFR-1 and VEGFR-2 in placentas was not affected by 125 mg/kg/day L-NAME treatment, whereas IGF-2 expression was significantly increased in this L-NAME group compared to C. L-NAME was not detected in maternal nor fetal plasma. In contrast, fetal to maternal L-NOARG ratio was 100% in all L-NAME groups.. These data demonstrate that L-NAME induced placental hypovascularization. The active L-NOARG metabolite is found in maternal and fetal plasma at similar concentrations. This could impact the fetal growth and reduces the interest of this model to study fetal outcomes of placental hypoperfusion.

Topics: Animals; Disease Models, Animal; Female; Fetal Growth Retardation; Gene Expression; Maternal-Fetal Exchange; Neovascularization, Physiologic; NG-Nitroarginine Methyl Ester; Nitroarginine; Placenta; Pregnancy; Rabbits

Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical tests and in the current investigation the brain penetrant NOS inhibitor N(ω)-nitro-L-arginine (l-NA) and the preferential inhibitor of neuronal NOS (nNOS) 1-(2-trifluoromethylphenyl) imidazole (TRIM) were assessed in the olfactory bulbectomised (OB) rat, a well-established animal model of depression. Magnetic resonance imaging (MRI) was employed to assess regional brain volumes, blood perfusion and T1 and T2 relaxometry times both with and without drug treatment. l-NA (10 mg/kg, once daily p.o. for 10 days) attenuated OB-related hyperactivity in the "open field" test in a comparable fashion to the tricyclic antidepressant imipramine (20 mg/kg, once daily p.o. for 14 days) indicative of an antidepressant-like response in the model. Treatment with TRIM (50 mg/kg, once daily s.c.) attenuated OB-related hyperactivity following 7 days of treatment when compared to vehicle treated controls. OB is associated with enlarged ventricular volume, increased periventicular perfusion and a decrease in T2 relaxation times in cortical and hippocampal regions, with enhanced perfusion and reduced T2 times attenuated by L-NA treatment. L-NA treatment was also associated with an increase in T1 relaxation times in limbic and cortical regions and found to reduce resting state hippocampal blood perfusion in OB animals. Behavioural observations are consistent with an antidepressant action of NOS inhibitors where associated changes in perfusion and T2 relaxation times may be related to the antidepressant action of L-NA in the model.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Cytokines; Depression; Disease Models, Animal; Enzyme Inhibitors; Exploratory Behavior; Locomotion; Magnetic Resonance Imaging; Male; Nitric Oxide Synthase; Nitroarginine; Olfactory Bulb; Rats; Rats, Sprague-Dawley; Spin Labels; Time Factors

Alterations in the NO pathway play an important role in the development of convulsive seizures via the glutamatergic and GABAergic systems in acute pentylenetetrazole (PTZ) seizure animals. We previously reported that the background NO levels under physiological conditions negatively regulate convulsive seizures, while excess NO levels under pathologic conditions positively regulate PTZ-induced convulsive seizures. In this study, the NO content in various brain regions after a single dose injection of PTZ was quantitatively and directly measured using the ex vivo X-band electron paramagnetic resonance method with an NO-trapping agent. Experimental data demonstrated the effects of NO on the convulsive seizure threshold: a 1.5-fold increase in the NO level in all brain regions compared to that observed in the control state showed proconvulsive properties without any involvement with nonconvulsive seizures. The distribution of the background NO content in the normal animals was higher in the temporal region of the cerebral cortex, including the amygdala, than in the hippocampus, cerebellum and other regions of the cerebral cortex. However, the levels of NO after the occurrence of acute PTZ-induced convulsive seizures significantly increased by more than 50% in all brain regions, thus suggesting that the NO levels in all brain regions contribute to PTZ-induced convulsions as a seizure threshold. In a pharmacological study, the inhibitor of neuronal NO synthase and antagonists of ionotropic glutamate receptors prevented PTZ-induced convulsions and excessive NO generation. In addition, therapeutic drugs, such as valproate and ethosuximide used to treat generalized seizures not only inhibited the increase in NO generation induced by PTZ, but also prevented both convulsive and nonconvulsive seizures caused by PTZ. We herein provide novel insight into the involvement of NO in PTZ-seizure susceptibility at the whole-animal level.

Topics: Analysis of Variance; Animals; Brain; Convulsants; Disease Models, Animal; Dose-Response Relationship, Drug; Electron Spin Resonance Spectroscopy; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Male; Mice; Mice, Inbred ICR; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase Type I; Nitroarginine; Pentylenetetrazole; Seizures

Vascular pathology is a major feature of Alzheimer's disease (AD) and other dementias. We recently showed that chronic administration of the target-of-rapamycin (TOR) inhibitor rapamycin, which extends lifespan and delays aging, halts the progression of AD-like disease in transgenic human (h)APP mice modeling AD when administered before disease onset. Here we demonstrate that chronic reduction of TOR activity by rapamycin treatment started after disease onset restored cerebral blood flow (CBF) and brain vascular density, reduced cerebral amyloid angiopathy and microhemorrhages, decreased amyloid burden, and improved cognitive function in symptomatic hAPP (AD) mice. Like acetylcholine (ACh), a potent vasodilator, acute rapamycin treatment induced the phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and NO release in brain endothelium. Administration of the NOS inhibitor L-NG-Nitroarginine methyl ester reversed vasodilation as well as the protective effects of rapamycin on CBF and vasculature integrity, indicating that rapamycin preserves vascular density and CBF in AD mouse brains through NOS activation. Taken together, our data suggest that chronic reduction of TOR activity by rapamycin blocked the progression of AD-like cognitive and histopathological deficits by preserving brain vascular integrity and function. Drugs that inhibit the TOR pathway may have promise as a therapy for AD and possibly for vascular dementias.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Anti-Bacterial Agents; Brain; Disease Models, Animal; Enzyme Activation; Enzyme Inhibitors; Humans; Memory; Mice; Mice, Transgenic; Nitric Oxide; Nitric Oxide Synthase Type III; Nitroarginine; Phosphorylation; Sirolimus; Vasodilation

Chronic kidney disease (CKD) is a global problem. Slowing CKD progression is a major health priority. Since CKD is characterized by complex derangements of homeostasis, integrative animal models are necessary to study development and progression of CKD. To study development of CKD and novel therapeutic interventions in CKD, we use the 5/6th nephrectomy ablation model, a well known experimental model of progressive renal disease, resembling several aspects of human CKD. The gross reduction in renal mass causes progressive glomerular and tubulo-interstitial injury, loss of remnant nephrons and development of systemic and glomerular hypertension. It is also associated with progressive intrarenal capillary loss, inflammation and glomerulosclerosis. Risk factors for CKD invariably impact on endothelial function. To mimic this, we combine removal of 5/6th of renal mass with nitric oxide (NO) depletion and a high salt diet. After arrival and acclimatization, animals receive a NO synthase inhibitor (NG-nitro-L-Arginine) (L-NNA) supplemented to drinking water (20 mg/L) for a period of 4 weeks, followed by right sided uninephrectomy. One week later, a subtotal nephrectomy (SNX) is performed on the left side. After SNX, animals are allowed to recover for two days followed by LNNA in drinking water (20 mg/L) for a further period of 4 weeks. A high salt diet (6%), supplemented in ground chow (see time line Figure 1), is continued throughout the experiment. Progression of renal failure is followed over time by measuring plasma urea, systolic blood pressure and proteinuria. By six weeks after SNX, renal failure has developed. Renal function is measured using 'gold standard' inulin and para-amino hippuric acid (PAH) clearance technology. This model of CKD is characterized by a reduction in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), hypertension (systolic blood pressure>150 mmHg), proteinuria (> 50 mg/24 hr) and mild uremia (>10 mM). Histological features include tubulo-interstitial damage reflected by inflammation, tubular atrophy and fibrosis and focal glomerulosclerosis leading to massive reduction of healthy glomeruli within the remnant population (<10%). Follow-up until 12 weeks after SNX shows further progression of CKD.

Topics: Animals; Disease Models, Animal; Glomerular Filtration Rate; Male; Nephrectomy; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Inbred Lew; Renal Insufficiency, Chronic; Sodium Chloride, Dietary

Remote ischemic postconditioning (RIPoC) attenuates ischemia/reperfusion (I/R) injury in the heart, lung and hind limb. RIPoC performed in the hind limb reduces brain injury following focal cerebral ischemia in rats. Whether RIPoC has a neuroprotective effect with respect to global cerebral I/R injury is, however, unknown, and the mechanism of neuroprotection needs further elucidation. Here we investigated whether RIPoC could reduce global cerebral I/R injury in rats and whether this neuroprotective effect was induced by up-regulating endothelial nitric oxide synthase (eNOS) through the phosphatidylinositol-3 kinase/Akt (PI3K/Akt) pathway. Global cerebral ischemia was performed via 8min of four-vessel occlusion. Neuronal density, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells and expression of Bcl-2 and Bax in the hippocampal CA1 region were assessed after reperfusion. Morris water maze task was used to quantify spatial learning and memory deficits after reperfusion. The expression of eNOS, phosphorylated eNOS (Ser1177), Akt and phosphorylated Akt (Ser473) in the CA1 region was measured after reperfusion. RIPoC significantly attenuated delayed neuronal death and reduced the spatial learning and memory deficits associated with global cerebral ischemia. Pre-administration of N(ω)-nitro-l-arginine methyl ester (a nonselective NOS inhibitor) significantly abolished the neuroprotective effect of RIPoC. Moreover, pre-administration of LY294002 (a highly selective inhibitor of PI3K) not only significantly reversed the neuroprotective effect of RIPoC, but also obviously inhibited the up-regulation of eNOS induced by RIPoC. Our findings suggest that RIPoC protects the brain against global cerebral I/R injury and that this neuroprotection is mediated by up-regulating eNOS through the PI3K/Akt pathway.

Topics: Analysis of Variance; Animals; Avoidance Learning; Brain; Brain Infarction; Brain Ischemia; Cell Death; Chromones; Disease Models, Animal; Enzyme Inhibitors; Gene Expression Regulation; In Situ Nick-End Labeling; Ischemic Postconditioning; Male; Maze Learning; Morpholines; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type III; Nitroarginine; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinase; Rats; Rats, Sprague-Dawley; Reaction Time; Reperfusion Injury

The leaves of Taxus chinensis var. mairei (Taxaceae) is used traditionally to fill pillows in some rural areas of China. Its volatile substances have been speculated to be capable of improving sleep quality, making blood pressure stable, and having diuretic capacity as recorded in Ancient Chinese Materia Medica. Using animal models and new technologies, we confirmed the hypotensive potential of volatile components from leaves of Taxus chinensis var. mairei (VCLT).. VCLT was obtained by supercritical CO(2) extraction equipment from Taxus chinensis var. mairei fresh leaves. Hypertensive rats were pre-induced by intraperitoneal (i,p.) injection of Nω-Nitro-l-Ariginine (l-NNA) for 15 days (15mg/kg, twice a day), then divided into 5 groups and subjected to the following treatments. l-NNA group (group 1) receiving l-NNA alone (15mg/kg, i.p., twice per day for 6 weeks); in addition to receiving l-NNA same as group 1, Hydrochlorothiazide (HDZ) group (group 2) receiving HDZ (orally administration, 5mg/kg, once per day for 6 weeks); VCLT groups (groups 3-5), including VCLT1, VCLT2, VCLT3. The VCLT rats were housed in an enclosed cage (2 rats/0.064m(3)). VCLT was mixed well and sprayed on fresh leaves surface of Taxus chinensis var. mairei (100ml/kg) with three dosages: 167g/kg (VCLT1), 233g/kg (VCLT2) and 333g/kg (VCLT3), respectively. Systolic Blood Pressure (SBP), plasma nitric oxide (NO), plasma angiotensin II, postprandial blood glucose, fasting blood glucose and blood lipids were determined.. VCLT prevented the increase of SBP and plasma angiotensin II in l-NNA treated rats. Although VCLT does not significantly reduce blood triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C), it decreases total cholesterol (TC) while increasing plasma NO levels in a dose-dependent manner.. VCLT can be used as a natural and supplementary reagents for the treatment of hypertension.

Topics: Administration, Oral; Angiotensin II; Animals; Antihypertensive Agents; Biomarkers; Blood Glucose; Blood Pressure; Chromatography, Supercritical Fluid; Disease Models, Animal; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Hydrochlorothiazide; Hypertension; Lipids; Male; Nitric Oxide; Nitroarginine; Phytotherapy; Plant Leaves; Plants, Medicinal; Rats; Rats, Sprague-Dawley; Taxus; Time Factors; Volatilization

Emodin is traditionally used as a laxative and is found to increase or decrease the contractility of intestinal smooth muscle in low doses and high doses, respectively. In this study, we propose that bidirectional regulation (BR) on the contractility of jejunal smooth muscle (CJSM) is inducible by emodin in the absence of control by the central nervous system. The results indicated that emodin-induced BR had the following characteristics. A stimulatory effect on CJSM was induced by emodin at 7 low contractile states, and an inhibitory effect was induced on CJSM at 7 high contractile states. Emodin-induced BR on myosin phosphorylation was also observed. BR was not observed in the presence of tetrodotoxin, suggesting that enteric nervous system is required for producing BR. The stimulatory effect of emodin on CJSM was abolished by atropine and diphenhydramine, respectively, suggesting that BR was correlated with cholinergic and histamine system while jejunal smooth muscle was at low contractile state. The inhibitory effect of emodin on CJSM was abolished by phentolamine, propranolol, and L-NG-nitroarginine (L-NNA), respectively, suggesting that BR was related to adrenergic hyperactivity and with a nitric oxide relaxing mechanism while jejunal smooth muscle was in a high contractile state. The exact mechanism, however, needs further investigation.

Topics: Animals; Atropine; Constipation; Diarrhea; Diphenhydramine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Emodin; Enteric Nervous System; In Vitro Techniques; Jejunum; Laxatives; Muscle Contraction; Muscle, Smooth; Myosins; Nitroarginine; Phentolamine; Phosphorylation; Propranolol; Rats; Rats, Sprague-Dawley; Tetrodotoxin

It has been reported that endothelin-1 (ET-1) overproduction and reduced nitric oxide (NO) production are closely related to the progression of renal diseases. In the present study, we examined the interrelation between ET-1 and NO system using rats treated with the combination of deoxycorticosterone acetate (DOCA)-salt and a non selective NO synthase inhibitor N(ω)-nitro-L-arginine (NOARG).. Rats were treated with DOCA-salt (15 mg/kg, plus drinking water containing 1% NaCl) for two weeks, and then additional treatment of NOARG (0.6 mg/ml in the drinking water) was performed for three days.. Combined treatment of DOCA-salt and NOARG drastically developed the severe renal dysfunction and tissue injury. This treatment additionally enhanced renal ET-1 production compared to the rats treated with DOCA-salt alone, whereas a selective ET(A) receptor antagonist ABT-627 completely prevented renal dysfunction and tissue injury. On the other hand, combined treatment of DOCA-salt and NOARG induced the phosphorylation of inhibitory protein kappa B (IκB), followed by the activation of nuclear factor-kappa B (NF-κB) in the kidney. In addition, pyrrolidine-dithiocarbamate completely suppressed not only NF-κB activation but also renal dysfunction and ET-1 overproduction.. These results suggest that NF-κB/ET-1/ET(A) receptor-mediated actions are responsible for the increased susceptibility to DOCA-salt induced renal injuries in the case of reduced NO production.

Topics: Animals; Atrasentan; Desoxycorticosterone; Disease Models, Animal; Disease Susceptibility; Endothelin-1; Hypertension; Kidney Diseases; Male; NF-kappa B; Nitric Oxide; Nitroarginine; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Severity of Illness Index; Sodium Chloride, Dietary; Thiocarbamates

Renal prostacycline (PGI(2)) and oxidative stress are known to be important factors that effect the natriurezis and diuresis. 8-iso prostaglandin F(2)α± (8-isoprostane), a member of F(2)-isoprostanes, is formed from the nonenzymatic reaction of arachidonic acid and oxygen radicals in vivo and in vitro, and also it is a marker of oxidative stress in vivo. The aim of this study is to determine the role of renal PGI(2) and 8-isoprostane in a salt and nitric oxide (NO) inhibition-induced hypertension model. Rats were distributed equally among four groups (n = 6 per group). Control rats were given normal salt diet (0.32%); high-salt (HS) rats were given high salt diet (3.2%); NG-nitro-L-arginine (L-NNA) rats were given normal salt diet and 25 mg/kg L-NNA; HS+L-NNA rats were given high salt diet and 25 mg/kg L-NNA. Rats were placed in individual metabolic cages for 17 days. Systolic blood pressure (SBP) was measured at days initial, 7th and 14th .Urinary 8-isoprostane and PGI(2) levels were analyzed. Salt- loading alone did not change SBP values. The average SBP in L-NNA and HS+L-NNA groups were shown to significantly enhance compared to initial and day 7th in the same groups, respectively. The levels of 8-isoprostane in the HS+L-NNA group was significantly enhanced compared to the other groups. L-NNA or HS diet alone did not change the levels of 8-isoprostane compared to the control group. L-NNA alone did not change PGI(2) levels in urine compared to the control. PGI(2) levels in the HS, and the HS+L-NNA group was significantly higher compared to the control group. This study concluded that NOS inhibition plus salt-loading induced oxidative stress and increased renal PGI(2). Also, it is suggested that augmented oxidative stress may aggravate the hypertension. But the renal synthesis of PGI(2) is increased in order to augment the diuresis and natriuresis without the effect of blood pressure (BP).

Topics: Animals; Dinoprost; Disease Models, Animal; Enzyme Inhibitors; Epoprostenol; Hypertension; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidative Stress; Rats; Rats, Sprague-Dawley; Sodium Chloride, Dietary

The objective of this study was to determine the effects of 7-nitroindazole (7NI--a preferential neuronal nitric oxide synthase (NOS) inhibitor) and NG-nitro-L-arginine (NNA--a non-selective NOS inhibitor) on the anticonvulsant action of pregabalin (PGB--a third-generation antiepileptic drug) in the maximal electroshock (MES)-induced seizure model in mice. Electroconvulsions were produced in mice by means of an alternating current (50 Hz, 500 V, 25 mA, ear-clip electrodes, 0.2 s stimulus duration, tonic hindlimb extension taken as the endpoint). The anticonvulsant action of PGB in the MES test was expressed as median effective doses (ED50 values) of the drug, protecting 50% of animals tested against MES-induced seizures. The acute adverse-effect potentials of PGB in combination with 7NI and NNA were evaluated in the chimney test (motor coordination), step-through passive avoidance task (long-term memory) and grip-strength test (skeletal muscular strength) in mice. 7NI (50 mg/kg, ip) significantly enhanced the anticonvulsant action of PGB by reducing the ED50 value of PGB from 145.0 mg/kg to 74.4 mg/kg (p<0.01). Similarly, 7NI at the lower dose of 25 mg/kg also potentiated the anticonvulsant action of PGB by lowering the ED50 value of PGB from 145.0 mg/kg to 117.9 mg/kg, although the results did not attain statistical significance. In contrast, NNA (40 mg/kg, ip) had no impact on the anticonvulsant effects of PGB. Moreover, none of the examined combinations of PGB with 7NI and NNA affected motor coordination, long-term memory and skeletal muscular strength in mice. Based on this preclinical study, one can conclude that 7NI significantly enhanced and NNA had no effect on the anticonvulsant activity of PGB against MES-induced seizures in mice.

Topics: Animals; Anticonvulsants; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Electroshock; Enzyme Inhibitors; gamma-Aminobutyric Acid; Indazoles; Male; Mice; Neuroprotective Agents; Nitroarginine; Pregabalin; Seizures; Toxicity Tests, Acute

Hypercapnia has been reported to modify liver circulation. The vascular regulations implicated in this response remain partly unknown.. Using anesthetized and ventilated rabbits, we designed this study to evaluate the hepatic artery and portal vein blood flow velocity adjustments (20 MHz pulsed Doppler) after changes in PaCO2 (by varying the inspiratory fraction of CO2 and to assess the proper role of pH, independent of PaCO2 changes, the role of portal vein CO2, and the effect of nitric oxide synthase inhibition on CO2-induced modifications of hepatic hemodynamics.. Increasing PaCO2 from 30.9 +/- 5 mm Hg to 77 +/- 11 mm Hg increased arterial blood pressure by 20% (P < 0.01) and hepatic artery blood flow velocity by 90% (P < 0.05) and decreased aortic blood flow velocity by 15% and portal vein blood flow velocity by 40% (both P < 0.05). Changes in pH (1 mL of 0.1 N hydrochloric acid infusion) or isolated changes in portal vein CO2 at constant PaCO2 induced by CO2 insufflation in an open abdomen had no effect on hepatic hemodynamics. Pretreatment with a nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine (2.5 mg/kg), blunted the systemic response to hypercapnia, whereas the portal modifications persisted, with a largely attenuated hepatic artery blood flow increase.. CO2 per se acts on hepatic blood flow by its systemic effect, probably via chemoreflexes. Nitric oxide does not mediate hepatosplanchnic hemodynamic modifications to acute changes in PaCO2 but may play a permissive role by regulating the amplitude of hepatic vascular response.

Topics: Animals; Blood Flow Velocity; Blood Pressure; Carbon Dioxide; Disease Models, Animal; Enzyme Inhibitors; Hemodynamics; Hepatic Artery; Hydrogen-Ion Concentration; Hypercapnia; Liver; Liver Circulation; Male; Nitric Oxide Synthase; Nitroarginine; Portal Vein; Rabbits; Respiration, Artificial; Vasoconstriction

Glucocorticoid-induced hypertension is associated with imbalance between nitric oxide (NO) and superoxide. One of the pathways that causes this imbalance is endothelial NO synthase (eNOS) uncoupling. In the present study, adrenocorticotrophic hormone (ACTH)- and dexamethasone-treated rats were further treated with sepiapterin, a precursor of tetrahydrobiopterin, or N-nitro-L-arginine (NOLA), an inhibitor of NOS, to investigate the role of eNOS uncoupling in glucocorticoid-induced hypertension.. Male Sprague-Dawley (SD) rats (n = 7-13/group) were treated with either sepiapterin (5 mg/kg/day, IP) or saline (sham) 4 days before and during ACTH (0.2 mg/kg/day, SC), dexamethasone (0.03 mg/kg/day, SC), or saline treatment. NOLA (0.4 mg/ml in drinking water) was given to rats 4 days before and during dexamethasone treatment. Systolic blood pressure (SBP) was measured by the tail-cuff method.. Both ACTH (116 +/- 2 to 135 +/- 3 mm Hg (mean +/- s.e.m.), P < 0.001) and dexamethasone (114 +/- 4 to 133 +/- 3 mm Hg, P < 0.0005) increased SBP. Sepiapterin alone did not alter SBP. Sepiapterin did not prevent ACTH- (129 +/- 4 mm Hg, NS) or dexamethasone-induced hypertension (135 +/- 3 mm Hg, NS), although plasma total biopterin concentrations were increased. NOLA increased SBP in rats prior to dexamethasone or saline treatment. NOLA further increased SBP in both saline- (133 +/- 4 to 157 +/- 3 mm Hg, P < 0.05) and dexamethasone-treated rats (135 +/- 5 to 170 +/- 6 mm Hg, P < 0.05). ACTH and dexamethasone increased plasma F(2)-isoprostane concentrations. Neither sepiapterin nor NOLA significantly affected this marker of oxidative stress.. Sepiapterin did not prevent ACTH- or dexamethasone-induced hypertension. NOLA exacerbated dexamethasone-induced hypertension. These data suggest that eNOS uncoupling does not play a major role in the genesis of glucocorticoid-induced hypertension in the rat.

Topics: Adrenocorticotropic Hormone; Animals; Biomarkers; Biopterins; Blood Pressure; Dexamethasone; Dietary Supplements; Disease Models, Animal; Enzyme Inhibitors; F2-Isoprostanes; Hypertension; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Oxidative Stress; Pterins; Rats; Rats, Sprague-Dawley

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor can enhance endothelial nitric oxide synthase expression and induce vasodilatation. The vasodilatory effect may be detrimental to portal-systemic collaterals due to aggravating the shunting degrees. The present study investigated the effects of pravastatin, a HMG-CoA reductase inhibitor, on the collateral vascular responsiveness to endothelin-1 (ET-1) and portal-systemic shunting in portal hypertensive rats.. The partial portal vein-ligated (PVL) rats received either pravastatin (25 mg/kg per day) or distilled water since 2 days prior to until 7 days after ligation. On the 8(th) day following hemodynamic measurements, the collateral vascular responsiveness to ET-1 was evaluated by an in situ collateral perfusion model. The shunting degrees of collaterals were evaluated by constructing vascular flow-pressure curves and color microsphere study, respectively. PVL rats underwent pre-incubation with: (i) Krebs solution (control); or Krebs solution plus (ii) 2 x 10(-5) M pravastatin; (iii) pravastatin + N(omega)-nitro-L-arginine (10(-4) M); and (iv) pravastatin + indomethacin (10(-5) M), followed by ET-1 (10(-10)-10(-7) M) administration to evaluate the collateral vascular responsiveness.. In chronic study, pravastatin did not modify systemic and portal hemodynamics and collateral vascular responsiveness to ET-1. The resistances of flow-pressure curves and the microsphere study demonstrated similar shunting degrees between both groups. Furthermore, pravastatin pre-incubation didn't reduce collateral perfusion pressure to ET-1.. Chronic pravastatin administration does not induce detrimental effects on hemodynamics and collaterals in PVL rats, nor does it influence the shunting degree. In addition, it does not modify the vasoconstrictive effect of ET-1 on the collaterals of PVL rats.

Topics: Animals; Collateral Circulation; Cyclooxygenase Inhibitors; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Enzyme Inhibitors; Hemodynamics; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypertension, Portal; Indomethacin; Male; Nitric Oxide Synthase; Nitroarginine; Portal System; Pravastatin; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Time Factors; Vascular Resistance; Vasoconstriction; Vasoconstrictor Agents

To investigate the effects of NG-nitro-L-arginine (L-NA) on pulmonary surfactant (PS) and pulmonary cells apoptosis in lipopolysaccharide (LPS) induced acute lung injury (ALI).. Twenty-four male Sprague-Dawley (SD) rats were randomly divided into three groups: control group, model group, L-NA group. Model of ALI was reproduced by injection of LPS 5 mg/kg via sublingual vein in model group and L-NA group. L-NA (20 mg/kg) was administered in L-NA group, while normal saline was administered in control group and model group 3 hours after LPS injection. The rats were sacrificed at 6 hours after LPS injection, and the lung tissue was obtained for measuring the expressions of pulmonary surfactant protein A (SP-A) mRNA by in situ hybridization (ISH) method; meanwhile, apoptosis rate was evaluated by flow cytometry; the expression of caspase-3 was evaluated by Western blotting analysis; Bcl-2 and Bax were evaluated respectively by immunohistochemistry (IHC).. Compared with that of the control group, SP-A mRNA [absorbance (A) value] in the lung tissue was significantly decreased by LPS (0.071+/-0.017 vs. 0.113+/-0.021) in model group, apoptosis rate of pulmonary cells [(25.04+/-4.57)% vs. (11.37+/-3.08)%], caspase-3 protein expression (A value: 298.64+/-37.11 vs. 110.24+/-14.35) and Bax protein expression (A value: 0.145+/-0.011 vs. 0.076+/-0.010) were significantly increased, Bcl-2 protein expression (A value: 0.064+/-0.011 vs. 0.073+/-0.009) and Bcl-2/Bax (0.447+/-0.086 vs. 0.976+/-0.157) were decreased in model group (all P<0.01). L-NA was given at 3 hours after LPS administration, the expressions of SP-A mRNA (A value: 0.085+/-0.015) and Bcl-2 protein (A value: 0.070+/-0.087) increased markedly, compared with model group (P<0.01 and P<0.05), but there were no significant changes in the pulmonary cells apoptosis rate [(20.67+/-1.35)%], caspase-3 protein expression (A value: 268.75+/-42.56), Bax protein expression (A value: 0.142+/-0.012) and Bcl-2/Bax (0.498+/-0.069) between L-NA group and model group (all P>0.05).. L-NA had no effect on LPS-induced pulmonary cell apoptosis and had no effect on the expressions of caspase-3 and Bax, but L-NA can protect the lung from LPS-induced injury by up-regulating the expression of PS.

Topics: Acute Lung Injury; Animals; Apoptosis; bcl-2-Associated X Protein; Caspase 3; Disease Models, Animal; Lipopolysaccharides; Lung; Male; Nitroarginine; Pulmonary Surfactants; Rats; Rats, Sprague-Dawley

We recently developed a rat model of cardiorenal failure that is characterized by severe left ventricular systolic dysfunction (LVSD) and low nitric oxide (NO) production that persisted after temporary low-dose NO synthase inhibition. We hypothesized that LVSD was due to continued low NO availability and might be reversed by supplementing NO. Rats underwent a subtotal nephrectomy and were treated with low-dose NO synthase inhibition with N(ω)-nitro-l-arginine up to week 8. After 3 wk of washout, rats were treated orally with either the long-acting, tolerance-free NO donor molsidomine (Mols) or vehicle (Veh). Cardiac and renal function were measured on weeks 11, 13, and 15. On week 16, LV hemodynamics and pressure-volume relationships were measured invasively, and rats were killed to quantify histological damage. On week 15, blood pressure was mildly reduced and creatinine clearance was increased by Mols (both P < 0.05). Mols treatment improved ejection fraction (53 ± 3% vs. 37 ± 2% in Veh-treated rats, P < 0.001) and stroke volume (324 ± 33 vs. 255 ± 15 μl in Veh-treated rats, P < 0.05). Rats with Mols treatment had lower end-diastolic pressures (8.5 ± 1.1 mmHg) than Veh-treated rats (16.3 ± 3.5 mmHg, P < 0.05) and reduced time constants of relaxation (21.9 ± 1.8 vs. 30.9 ± 3.3 ms, respectively, P < 0.05). The LV end-systolic pressure-volume relationship was shifted to the left in Mols compared with Veh treatment. In summary, in a model of cardiorenal failure with low NO availability, supplementing NO significantly improves cardiac systolic and diastolic function without a major effect on afterload.

Topics: Administration, Oral; Animals; Biomarkers; Cardiotonic Agents; Creatinine; Disease Models, Animal; Gene Expression Regulation; Kidney Diseases; Male; Molsidomine; Myocardial Contraction; Myocardium; Nephrectomy; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Rats; Rats, Inbred Lew; Stroke Volume; Time Factors; Tyrosine; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Pressure

Impaired gastric accommodation and gastric dysrhythmia are common in gastroparesis and functional dyspepsia. Recent studies have shown that synchronized gastric electrical stimulation (SGES) accelerates gastric emptying and enhances antral contractions in dogs. The aim of this study was to investigate the effects and mechanism of SGES on gastric accommodation and slow waves impaired by vagotomy in dogs. Gastric tone, compliance, and accommodation as well as slow waves with and without SGES were assessed in seven female regular dogs and seven dogs with bilateral truncal vagotomy, chronically implanted with gastric serosal electrodes and a gastric cannula. We found that 1) vagotomy impaired gastric accommodation that was normalized by SGES. The postprandial increase in gastric volume was 283.5 +/- 50.6 ml in the controlled dogs, 155.2 +/- 49.2 ml in the vagotomized dogs, and 304.0 +/- 57.8 ml in the vagotomized dogs with SGES. The ameliorating effect of SGES was no longer observed after application of N(omega)-nitro-L-arginine (L-NNA); 2) vagotomy did not alter gastric compliance whereas SGES improved gastric compliance in the vagotomized dogs, and the improvement was also blocked by L-NNA; and 3) vagotomy impaired antral slow wave rhythmicity in both fasting and fed states. SGES at the proximal stomach enhanced the postprandial rhythmicity and amplitude (dominant power) of the gastric slow waves in the antrum. In conclusion, SGES with appropriate parameters restores gastric accommodation and improves gastric slow waves impaired by vagotomy. The improvement in gastric accommodation with SGES is mediated via the nitrergic pathway. Combined with previously reported findings (enhanced antral contractions and accelerated gastric emptying) and findings in this study (improved gastric accommodation and slow waves), SGES may be a viable therapy for gastroparesis.

Topics: Animals; Compliance; Disease Models, Animal; Dogs; Electric Stimulation Therapy; Enzyme Inhibitors; Fasting; Female; Gastric Dilatation; Gastric Emptying; Gastroparesis; Muscle Contraction; Nitrergic Neurons; Nitric Oxide Synthase; Nitroarginine; Periodicity; Postprandial Period; Stomach; Vagotomy

Several clinical studies have shown the beneficial cardiovascular effects of fibrates in patients with diabetes and insulin resistance. The ligands of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) reduce ischemia-reperfusion injury in nondiabetic animals. We hypothesized that the activation of PPAR-alpha would exert cardioprotection in type 2 diabetic Goto-Kakizaki (GK) rats, involving mechanisms related to nitric oxide (NO) production via the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. GK rats and age-matched Wistar rats (n >or= 7) were given either 1) the PPAR-alpha agonist WY-14643 (WY), 2) dimethyl sulfoxide (DMSO), 3) WY and the NO synthase inhibitor N(G)-nitro-l-arginine (l-NNA), 4) l-NNA, 5) WY and the PI3K inhibitor wortmannin, or 6) wortmannin alone intravenously before a 35-min period of coronary artery occlusion followed by 2 h of reperfusion. Infarct size (IS), expression of endothelial NO synthase (eNOS), inducible NO synthase, and Akt as well as nitrite/nitrate were determined. The IS was 75 +/- 3% and 72 +/- 4% of the area at risk in the Wistar and GK DMSO groups, respectively. WY reduced IS to 56 +/- 3% in Wistar (P < 0.05) and to 46 +/- 5% in GK rats (P < 0.001). The addition of either l-NNA or wortmannin reversed the cardioprotective effect of WY in both Wistar (IS, 70 +/- 5% and 65 +/- 5%, respectively) and GK (IS, 66 +/- 4% and 64 +/- 4%, P < 0.05, respectively) rats. The expression of eNOS and eNOS Ser1177 in the ischemic myocardium from both strains was increased after WY. The expression of Akt, Akt Ser473, and Akt Thr308 was also increased in the ischemic myocardium from GK rats following WY. Myocardial nitrite/nitrate levels were reduced in GK rats (P < 0.05). The results suggest that PPAR-alpha activation protects the type 2 diabetic rat myocardium against ischemia-reperfusion injury via the activation of the PI3K/Akt and NO pathway.

Topics: Androstadienes; Animals; Blood Glucose; Body Weight; Cardiotonic Agents; Diabetes Mellitus, Type 2; Disease Models, Animal; Enzyme Inhibitors; Hemodynamics; Insulin; Male; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; PPAR alpha; Proto-Oncogene Proteins c-akt; Pyrimidines; Rats; Rats, Wistar; Signal Transduction; Wortmannin

Schizophrenia symptoms can be segregated into positive, negative and cognitive, which exhibit differential sensitivity to drug treatments. Accumulating evidence points to efficacy of alpha7 nicotinic receptor (nAChR) agonists for cognitive deficits in schizophrenia but their activity against positive symptoms is thought to be minimal. The present study examined potential pro-cognitive and antipsychotic activity of the novel selective alpha7 nAChR partial agonist SSR180711 using the latent inhibition (LI) model. LI is the reduced efficacy of a previously non-reinforced stimulus to gain behavioral control when paired with reinforcement, compared with a novel stimulus. Here, no-drug controls displayed LI if non-reinforced pre-exposure to a tone was followed by weak but not strong conditioning (2 vs 5 tone-shock pairings). MK801 (0.05 mg/kg, i.p.) -treated rats as well as rats neonatally treated with nitric oxide synthase inhibitor L-NoArg (10 mg/kg, s.c.) on postnatal days 4-5, persisted in displaying LI with strong conditioning, whereas amphetamine (1 mg/kg) -treated rats failed to show LI with weak conditioning. SSR180711 (0.3, 1, 3 mg/kg, i.p.) was able to alleviate abnormally persistent LI produced by acute MK801 and neonatal L-NoArg; these models are believed to model cognitive aspects of schizophrenia and activity here was consistent with previous findings with alpha7-nAChR agonists. In addition, unexpectedly, SSR180711 (1, 3 mg/kg, i.p.) potentiated LI with strong conditioning in no-drug controls and reversed amphetamine-induced LI disruption, two effects considered predictive of activity against positive symptoms of schizophrenia. These findings suggest that SSR180711 may be beneficial not only for the treatment of cognitive symptoms in schizophrenia, as reported multiple times previously, but also positive symptoms.

Topics: Acoustic Stimulation; alpha7 Nicotinic Acetylcholine Receptor; Analysis of Variance; Animals; Animals, Newborn; Behavior, Animal; Bridged Bicyclo Compounds, Heterocyclic; Cognition Disorders; Conditioning, Psychological; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Male; Neural Inhibition; Neuroprotective Agents; Nicotinic Agonists; Nitroarginine; Rats; Rats, Wistar; Receptors, Nicotinic; Reinforcement, Psychology; Schizophrenia

The role of SK(Ca) and IK(Ca) channels in myogenic tone and endothelium-derived hyperpolarizing factor (EDHF) responsiveness was investigated under control conditions and after ischemia and reperfusion in parenchymal arterioles (PA) versus middle cerebral arteries (MCA).. MCA and PA were dissected from male Wistar rats that were ischemic for 1 hour with 24 hours of reperfusion (n=12) or sham controls (n=12). Basal tone and reactivity to apamin (300 nmol/L), TRAM-34 (1.0 micromol/L), and nitro-L-arginine (0.1 mmol/L) were compared in PA and MCA pressurized to 40 mm Hg and 75 mm Hg, respectively. SK(Ca) and IK(Ca) channel mRNA expression was measured using real-time PCR.. PA developed greater basal tone than MCA (42+/-4% versus 19+/-3%; P<0.01). Addition of apamin and TRAM-34 increased tone of PA by 25+/-3% and 16+/-2%, respectively, whereas MCA had no response to either inhibitor. After ischemia and reperfusion, the response to nitric oxide synthase inhibition (NOS) was diminished in PA, whereas EDHF responsiveness was preserved. In addition, stimulated EDHF dilation was partially reversed by apamin and completely reversed by TRAM-34 in both control and ischemic PA. SK(Ca) and IK(Ca) channel mRNA expression was similar in PA and MCA and not altered by ischemia and reperfusion. However, IK(Ca) channel mRNA expression was 4- to 5-fold greater than SK(Ca) channels.. It appears that SK(Ca) and IK(Ca) channel activity diminishes basal tone of PA, but not MCA. The preservation of EDHF responsiveness of PA after ischemia and reperfusion suggests an important role for this vasodilator under conditions when NOS is inhibited.

Topics: Animals; Apamin; Arterioles; Biological Factors; Brain Ischemia; Calcimycin; Disease Models, Animal; Enzyme Inhibitors; Intermediate-Conductance Calcium-Activated Potassium Channels; Ionophores; Male; Middle Cerebral Artery; Nitric Oxide; Nitroarginine; Pyrazoles; Rats; Rats, Wistar; Reperfusion Injury; RNA, Messenger; Small-Conductance Calcium-Activated Potassium Channels; Vasodilation

Endothelin (ET)-1 is a likely candidate for a key role in diabetic vascular complications. However, no abnormalities in the vascular responsiveness to ET-1 have been identified in the chronic stage of type 2 diabetes. Our goal was to look for abnormalities in the roles played by ET receptors (ET(A) and ET(B)) in the mesenteric artery of the type 2 diabetic Goto-Kakizaki (GK) rat and to identify the molecular mechanisms involved. Using mesenteric arteries from later-stage (32-38 wk old) individuals, we compared the ET-1-induced contraction and the relaxation induced by the selective ET(B) receptor agonist IRL1620 between GK rats and control Wistar rats. Mesenteric artery ERK activity and the protein expressions for ET receptors and MEK were also measured. In GK rats (vs. age-matched Wistar rats), we found as follows. 1) The ET-1-induced contraction was greater and was attenuated by BQ-123 (ET(A) antagonist) but not by BQ-788 (ET(B) antagonist). In the controls, BQ-788 augmented this contraction. 2) Both the relaxation and nitric oxide (NO) production induced by IRL1620 were reduced. 3) ET-1-induced contraction was enhanced by N(G)-nitro-l-arginine (l-NNA; NO synthase inhibitor) but suppressed by sodium nitroprusside (NO donor). 4) The enhanced ET-1-induced contraction was reduced by MEK/ERK pathway inhibitors (PD-98059 or U0126). 5) ET-1-stimulated ERK activation was increased, as were the ET(A) and MEK1/2 protein expressions. 6) Mesenteric ET-1 content was increased. These results suggest that upregulation of ET(A), a defect in ET(B)-mediated NO signaling, and activation of the MEK/ERK pathway together represent a likely mechanism mediating the hyperreactivity to ET-1 examined in this study.

Topics: Angiotensin II; Animals; Arginine Vasopressin; Butadienes; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Disease Models, Animal; Disease Progression; Dose-Response Relationship, Drug; Endothelin-1; Endothelins; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Male; MAP Kinase Kinase Kinases; Mesenteric Arteries; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitriles; Nitroarginine; Nitroprusside; Oligopeptides; Peptide Fragments; Peptides, Cyclic; Piperidines; Rats; Rats, Wistar; Receptor, Endothelin A; Receptor, Endothelin B; Signal Transduction; Vasoconstriction; Vasodilation

Chronic L-DOPA pharmacotherapy in Parkinson's disease is often accompanied by the development of abnormal and excessive movements known as L-DOPA-induced dyskinesia. Rats with 6-hydroxydopamine lesion of dopaminergic neurons chronically treated with L-DOPA develop a rodent analog of this dyskinesia characterized by severe axial, limb, locomotor and orofacial abnormal involuntary movements. While the mechanisms by which these effects occur are not clear, they may involve the nitric oxide system. In the present study we investigate if nitric oxide synthase inhibitors can prevent dyskinesias induced by repeated administration of L-DOPA in rats with unilateral 6-hydroxydopamine lesion. Chronic L-DOPA (high fixed dose, 100 mg/kg; low escalating dose, 10-30 mg/kg) treatment induced progressive dyskinesia changes. Two nitric oxide synthase inhibitors, 7-nitroindazole (1-30 mg/kg) and NG-nitro-L-arginine (50 mg/kg), given 30 min before L-DOPA, attenuate dyskinesia. 7-Nitroindazolee also improved motor performance of these animals in the rota-rod test. These results suggest the possibility that nitric oxide synthase inhibitors may be useful to treat L-DOPA-induced dyskinesia.

Topics: Animals; Antiparkinson Agents; Corpus Striatum; Disease Models, Animal; Dyskinesia, Drug-Induced; Enzyme Inhibitors; Indazoles; Levodopa; Male; Motor Activity; Nitric Oxide Synthase; Nitroarginine; Oxidopamine; Parkinson Disease; Rats; Rats, Wistar; Substantia Nigra

The aim of this study was to investigate the role of nitric oxide in mesenteric ischemia, organ injury and survival in zymosan-induced multiple organ dysfunction syndrome (MODS) by using the nonselective nitric oxide synthase inhibitor L-N(G)-nitroarginine (L-NNA).. Swiss albino mice (20-40 g) were used in the study. The animals were randomly divided into four groups. The first group was treated intraperitoneally with saline and served as the sham group for L-NNA. The second group was treated with zymosan (500 mg/kg). The mice in the third and fourth group received L-NNA (20 mg/kg), 1 and 6 h after saline or zymosan administration. Six hours after the administration of zymosan, animals were used for mesenteric arterial blood flow (MABF) measurements and then sacrificed for biochemical and histopathological analyses at the 18th hour.. In zymosan-treated animals, MABF was significantly lower than that of solvent saline-treated controls (controls: 4.7 +/- 0.8 ml.min(-1); zymosan: 1.7 +/- 0.7 ml.min(-1), p < 0.05). L-NNA did not prevent zymosan-induced MABF decrease (controls: 4.5 +/- 0.8 ml.min(-1); zymosan: 2.5 +/- 1.4 ml.min(-1), p <0.05). Also treatment with L-NNA has no beneficial effect on survival and organ injury in zymosan-induced MODS.. In this study, inhibition of both inducible and constitutive nitric oxide synthase by L-NNA did not abolish the harmful effects of zymosan. L-NNA remains an agent without any therapeutic potential in this acute experimental model of MODS.

Topics: Animals; Disease Models, Animal; Enzyme Inhibitors; Kidney; Male; Mice; Multiple Organ Failure; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Pancreas; Splanchnic Circulation; Zymosan

Hyperhomocysteinaemia is considered to be an independent risk factor in atherosclerosis. In the present article, we observed the effect of nitric oxide modulators on cardiovascular risk factors in mild hyperhomocysteinaemic rats. A rat model of mild hyperhomocysteinaemia was established by administering methionine (1 g/kg body weight, orally) for 4 weeks. The other groups were concomitantly treated with sodium nitroprusside (SNP) and N(omega)-nitro-l-arginine (LNNA) during the induction of hyperhomocysteinaemia. Lipid profile, total antioxidant capacity and the level of homocysteine and NO(x) (nitrates and nitrites) was examined in serum at 0 and 4 weeks. Activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the mRNA level of caveolin, P2 receptors and cardiovascular risk factors were also analysed. Stimulated lipid profile of rats by the treatment of methionine (1 g/kg body weight) reduced significantly by the treatment of SNP with methionine. LNNA increased the level of cholesterol in aorta (P < 0.05 versus group II). SNP significantly suppressed the activity of HMG-CoA reductase. The mRNA levels of caveolin (P < 0.05), P2X (P < 0.05) and P2Y (P < 0.05) showed a significant decrease in rats administered with SNP. LNNA showed significant induction in the expression of caveolin (P < 0.01) and P2Y (P < 0.01) expression. The level of P2X showed no remarkable change in animals treated with LNNA and methionine both. These data conclude that nitric oxide modulators modulate the effect of hyperhomocysteinaemia on the other cardiovascular risk factors and confirm the finding that nitric oxide plays an important role in homocysteine-induced cardiovascular diseases.

Topics: Acyl Coenzyme A; Animals; Aorta, Thoracic; C-Reactive Protein; Cardiovascular Diseases; Caveolin 2; Disease Models, Animal; Hyperhomocysteinemia; Leukotrienes; Lipid Metabolism; Liver; Male; Methionine; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Nitroprusside; Oxidative Stress; Rats; Rats, Wistar; Receptors, Purinergic P2; Resistin; Risk Factors

Endogenous nitric oxide (NO) mediates pulmonary vasodilatation at birth, but inhaled NO fails to reduce pulmonary vascular resistance (PVR) in newborns with congenital diaphragmatic hernia (CDH). This study was designed to investigate the effects of ventilation, and the nature of its endogenous mediator, in fetal lambs with experimental CDH. Investigations at 138 days of gestation showed that ventilation markedly decreased PVR. Inhibition of NO synthesis reduced ventilation-induced pulmonary vasodilatation in vivo and increased in vitro isometric tension of vascular rings. Ventilation therefore reduces PVR at birth in lambs with CDH, and endogenous NO seems to contribute to this reduction.

Topics: Animals; Disease Models, Animal; Electric Stimulation; Enzyme Inhibitors; Gestational Age; Hemodynamics; Hernia, Diaphragmatic; Hernias, Diaphragmatic, Congenital; Lung; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Pulmonary Circulation; Respiration, Artificial; Sheep; Vascular Resistance; Vasodilation

The hypothesis of the present study was that molecular mechanisms differ markedly when mediating ischemic preconditioning induced by repetitive episodes of ischemia versus classic first- or second-window preconditioning.. To test this, chronically instrumented conscious pigs were subjected to either repetitive coronary stenosis (RCS) or a traditional protocol of second-window ischemic preconditioning (SWIPC). Lethal ischemia, induced by 60 minutes of coronary artery occlusion followed by reperfusion, resulted in an infarct size/area at risk of 6+/-3% after RCS and 16+/-3% after SWIPC (both groups P<0.05, less than shams 42+/-4%). Two molecular signatures of SWIPC, the increased expression of the inducible isoform of nitric oxide synthase and the translocation of protein kinase Cepsilon to the plasma membrane, were observed with SWIPC but not with RCS. Confirming this, pretreatment with a nitric oxide synthase inhibitor prevented the protection conferred by SWIPC but not by RCS. Microarray analysis revealed a qualitatively different genomic profile of cardioprotection between ischemic preconditioning induced by RCS and that induced by SWIPC. The number of genes significantly regulated was greater in RCS (5739) than in SWIPC (2394) animals. Of the 5739 genes regulated in RCS, only 31% were also regulated in SWIPC. Broad categories of genes induced by RCS but not SWIPC included those involved in autophagy, endoplasmic reticulum stress, and mitochondrial oxidative metabolism. The upregulation of these pathways was confirmed by Western blotting.. RCS induces cardioprotection against lethal myocardial ischemia that is at least as powerful as traditional ischemic preconditioning but is mediated through radically different mechanisms.

Topics: Animals; Consciousness; Coronary Circulation; Coronary Stenosis; Disease Models, Animal; Enzyme Inhibitors; Female; Ischemic Preconditioning, Myocardial; Myocardial Reperfusion Injury; Myocardial Stunning; Nitric Oxide; Nitric Oxide Synthase Type II; Nitroarginine; Oligonucleotide Array Sequence Analysis; Protein Kinase C-epsilon; Recurrence; Swine

The aim of the study was to assess the rat pial microvessel alterations due to transient bilateral common carotid artery occlusion (BCCAO) and to investigate the mechanism of 10% hypertonic glycerol neuroprotection. Our suggestion was that 10% glycerol solution infusion could dilate pial arterioles through nitric oxide release and/or stimulation of ATP-sensitive potassium (K(ATP)) channels. Therefore, we studied the effects of hypertonic glycerol after inhibition of nitric oxide synthase, with N(G)-nitro-L-arginine-methyl ester or N(G)-nitro-L-arginine, or K(ATP) channels with glibenclamide.. Pial microcirculation of male Wistar rats was visualized by a fluorescent microscopy technique through an open cranial window, using fluorescein isothiocyanate bound to dextran (molecular weight 70 kDa). BCCAO was induced for 30 min and reperfusion lasted 60 min. The arterioles were classified according to the Strahler ordering scheme. Permeability increase was quantified by normalized grey levels (NGL). Leucocytes were stained with rhodamine 6G. Perfused capillary length and capillary red blood cell (RBC) velocity were measured by computer-assisted methods.. The arterioles were assigned 5 orders of branchings, from order 1 (diameter 16.0 +/- 2.5 microm) to order 5 (62.0 +/- 5.0 microm). BCCAO caused inhomogenous changes in diameter of arterioles and leakage of fluorescent dextran, that was further enhanced by reperfusion (0.45 +/- 0.05 NGL, p < 0.01). Adhesion of leukocytes to venules was marked and capillary perfusion was reduced by 39.2 +/- 6.0% of baseline as well as capillary RBC velocity. 10% glycerol solution caused an increase in diameter of all arterioles within 25 +/- 2 min of administration (by 20 +/- 5% in order 4, 25 +/- 4% in order 3 and 18 +/- 3% in order 2; p < 0.01). Leakage (0.19 +/- 0.03 NGL, p < 0.01), leukocyte adhesion (2.0 +/- 1.0/100 microm of venular length, p < 0.01) and capillary occlusion (reduction by 13.0 +/- 5.5% of baseline) were prevented compared with controls. Capillary RBC velocity increased compared with controls. N(G)-nitro-L-arginine-methyl ester or N(G)-nitro-L-arginine infused prior to glycerol caused vasoconstriction and reduced the protective effects of hypertonic glycerol on permeability increase. The number of adherent leukocytes and perfused capillary length decreased, while capillary RBC velocity was higher than baseline. Glibenclamide prior to 10% glycerol solution blunted glycerol-induced vasodilatation, but did not affect protection by hypertonic glycerol on blood-brain barrier disruption, leukocyte adhesion and capillary perfusion, preserving high capillary RBC velocity. Papaverine (20 mg/kg body weight) induced an increase in arteriolar diameter, enhancing interstitial edema; adhesion of leukocytes was marked as well as capillary occlusion, while capillary RBC velocity increased.. 10% glycerol solution was able to prevent microvascular alterations due to BCCAO protecting cerebral tissue. The effects appear to be due to hyperosmolality causing stimulation of K(ATP) channels, increase in vessel wall shear stress and release of nitric oxide.

Topics: Animals; Blood Flow Velocity; Capillary Permeability; Carotid Artery, Common; Carotid Stenosis; Cell Adhesion; Cerebrovascular Circulation; Chemotaxis, Leukocyte; Disease Models, Animal; Glyburide; Glycerol; Hypertonic Solutions; Infusions, Intravenous; KATP Channels; Ligation; Male; Microcirculation; Microscopy, Fluorescence; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Papaverine; Pia Mater; Potassium Channel Blockers; Rats; Rats, Wistar; Regional Blood Flow; Vasodilation; Vasodilator Agents

1. The present study evaluated the effect of diabetes, hypercholesterolaemia and their combination on the contribution of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) to relaxation of rat isolated aortic rings and the potential contribution of oxidant stress to the disturbance of endothelial function. 2. Thoracic aortic rings from control, diabetic, hypercholesterolaemic and diabetic plus hypercholesterolaemic rats were suspended in organ baths for tension recording. Generation of superoxide by the aorta was measured using lucigenin-enhanced chemiluminescence. 3. The maximal response to acetylcholine (ACh) was significantly reduced in diabetic or hypercholesterolaemic rats compared with control rats. In rats with diabetes plus hypercholesterolaemia, both the sensitivity and maximal response to ACh was impaired. In control rats, the response to ACh was abolished by the NO synthase inhibitor N(G)-nitro-L-arginine (L-NNA) or inhibition of soluble guanylate cyclase with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). In contrast, in rats with diabetes, hypercholesterolaemia or both, relaxation to ACh was resistant to inhibition by L-NNA or ODQ, but abolished by additional inhibition of K(Ca) channels with charybdotoxin plus apamin. 4. The generation of superoxide was not significantly enhanced in aortic rings from either diabetic or hypercholesterolaemic rats, but was significantly increased in aortic rings from rats with diabetes plus hypercholesterolaemia. 5. These results suggest that when diabetes and hypercholesterolaemia impair endothelium-dependent relaxation, due to a diminished contribution from NO, a compensatory contribution of EDHF to endothelium-dependent relaxation of the aorta is revealed. The attenuation of NO-mediated relaxation, at least in the presence of both diabetes and hypercholesterolaemia, is associated with enhanced superoxide generation.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Apamin; Biological Factors; Blood Glucose; Body Weight; Charybdotoxin; Cholesterol; Cyclooxygenase Inhibitors; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Hypercholesterolemia; Indomethacin; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Oxadiazoles; Oxidative Stress; Potassium Channel Blockers; Potassium Channels, Calcium-Activated; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Superoxides; Vasodilation; Vasodilator Agents

Cardiovascular disease and type 2 diabetes mellitus are associated with low plasma concentration of adiponectin. The aim of this study was to investigate whether adiponectin exerts cardioprotective effects during myocardial ischaemia-reperfusion and whether this effect is related to the production of nitric oxide (NO).. Isolated rat hearts were subjected to 30 min of either global or local ischaemia followed by 60 min of reperfusion. The hearts received vehicle, adiponectin (3 microg/mL), the NO-synthase inhibitor nitro-l-arginine (L-NNA) (0.1 mM), or a combination of adiponectin and L-NNA at the onset of ischaemia. Haemodynamics, infarct size, and expression of endothelial NO-synthase (eNOS), AMP-activated protein kinase (AMPK), and Akt were determined. Adiponectin significantly increased left ventricular function and coronary flow during reperfusion in comparison with the vehicle group. Co-administration of L-NNA abrogated the improvement in myocardial function induced by adiponectin. Infarct size following local ischaemia-reperfusion was 40 +/- 6% of the area at risk in the vehicle group. Adiponectin reduced infarct size to 19 +/- 2% (P < 0.01). L-NNA did not affect infarct size per se but abolished the protective effect of adiponectin (infarct size 40 +/- 5%). Phosphorylation of eNOS Ser1177, AMPK Thr172, and Akt Ser 473 was increased in the adiponectin group (P < 0.05).. Adiponectin protects from myocardial contractile dysfunction and limits infarct size following ischaemia and reperfusion by a mechanism involving activation of AMPK and production of NO.

Topics: Adiponectin; AMP-Activated Protein Kinases; Animals; Blotting, Western; Coronary Circulation; Disease Models, Animal; Enzyme Inhibitors; Hemodynamics; Humans; Male; Multienzyme Complexes; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Phosphorylation; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Signal Transduction; Time Factors; Ventricular Function, Left

Mutations in genes encoding members of the GDNF and endothelin-3 (Et-3) signaling pathways can cause Hirschsprung's disease, a congenital condition associated with an absence of enteric neurons in the distal gut. GDNF signals through Ret, a receptor tyrosine kinase, and Et-3 signals through endothelin receptor B (Ednrb). The effects of Gdnf, Ret, and ET-3 haploinsufficiency and a null mutation in ET-3 on spontaneous motility patterns in adult and developing mice were investigated. Video recordings were used to construct spatiotemporal maps of spontaneous contractile patterns in colon from postnatal and adult mice in vitro. In Ret(+/-) and ET-3(+/-) mice, which have normal numbers of enteric neurons, colonic migrating motor complexes (CMMCs) displayed similar properties under control conditions and following inhibition of nitric oxide synthase (NOS) activity to wild-type mice. In the colon of Gdnf(+/-) mice and in the ganglionic region of ET-3(-/-) mice, there was a 50-60% reduction in myenteric neuron number. In Gdnf(+/-) mice, CMMCs were present, but abnormal, and the proportion of myenteric neurons containing NOS was not different from that of wild-type mice. In the ganglionic region of postnatal ET-3(-/-) mice, CMMCs were absent, and the proportion of myenteric neurons containing NOS was over 100% higher than in wild-type mice. Thus impairments in spontaneous motility patterns in the colon of Gdnf(+/-) mice and in the ganglionic region of ET-3(-/-) mice are correlated with a reduction in myenteric neuron density.

Topics: Age Factors; Aging; Animals; Animals, Newborn; Colon; Disease Models, Animal; Endothelin-3; Enteric Nervous System; Enzyme Inhibitors; Gastrointestinal Motility; Glial Cell Line-Derived Neurotrophic Factor; Granisetron; Hirschsprung Disease; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Myoelectric Complex, Migrating; Nitric Oxide Synthase; Nitroarginine; Proto-Oncogene Proteins c-ret; Receptors, Serotonin, 5-HT3; Serotonin 5-HT3 Receptor Antagonists; Serotonin Antagonists; Time Factors; Video Recording

Morphine can inhibit inflammatory edema in experimental animals. The mechanisms and sites by which opioids exert this effect are still under debate. Since the spinal level is a site for modulation of the neurogenic component of inflammation, we investigated the effect of intrathecal (i.t.) administration of morphine, and the involvement of spinal nitric oxide (NO)/cyclic-guanosine monophosphate-GMP pathway in carrageenan (CG)-induced paw edema.. Male Wistar rats received i.t. injections of drugs (20 microL) 30 min before paw stimulation with CG (150 microg). Edema was measured as paw volume increase (mL), and neutrophil migration was evaluated indirectly by myeloperoxidase (MPO) assay.. Morphine (37, 75, and 150 nmol) inhibited inflammatory edema, but had no effect on MPO activity. Coinjection with naloxone (64 nmol) reversed the effect of morphine. The corticosteroid synthesis inhibitor, aminoglutethimide (50 mg/kg, v.o.), administered 90 min before morphine injection did not modify its antiedematogenic effect. Low doses of the NO synthase inhibitor, N(omega)-nitro-L-arginine (L-NNA; 10 and 30 pmol) increased, while higher doses (3 and 30 nmol) inhibited edema. The guanylate cyclase inhibitor 1H-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 21 and 42 nmol) increased, while the phosphodiesterase type 5 inhibitor sildenafil (0.15 and 1.5 nmol) inhibited paw edema. Coadministration of a subeffective dose of L-NNA (3 pmol) or ODQ (10 nmol) with morphine prevented its antiedematogenic effect, but sildenafil (0.15 nmol) rendered a subeffective dose of morphine effective (18 nmol). ODQ also prevented the antiedematogenic effect of the NO donor S-nitroso-N-acetyl-penicilamine.. These results support the idea that morphine can act on opioid receptors at the spinal level to produce antiedematogenic, and that the NO/cGMP pathway seems to be an important mediator in this effect.

Topics: Analgesics, Opioid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Carrageenan; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Edema; Enzyme Inhibitors; Guanylate Cyclase; Inflammation; Injections, Spinal; Male; Morphine; Naloxone; Narcotic Antagonists; Neutrophil Infiltration; Neutrophils; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Oxadiazoles; Peroxidase; Phosphodiesterase Inhibitors; Piperazines; Purines; Quinoxalines; Rats; Rats, Wistar; S-Nitroso-N-Acetylpenicillamine; Signal Transduction; Sildenafil Citrate; Spinal Cord; Sulfones; Time Factors

Previous investigations have indicated that angiotensin II (Ang II)-induced hypertension and endothelial dysfunction are prevented by intake of red wine polyphenols (RWPs). Ang II has also been shown to increase the expression of VEGF and MMP-2, two major pro-inflammatory factors, in vascular diseases. Therefore, the aim of the present study was to determine whether intake of RWPs is able to prevent these effects in rats and, if so, to characterize the underlying mechanism.. VEGF and endothelial NO synthase (eNOS) expression was assessed by immunofluorescence and Western blotting, MMP-2 activity by zymography, and reactive oxygen species (ROS) formation by dihydroethidine.. Ang II increased VEGF expression and MMP-2 activity in the aortic wall. Ang II-induced MMP-2 activation is inhibited by N(G)-nitro-L-arginine and MnTMPyP. Ang II increased the expression of eNOS, the formation of ROS and the nitration of proteins. The stimulatory effects of Ang II on these factors are prevented by RWPs intake.. Infusion of Ang II induced vascular expression of VEGF and peroxynitrite-dependent activation of MMP-2, with both effects being prevented by RWPs intake. Thus, prevention of VEGF and MMP-2 expression might be involved in the protective effect of red wine on coronary heart diseases.

Topics: Angiotensin II; Animals; Antihypertensive Agents; Aorta; Blood Pressure; Blotting, Western; Disease Models, Animal; Enzyme Inhibitors; Flavonoids; Fluorescent Antibody Technique; Hypertension; Male; Matrix Metalloproteinase 2; Metalloporphyrins; Nitric Oxide; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Peroxynitrous Acid; Phenols; Polyphenols; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Time Factors; Up-Regulation; Vascular Endothelial Growth Factor A; Wine

Although, there are some evidences on the contribution of increased sympathoadrenergic activity on long-term nitric oxide synthase (NOS) inhibition induced hypertension, the contribution of sympathetic activity to the development of this model of hypertension are not sufficiently studied. The aim of the present study is to investigate the effects of clonidine on blood pressure and vascular alpha-adrenergic receptors in the long-term N (omega)-nitro-L-arginine (L-NNA) treated rats.. Sixty two Wistar rats were randomly divided into 8 groups. All groups were administrated L-NNA and/or clonidine in two different concentrations for ten days. L-NNA was administrated in concentrations of 15 and 45 mg/100ml to L-NNA15 and L-NNA45 groups, respectively. Clonidine was also administrated in concentrations of 150 and 225 microg/100ml to KLO150 and KLO225 groups, respectively. Blood pressure and heart rates were measured with tail-cuff method and plasma NOx levels with spectrophotometer. The a-adrenoreceptors responses were evaluated in thoracic aorta rings in "in vitro" conditions.. Clonidine prevented the L-NNA induced hypertension dose-dependently, but did not effect the heart rates decreased by L-NNA. The heart rates and blood pressure of normotensive rats were not changed by clonidine alone. Plasma NOx levels increased in L-NNA15 group (0.62+/-0.11 micromol/L, p=0.003) but did not change in other groups. The sensitivity of aorta to phenylephrine (-7.33+/-0.11 micromol/L, p=0.001) and clonidine (-7.60+/-0.27 micromol/L, p=0.003) in L-NNA45 group and phenylephrine (-6.94+/-0.13 micromol/L, p=0.002) in L-NNA15 group increased. The sensitivity of aorta to phenylephrine (7.93+/-0.16 micromol/L, p=0.001) in KLO225 group and to clonidine (-7.20+/-0.10 micromol/L, p=0.009) in KLO150 group increased.. This study supports the idea suggesting that symphathetic nervous system activation is partly responsible for the development of the long-term NOS inhibition induced hypertension. In conclusion, it was shown for the first time that clonidine prevents the development of long-term NOS inhibition induced hypertension dose-dependently.

Topics: Animals; Antihypertensive Agents; Aorta, Thoracic; Blood Pressure; Clonidine; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Heart Rate; Hypertension; Male; Nitroarginine; Random Allocation; Rats; Rats, Wistar

Controversy exists as to whether platelet-activating factor (PAF), a potent phospholipid mediator of inflammation, can actually protect the heart from postischemic injury. To determine whether endogenous activation of the PAF receptor is cardioprotective, we examined postischemic functional recovery in isolated hearts from wild-type and PAF receptor-knockout mice. Postischemic function was reduced in hearts with targeted deletion of the PAF receptor and in wild-type hearts treated with a PAF receptor antagonist. Furthermore, perfusion with picomolar concentrations of PAF improved postischemic function in hearts from wild-type mice. To elucidate the mechanism of a PAF-mediated cardioprotective effect, we employed a model of intracellular Ca2+ overload and loss of function in nonischemic ventricular myocytes. We found that PAF receptor activation attenuates the time-dependent loss of shortening and increases in intracellular Ca2+ transients in Ca2+ -overloaded myocytes. These protective effects of PAF depend on nitric oxide, but not activation of cGMP. In addition, we found that reversible S-nitrosylation of myocardial proteins must occur in order for PAF to moderate Ca2+ overload and loss of myocyte function. Thus our data are consistent with the hypothesis that low-level PAF receptor activation initiates nitric oxide-induced S-nitrosylation of Ca2+ -handling proteins, e.g., L-type Ca2+ channels, to attenuate Ca2+ overload during ischemia-reperfusion in the heart. Since inhibition of the PAF protective pathway reduces myocardial postischemic function, our results raise concern that clinical therapies for inflammatory diseases that lead to complete blockade of the PAF receptor may eliminate a significant, endogenous cardioprotective pathway.

Topics: Animals; Calcium; Calcium Signaling; Cell Shape; Cyclic GMP; Disease Models, Animal; Enzyme Inhibitors; Female; Ginkgolides; Lactones; Male; Mice; Mice, Inbred C57BL; Muscle Proteins; Myocardial Contraction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Platelet Activating Factor; Rats; Rats, Wistar; Time Factors; Ventricular Function, Left

The involvement of matrix metalloproteinases (MMPs) in ischemic tissue damage and remodeling has been reported by many investigators. Our study was designed to investigate the involvement of MMPs and of tissue inhibitors of metalloproteinases (TIMPs) in rat retinal ischemic injury, the effect of nitric oxide synthase (NOS) inhibitors on MMPs' activity in this model and whether minocycline (an MMP inhibitor) is protective in retinal ischemia.. Ninety-four rats were used in the study. Ischemia was induced by 90 min elevation of intraocular pressure. MMPs' activities and the effect of NOS inhibitors [aminoguanidine (AG) or N-nitro-L-arginine (NNA)] and minocycline on MMPs' activities were assessed by zymography and TIMPs expression by Western analysis. Morphological damage was quantified by morphometry of hematoxylin and eosin-stained retinal sections.. Retinal extracts exhibited activities of proMMP-9 and proMMP-2. The activity of proMMP-9 increased immediately post ischemia (PI) and peaked to 4.6 times that of normal untreated controls in ischemic retinas and to 2.6 times that of controls in retinas of fellow sham-treated eyes at 24 h PI. The relative amount of TIMP-1 increased to 1.9-fold following ischemia and 2.5-fold in fellow sham-treated eyes at 24 h PI. ProMMP-2 activity increased more than two-fold immediately, at 24 h and at 48 h PI in ischemic retinas, and insignificantly in fellow sham-treated eyes. Treatment with 25 mg/kg AG or NNA caused a non-significant increase in proMMP-9 activity at 24 h PI (3.7- and 2.9-fold, respectively, p>0.6). There was no effect of AG or NNA on the activity of proMMP-2. Minocycline significantly attenuated the retinal ischemic damage, primarily by partially preserving ganglion cells and the inner plexiform layer. Minocyline (0.5 mg/ml or 5 mg/ml) inhibited MMPs' activities in ischemic retinal extracts in vitro.. MMPs participated in morphological ischemic damage to rat retina. Treatment with minocycline dramatically attenuated damage to the retina.

Topics: Animals; Blotting, Western; Disease Models, Animal; Enzyme Inhibitors; Guanidines; Ischemia; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Matrix Metalloproteinase Inhibitors; Minocycline; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Retinal Diseases; Retinal Vessels; Tissue Inhibitor of Metalloproteinase-1

We have previously shown that direct vagus nerve stimulation (VNS) reduces the slope of action potential duration (APD) restitution while simultaneously protecting the heart against induction of ventricular fibrillation (VF) in the absence of any sympathetic activity or tone. In the current study we have examined the role of nitric oxide (NO) in the effect of VNS. Monophasic action potentials were recorded from a left ventricular epicardial site on innervated, isolated rabbit hearts (n = 7). Standard restitution, effective refractory period (ERP) and VF threshold (VFT) were measured at baseline and during VNS in the presence of the NO synthase inhibitor N(G)-nitro-L-arginine (L-NA, 200 microm) and during reversing NO blockade with L-arginine (L-Arg, 1 mm). Data represent the mean +/- S.E.M. The restitution curve was shifted upwards and became less steep with VNS when compared to baseline. L-NA blocked the effect of VNS whereas L-Arg restored the effect of VNS. The maximum slope of restitution was reduced from 1.17 +/- 0.14 to 0.60 +/- 0.09 (50 +/- 5%, P < 0.0001) during control, from 0.98 +/- 0.14 to 0.93 +/- 0.12 (2 +/- 10%, P = NS) in the presence of L-NA and from 1.16 +/- 0.17 to 0.50 +/- 0.10 (41 +/- 9%, P = 0.003) with L-Arg plus L-NA. ERP was increased by VNS in control from 119 +/- 6 ms to 130 +/- 6 ms (10 +/- 5%, P = 0.045) and this increase was not affected by L-NA (120 +/- 4 to 133 +/- 4 ms, 11 +/- 3%, P = 0.0019) or L-Arg with L-NA (114 +/- 4 to 123 +/- 4 ms, 8 +/- 2%, P = 0.006). VFT was increased from 3.0 +/- 0.3 to 5.8 +/- 0.5 mA (98 +/- 12%, P = 0.0017) in control, 3.4 +/- 0.4 to 3.8 +/- 0.5 mA (13 +/- 12%, P = 0.6) during perfusion with L-NA and 2.5 +/- 0.4 to 6.0 +/- 0.7 mA (175 +/- 50%, P = 0.0017) during perfusion with L-Arg plus L-NA. Direct VNS increased VFT and flattened the slope of APD restitution curve in this isolated rabbit heart preparation with intact autonomic nerves. These effects were blocked using L-NA and reversed by replenishing the substrate for NO production with L-Arg. This is the first study to demonstrate that NO plays an important role in the anti-fibrillatory effect of VNS on the rabbit ventricle, possibly via effects on APD restitution.

Topics: Action Potentials; Animals; Arginine; Autonomic Nervous System; Cardiac Pacing, Artificial; Disease Models, Animal; Electric Stimulation; Enzyme Inhibitors; Heart; Heart Rate; Heart Ventricles; In Vitro Techniques; Male; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Perfusion; Rabbits; Time Factors; Vagus Nerve; Ventricular Fibrillation; Ventricular Function

Colitis induced by Trichinella spiralis in rat induces alterations in the spontaneous motor pattern displayed by circular colonic muscle [Auli, M., Fernandez, E., 2005. Characterization of functional and morphological changes in a rat model of colitis induced by T. spiralis. Digestive Diseases and Sciences 50(8), 1432-1443]. We examined the temporal relationship between the severity of inflammation and the altered contractility of the underlying circular muscle as well as the role of NANC inhibitory pathways in the disruption of the motility pattern. Colitis was induced by intrarectal administration of T. spiralis larvae. Responses to acetylcholine (ACh) and increased extracellular potassium as well as the effect of tetrodotoxin (TTX, 1 microM), N-nitro-l-arginine (L-NOARG, 1 mM) and apamin (1 microM) were determined in vitro in the organ bath with circular muscle strips from sham-infected and infected rats at days 2-30 postinfection (PI). Microelectrode recordings were performed to study the putative changes in electrical activity of colonic smooth muscle cells. Responses to ACh and KCl were decreased at all days PI compared to sham. Intracellular calcium depletion had a greater inhibitory effect in inflamed tissue (6-14 PI). The effect of TTX, L-NOARG and apamin on the spontaneous contractions was found to be altered in all infected rats, i.e. their effects were transient and milder. Inflamed tissue showed lower resting membrane potential and a decreased duration of inhibitory junction potentials induced by electrical stimulation. These data suggest that the decreased contractility of colonic circular smooth muscle induced by the intrarectal T. spiralis infection results from the impairment of the excitation-contraction coupling, from a persistent hyperpolarization of smooth muscle cells and from impaired NANC inhibitory neurotransmission.

Topics: Acetylcholine; Animals; Apamin; Colitis; Disease Models, Animal; Disease Progression; Electric Stimulation; Enteric Nervous System; Gastrointestinal Motility; Inflammation; Intestines; Male; Muscle Contraction; Muscle, Smooth; Nitroarginine; Rats; Rats, Sprague-Dawley; Signal Transduction; Synaptic Transmission; Tetrodotoxin; Time Factors; Trichinella spiralis; Trichinellosis

This study investigated the involvement of the L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway in the antidepressant-like effect of an acute administration of memantine in the forced swimming test (FST) in mice, since this signaling pathway is supposed to play a significant role in depression. The antidepressant-like effect of memantine (3 mg/kg, i.p.) was prevented by pretreatment with L-arginine (750 mg/kg, i.p.) or S-nitroso-N-acetyl-penicillamine (SNAP, 25 microg/site, i.c.v.), but not with d-arginine (750 mg/kg, i.p.).The treatment of mice with NG-nitro-L-arginine (L-NNA, 0.03 and 0.3 mg/kg, i.p.) potentiated the effect of a subeffective dose of memantine (0.3 mg/kg, i.p.) in the FST. Moreover, the pretreatment of mice with (1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one) (ODQ, 30 pmol/site, i.c.v.) produced a synergistic antidepressant-like effect with subeffective doses of memantine (0.3 and 1 mg/kg, i.p.) in the FST. Furthermore, the reduction in the immobility time elicited by memantine (3 mg/kg, i.p.) in the FST was prevented by pretreatment with sildenafil (5 mg/kg, i.p.). Taken together, the results demonstrate that memantine produced an antidepressant-like effect in the FST that seems to be mediated through an interaction with the L-arginine-NO-cGMP pathway.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Arginine; Cyclic GMP; Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Female; Immobility Response, Tonic; Male; Memantine; Mice; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Penicillamine; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swimming

Previously [Histochem J 1997;29:279-286], we found that sympathectomy induced neointima formation in ear but not cerebral arteries of genetically hyperlipidemic rabbits. To clarify the influence of sympathetic nerves in atherosclerosis, and whether their influence involves vascular NO activity, we studied groups of normocholesterolemic intact (NI) and sympathectomized (NS), and hypercholesterolemic intact (HI) and sympathectomized (HS) rabbits (diet/6-hydroxydopamine for 79 days). Segments of basilar (BA) and femoral (FA) arteries were studied histochemically, to evaluate differentiation (anti-desmin, anti-vimentin, anti-h-caldesmon, and nuclear dye), by confocal microscopy, and by in vitro myography. In BAs, staining of NI and NS groups was similar. In hypercholesterolemic groups, a small neointima developed, more frequently in HS segments where smooth muscle cells (SMCs) positive for all antibodies appeared to be migrating into the neointima. In FAs, SMCs stained for the three antibodies in the NI group, but we observed desmin- and h-caldesmon-negative, vimentin-positive cells in some external medial layers of the NS, HI and HS groups, identical to adventitial fibroblasts. Large neointimas of the HS group contained vimentin-positive and largely desmin- and h-caldesmon-negative cells. Relaxation of BA or FA segments to acetylcholine was not decreased by sympathectomy. Sympathectomy increased the contraction of resting FAs to nitro-L-arginine (p = 0.0379). Thus, sympathectomy aggravates the tendency for FA SMCs to migrate and dedifferentiate, increasing atherosclerotic lesions, without decreasing NO activity, but has only minor effects on BAs.

Topics: Acetylcholine; Animals; Atherosclerosis; Basilar Artery; Cell Differentiation; Cell Movement; Cell Proliferation; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Femoral Artery; Hypercholesterolemia; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidopamine; Rabbits; Sympathectomy, Chemical; Tunica Intima; Tunica Media; Vasodilator Agents

Fluid loading is an essential part of cardiovascular resuscitation in septic shock. We hypothesized that fluid administration increases blood flow velocity and thus endothelial shear stress, causing the release of nitric oxide by the vascular endothelium. Because of endothelial dysfunction in sepsis, this mechanism would be less effective in septic animals. Fluid loading may have different effects in septic compared with control animals.. Prospective, randomized, controlled study.. Animal research laboratory.. Male Sprague-Dawley rats.. We tested the involvement of nitric oxide in the fluid-induced cardiovascular response after administration of lipopolysaccharide (5 mg/kg, n = 10) or vehicle (control, n = 10) in rats subsequently randomized after 165 mins to receive L-N(G)-nitroarginine (7.5 mg/kg) or saline (n = 5 in each group). At 180 mins, all animals received hydroxyethyl starch (fluid loading, 15 mL/kg in 15 mins). Reversal of L-N(G)-nitroarginine was studied with an intravenous bolus of L-arginine (300 mg/kg).. Lipopolysaccharide injection induced a hypokinetic shock (low blood pressure: -30% +/- 9%, p < .05), low cardiac output (aortic pulsed-Doppler probe: -20% +/- 8, p < .05), and unchanged systemic conductance, which turned into a hyperkinetic shock by fluid loading. Pretreatment with L-N(G)-nitroarginine totally abolished this fluid loading-induced vasodilation in control rats but only partially in lipopolysaccharide-treated rats, suggesting an altered endothelial response after lipopolysaccharide injection. Maximal aortic blood flow acceleration was used as an index of left ventricular systolic function. The improvement of maximal aortic blood flow acceleration observed during fluid loading in lipopolysaccharide-treated or control animals was blunted by L-N(G)-nitroarginine pretreatment, suggesting the involvement of nitric oxide in the myocardial response to fluid loading.. These results suggest that the endothelium participates in the hemodynamic response to fluid loading in control rats, but less in rats with septic shock, secondary to an altered nitric oxide-dependent vasodilation.

Topics: Animals; Aorta; Blood Flow Velocity; Cardiac Output, Low; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Escherichia coli; Injections, Intravenous; Lipopolysaccharides; Male; Nitric Oxide; Nitroarginine; Prospective Studies; Random Allocation; Rats; Rats, Sprague-Dawley; Resuscitation; Shock, Septic; Vasodilation

Topics: Animals; Disease Models, Animal; Ischemic Preconditioning; Lung; Male; Nitric Oxide Synthase; Nitroarginine; Rabbits; Reperfusion Injury

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

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

Drugs like haloperidol (Hal) that decrease dopamine (DA) neurotransmission in the striatum induce catalepsy in rodents and Parkinson disease-like symptoms in humans. Nitric oxide synthase (NOS) inhibitors interfere with motor activity, disrupting rodent exploratory behavior and inducing catalepsy. Catalepsy induced by NOS inhibitors probably involves striatal DA-mediated neurotransmission. Antioxidants such as ascorbic acid (vitamin C) and alpha-tocopherol (vitamin E) have also been shown to interfere with movement modulation and the DA system.. The objective of the study is to investigate if the antioxidants vitamins C and E would influence the catalepsy produced by Hal and NOS inhibitors.. The effects of the following treatments on catalepsy were examined using the hanging-bar test on male Swiss mice (25-30 g): (1) vitamin C (30-1,000 mg/kg)xHal (1 mg/kg); (2) vitamin C (90-1,000 mg/kg)xN (G)-nitro-L: -arginine (LNOARG, 10 and 40 mg/kg); (3) vitamin C (300 mg/kg)xN (G)-nitro-L: -arginine methylester (LNAME, 20-80 mg/kg); (4) vitamin C (300 mg/kg) x 7-nitroindazole (7NI, 3-50 mg/kg); (5) vitamin C (90 mg/kg i.p.) x LNOARG [40 mg/kg twice a day during 4 days (subchronic treatment)]; (7) vitamin E (3-100 mg/kg) x Hal (1 mg/kg); and (6) vitamin E (3-100 mg/kg) x LNOARG (40 mg/kg).. Vitamin C enhanced the catalepsy produced by NOS inhibitors and Hal. Treatment with vitamin C did not affect tolerance to LNOARG cataleptic effect induced by subchronic treatment. Vitamin E potentiated the catalepsy induced by LNOARG at all doses tested; in contrast, catalepsy induced by Hal was enhanced only by the dose of 100 mg/kg.. Results support an involvement of dopaminergic and nitrergic systems in motor behavior control and provide compelling evidence that combined administration of the antioxidants vitamins C and E with either Hal or NOS inhibitors exacerbates extrapyramidal effects. Further studies are needed to assess possible clinical implications of these findings.

Topics: alpha-Tocopherol; Animals; Ascorbic Acid; Catalepsy; Disease Models, Animal; Dopamine Antagonists; Dose-Response Relationship, Drug; Drug Synergism; Drug Tolerance; Enzyme Inhibitors; Haloperidol; Indazoles; Male; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitroarginine; Time Factors; Vitamins

We have demonstrated previously that the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine (L-NNA) decreases free radical generation and nitrosative injury via peroxynitrite formation after epicardial dc shocks.. Our purpose was to explore the effects of NOS inhibition and NOS donation on cardiopulmonary resuscitation (CPR) success after cardiac arrest of variable duration. We used the non-selective NOS inhibitor L-NNA and the selective neuronal NOS inhibitor ARR-17477, the NOS donor S-nitroso-N-acetylpenicillamine (SNAP) and the vasodilator Enalaprilat, which lowers arterial pressure via a non-NO mechanism.. Part I: 17 pigs undergoing 4 min supported (i.e. with closed-chest compression and ventilation) ventricular fibrillation (VF) were divided into two groups: a no-L-NNA group (n=8) receiving IV saline and an L-NNA group (n=9) receiving IV L-NNA (5 mg/kg) for 8 min before VF was induced. Part II: 35 pigs undergoing 6-8 min VF were randomized to three groups: a no-L-NNA group (n=13) receiving IV saline, an L-NNA group (n=11) receiving IV L-NNA (5 mg/kg) and an ARR17477 group (n=11) receiving IV ARR17477 (5 mg/kg) before VF. All animals in Part II underwent unsupported VF (no chest compression or ventilation) for 6 min (n=13) or 8 min (n=22); closed-chest compression, ventilation and epinephrine (adrenaline) were employed after defibrillation. Part III: 12 swine were divided into two groups: control (n=6) receiving saline and an LNNA group (n=6) receiving IV LNNA (5 mg/kg). Swine underwent 6 min unsupported VF and 2 min supported VF before defibrillation. Part IV: 25 animals were studied to determine the effect of the NO donor SNAP and the angiotensin-converting enzyme inhibitor Enalaprilat on coronary perfusion pressure (CPP).. In Part I, after defibrillation, with continued ventilation, chest compression and epinephrine, 8/9 L-NNA pigs achieved ROSC versus 4/8 control pigs (p=0.11). After 60 s of CPR, 7/9 pigs in the L-NNA group achieved ROSC versus 2/8 pigs in the no-L-NNA group (p<0.05). Only 2/9 pigs receiving L-NNA required epinephrine (1 mg) after defibrillation, compared to 6/8 pigs requiring at least one dose of epinephrine in the no-L-NNA group (p<0.05). In Part II, there was no significant difference between L-NNA, ARR17477 and control pigs in ROSC. However, control pigs required 6.8+/-1.4S.E. mg epinephrine; L-NNA pigs and ARR17477 pigs required less epinephrine (3.7+/-0.7 and 3.0+/-0.3 mg, both p=0.01). Shorter chest compression was required in the L-NNA group (252+/-38 s, p<0.05) and in ARR17477 group (222+/-15 s, p<0.05) compared to the control group (405+/-77 s). In Part III, L-NNA infusion caused a significant increase in mean blood pressure at baseline, but did not change CPP throughout the experiment. In Part IV, there were no significant differences in the changes of mean blood pressure and CPP between SNAP and Enalaprilat group in all animals throughout the experiment.. NOS inhibition pre-arrest did not improve survival, but did reduce requirements for epinephrine and closed-chest compression in a swine resuscitation model.

Topics: Animals; Cardiopulmonary Resuscitation; Combined Modality Therapy; Coronary Circulation; Disease Models, Animal; Electric Countershock; Enzyme Inhibitors; Heart Arrest; Hemodynamics; Models, Cardiovascular; Nitric Oxide Synthase; Nitroarginine; Random Allocation; Sensitivity and Specificity; Survival Rate; Sus scrofa; Ventricular Fibrillation

Hyperthyroidism was induced by subcutaneous injections of L-thyroxine (T4) (0.5 mg/kg/day) for 3 days in order to investigate the effects of acute hyperthyroidism on the vasorelaxing responses to isoprenaline and acetylcholine in isolated rat aortae. In the aortae, there was no significant difference in isoprenaline-induced relaxation between hyperthyroid and control rats, however acetylcholine-induced relaxation was significantly greater in hyperthyroid rats than in control rats. N(G)-nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide (NO) synthase, reduced isoprenaline- and acetylcholine-induced relaxations in both hyperthyroid and control rats and in the presence of L-NOARG no significant difference in the acetylcholine-induced relaxation was seen between the two groups of rats. Indomethacin, a cyclo-oxygenase inhibitor, had no significant influence on both isoprenaline- and acetylcholine-induced relaxations in both control and hyperthyroid rats. 17-Octadecynoic acid (17-ODYA), a cytochrome P-450 mono-oxygenase inhibitor, reduced the both isoprenaline- and acetylcholine-induced relaxation in both hyperthyroid and control rats, and acetylcholine-induced relaxation was still greater in hyperthyroid rats than in control rats. These results indicate that an acute hyperthyroidism significantly enhances muscarinic receptor- but not adrenoceptor-mediated relaxations of the aortae and L-NOARG abolished an enhancement by acute hyperthyroidism of muscarinic receptor-mediated relaxation, suggesting that the effects may be due to an alteration in muscarinic receptor-mediated NO systems of the aortae at early stage of hyperthyroidism.

Topics: Acetylcholine; Adrenergic beta-Agonists; Animals; Aorta, Thoracic; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fatty Acids, Unsaturated; Hyperthyroidism; Isoproterenol; Male; Nitroarginine; Rats; Rats, Wistar; Receptors, Cholinergic; Vasodilation; Vasodilator Agents

Relationships between the NO synthase inhibitor and gastric and pancreaticobiliary functions measured simultaneously in the digestive state have been little studied. The aim of this study was to estimate the effect of NO synthase inhibitor on integrated digestive function in conscious dogs. A strain gauge force transducer was implanted on the gastric antrum of 6 mongrel dogs to measure gastric contractile activity and two duodenal cannulas were inserted into the proximal and distal sites to measure the gastric emptying rate and the pancreaticobiliary output into the duodenum using our novel method. Postprandial pancreatic and biliary secretion were presented as amylase and bile acid activity, respectively. Furthermore, a cervical cannula was placed into the superior vena cava as a route for the administration of NO synthase inhibitor, N omega-nitro-L-arginine (L-NNA), at a dose of 2.5 mg/kg-h. In a group given L-NNA, gastric contractile activity after ingestion was significantly enhanced, but the emptying rates of gastric solids and liquids were significantly suppressed in comparison with the control. The mean 0-1 h amylase integrated output was significantly (P < 0.05) decreased in comparison with the control, and the mean bile acid integration of 0-1 h output was also significantly (P < 0.01) decreased. A possible explanation for this observation is that smaller volumes of nutrient are delivered into the duodenum; however, it could also be that postprandial pancreaticobiliary secretion is inhibited by an alteration of blood flow or by a change in contractions of the sphincter of Oddi after the administration of L-NNA.

Topics: Animals; Biliary Tract; Disease Models, Animal; Dogs; Enzyme Inhibitors; Gastric Emptying; Nitric Oxide Synthase; Nitroarginine; Pancreas; Postprandial Period; Pyloric Antrum

In this work, we aimed to observe the changes in adrenomedullin (ADM) and its receptor-calcitonin receptor-like receptor (CL), receptor activity-modifying protein (RAMP) 1, RAMP2 and RAMP3-in cardiac ventricles and aortas of hypertensive rats, and the responsiveness of injured cardiovascular tissue to ADM, then to illustrate the protective mechanism of ADM on the cardiovascular system. Male SD rats were subjected to treatment with chronic N(G)-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide synthase. The ADM contents and cAMP production in myocardia and aortas were measured by RIA. The mRNA levels of ADM, CL, and RAMP1-3 were determined by RT-PCR. L-NNA induced severe hypertension and cardiomegaly. The ir-ADM content in plasma, ventricles and aortas in L-NNA-treated animals increased by 80%, 72% and 57% (all p<0.01), respectively. Furthermore, mRNA levels of ADM, CL, RAMP2 and RAMP3 were elevated by 91%, 33%, 50% and 72.5% (all p<0.01), respectively, in ventricles and by 95%, 177%, 74.7% and 85% (all p<0.01), respectively, in aortas. mRNA level of RAMP1 was elevated by 129% (p<0.01) in aortas but no significant difference in ventricles. The elevated mRNA levels of RAMP2 and RAMP3 were positively correlated with that of ADM in hypertrophic ventricles (r=0.633 and 0.828, p<0.01, respectively) and the elevated mRNA levels of CL, RAMP2 and RAMP3 were positively correlated with that of ADM in aortas (r=0.941, 0.943 and 0.736, all p<0.01, respectively). The response of ventricular myocardia and aortas to ADM administration potentiated, and the production of cAMP was increased by 41% and 68% (both p<0.01), respectively. ADM-stimulated cAMP generation in ventricular myocardia and aortas was blocked by administration of both ADM22-52, the specific antagonist of ADM receptor, and CGRP8-37, the antagonist of the CGRP1 receptor. The results showed an increased in cardiovascular ADM generation and an up-regulation of the gene expression of ADM and its receptor-CL, RAMP1-3 during hypertension, augmented responsiveness of ventricular myocardia and aortas of hypertensive rats to ADM, suggesting that these receptors may play a role in the cardiovascular adaptation in response to sub-chronic NO-inhibition.

Topics: Adrenomedullin; Animals; Antihypertensive Agents; Aorta; Cyclic AMP; Disease Models, Animal; Enzyme Inhibitors; Heart; Heart Ventricles; Hypertension; Intracellular Signaling Peptides and Proteins; Male; Myocardium; Nitroarginine; Peptides; Rats; Rats, Sprague-Dawley; Receptors, Calcitonin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

The aim of this investigation was to assess the role that NO plays in the antinociceptive activity of tramadol using a rat model of neuropathic pain. Thirty male Wistar rats weighing 200-250 g were randomly divided into five equal groups. The neuropathic pain model used for the study was chronic constrictive injury (CCI) model. Three weeks after the surgical procedure, each rat was tested to assess mechanical threshold in grams using an electronic algometer. After CCI was induced, tramadol hydrochloride was administered by intraperitoneal (i.p.) injection in all groups, and Nomega-nitro-L-arginine (L-NA) and L-arginine were administered i.p. or intrathecally (i.t.) depending on the group. Tramadol was administered in 10 mg/kg doses i.p., L-NA was given in 10 mg/kg doses i.p. and in 30 microg/kg doses i.t.. L-arginine was given in 10 mg/kg doses i. p. and in 50 microg/kg doses i.t.. The multiple agents were given 30 minutes apart from each administration. Intraperitoneal administration of tramadol (Group 1) only increased mechanical threshold in the rats' left hind paw, whereas in i.p. L-NA group (10 mg/kg) (Group 2) produced a significant reduction of the mean mechanical antinociceptive threshold (p<0.05). Like this, in i.t. L-NA group (30 microg/kg) (Group 4) a significant reduction of the mean mechanical antinociceptive threshold (p<0.05) was also observed. The mean threshold values in Group 2 (i.p. tramadol+i.p. L-NA) and Group 4 (i.p. tramadol+i.t. L-NA) were not significantly different. The mean threshold values in Groups 3 (i.p. tramadol+i.p. L-NA+i.p. L-arginine) and 5 (i.p. tramadol+i.t. L-NA+i.t. L-arginine) were also similar. The mean mechanical antinociceptive threshold was significantly increased in Group 3 (i.p. L-NA+L-arginine) and Group 5 (i.t. L-NA+L-arginine) when compared to Group 1 (i.p. tramadol only) (p<0.05 for both). The results of this study support the involvement of the L-arginine/nitric oxide pathway in the antinociceptive effect of tramadol in a rat model of neuropathic pain.

Topics: Analgesics; Animals; Arginine; Disease Models, Animal; Injections, Intraperitoneal; Male; Nerve Compression Syndromes; Neuralgia; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Nociceptors; Rats; Rats, Wistar; Tramadol

We used the partial protection exerted by suitable dosages of nicotinamide against the beta-cytotoxic effect of streptozotocin (STZ) to create an experimental diabetic syndrome in adult rats that appears closer to type II diabetes mellitus than other available animal models. The dosage of 230 mg/kg of nicotinamide given intraperitoneally 15 min before STZ administration (65 mg/kg i.v.) yielded animals with hyperglycemia (187.8 +/- 17.8 vs. 103.8 +/- 2.8 mg/dL in controls; P < 0.001) and preservation of plasma insulin levels. This study assessed the relationship between endothelial dysfunction and agonist-induced contractile responses in such rats. In the thoracic aorta, the acetylcholine (ACh) induced relaxation was significantly reduced and the noradrenaline (NA) induced contractile response was significantly increased in diabetic rats compared with age-matched control rats. In the superior mesenteric artery, the ACh-induced relaxation was similar in magnitude between diabetic and age-matched control rats; however, the ACh-induced endothelium-derived hyperpolarizing factor (EDHF) type relaxation was significantly weaker in diabetic rats than in the controls. The phenylephrine (PE) induced contractile response was not different between the two groups. The plasma concentration of NOx (NO2- + NO3-) was significantly lower in diabetic rats than in control rats. We conclude that vasomotor activities in conduit arteries are impaired in this type II diabetes model.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Biological Factors; Chlorides; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Hyperglycemia; Indomethacin; Insulin; Isotonic Solutions; Male; Mesenteric Artery, Superior; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Niacinamide; Nitric Oxide; Nitroarginine; Nitroprusside; Norepinephrine; Phenylephrine; Potassium; Rats; Rats, Wistar; Sodium

In experiments on the closed-chest dogs it was shown that NOS inhibition resulted in the significant alterations of hemodynamic indices (coronary and peripheral vascular resistance, cardiac output and heart rate) under local myocardial ischemia/reperfusion in comparison with control experiments. At the first time it was shown that NOS inhibition activated the autophagic destruction of cardiomyocytes in the ischemic myocardium and could reduce an area of functionally active myocardium. L-arginine administration attenuated cardio- and hemodynamic disturbances, that substantially improved the course of ischemia/reperfusion, diminished the ultrastructural changes in myocardium and prevented development of autophagic programmed cell death.

Topics: Acute Disease; Animals; Arginine; Coronary Circulation; Coronary Vessels; Disease Models, Animal; Dogs; Enzyme Inhibitors; Male; Myocardial Reperfusion Injury; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

The influence of left ventricular hypertrophy (LVH) on the endothelial function of resistance endocardial arteries is not well established. The aim of this study was to characterise the mechanisms responsible for UK-14,304 (alpha(2)-adrenoreceptor agonist)-induced endothelium-dependent dilation in pig endocardial arteries isolated from hearts with or without LVH. LVH was induced by aortic banding 2 months before determining endothelial function. Following euthanasia, hearts were harvested and endocardial resistance arteries were isolated and pressurised to 100 mmHg in no-flow conditions. Vessels were preconstricted with acetylcholine (ACh) or high external K(+) (40 mmol l(-1) KCl). Results are expressed as mean+/-s.e.m. UK-14,304 induced a maximal dilation representing 79+/-6% (n=8) of the maximal diameter. NO synthase (l-NNA, 10 micromol l(-1), n=7) or guanylate cyclase (ODQ, 10 micromol l(-1), n=4) inhibition reduced (P<0.05) UK-14,304-dependent dilation to 35+/-6 and 18+/-7%, respectively. Apamin and charybdotoxin reduced (P<0.05) to 39+/-8% (n=4) the dilation induced by UK-14,304. In depolarised conditions, however, this dilation was prevented (P<0.05). UK-14,304-induced dilation was reduced (P<0.05) by glibenclamide (Glib, 1 micromol l(-1)), a K(ATP) channel blocker, either alone (35+/-10%, n=5) or in combination with l-NNA (34+/-9%, n=4). In LVH, UK-14,304-induced maximal dilation was markedly reduced (25+/-4%, P<0.05) compared to control; it was insensitive to l-NNA (21+/-5%) but prevented either by the combination of l-NNA, apamin and charybdotoxin, or by 40 mmol l(-1) KCl. Activation of endothelial alpha(2)-adrenoreceptor induces an endothelium-dependent dilation of pig endocardial resistance arteries. This dilation is in part dependent on NO, the release of which appears to be dependent on the activation of endothelial K(ATP) channels. This mechanism is blunted in LVH, leading to a profound reduction in UK-14,304-dependent dilation.

Topics: Adenosine Triphosphate; Animals; Bradykinin; Brimonidine Tartrate; Canada; Charybdotoxin; Coronary Vessels; Disease Models, Animal; Drug Therapy, Combination; Endocardium; Endothelium, Vascular; Glyburide; Guanylate Cyclase; Hemodynamics; Hypertrophy, Left Ventricular; Indomethacin; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Oxadiazoles; Potassium Channels; Quinoxalines; Swine; Vascular Resistance; Vasodilation

To investigate the effect of NG-nitro-L-arginine (L-NNA), a nitric oxide synthase (NOS) inhibitor, on the testis cell apoptosis in morphine-dependent rats induced by naloxone and the involved mechanisms.. Forty-eight Wistar rats were randomly divided into a control group, withdrawal group and a therapeutic group. Morphine-dependent rats were given gradually increasing doses of morphine to produce morphine-dependent models, the abstinent syndrome precipitated by naloxone. The inhibiting effect of L-NNA on the abstinent syndrome, and the testis apoptosis, NOS positive cells, calmodulin (CaM) contents, superoxide dismutase (SOD) activity, and glutathione super oxidase (GSHPx) activity of the morphine-dependent rats induced by naloxone were observed and recorded by radioimmunoassay, atomic absorption spectrometry, in situ nick translation (ISNT) and NADPH-d histochemical technique.. Compared with the control rats, the function of the somesthetic motor nerves and autonomic nerves was excessive, the apoptosis and NOS positive cells in the testis were significantly increased (P < 0.05 or P < 0.01), the content of CaM and the activity of SOD and GSHPx were obviously decreased in the morphine-dependent rats induced by naloxone. But L-NNA could significantly inhibit the abstinent syndrome, decrease NOS positive cells and apoptosis, and increase CaM content and the activity of SOD and GSHPx in the testis.. Morphine dependence can induce testis cell apoptosis, an increase in testis NOS positive cells, a decrease in CaM content and the activity of SOD and GSHPx in the testis. L-NNA has the curative effect on the morphine abstinent syndrome, protects testis cells against apoptosis and improves their involved biochemical indexes.

Topics: Animals; Apoptosis; Calmodulin; Disease Models, Animal; Male; Morphine Dependence; Nitric Oxide Synthase; Nitroarginine; Random Allocation; Rats; Rats, Wistar; Spermatozoa; Testis

In the present study, we investigated the effects of N(G)-nitro-L-arginine (L-NAME), an inhibitor of nitric oxide synthase, on repeated cerebral ischemia-induced impairment of spatial memory of the 8-arm radial maze in rats. Repeated ischemia (10 min ischemia x 2 times with 1 h interval) impaired the spatial memory in the 8-arm radial maze test and produced apoptosis in the hippocampus 7 days after final occlusion, and gradually increased the NO(x)(-) levels approximately 30-180 min after the second reperfusion. Post-ischemic administration of L-NAME at a dose of 50 mg/kg, i.p. 30 min following the second occlusion, significantly attenuated the repeated ischemia-induced impairment of spatial memory in the 8-arm radial maze test and suppressed apoptosis in the hippocampus, and also significantly suppressed a delayed increase in the NO(x)(-) levels induced by repeated ischemia. However, pre-ischemic administration of L-NAME at a dose of 50 mg/kg, i.p. 30 min before the first occlusion, caused about 90% mortality (the mortality rate of vehicle-treated group was 10%). These results suggest that the delayed generation of NO(x)(-) may cause spatial memory impairment and induction of apoptosis in the hippocampus in rats subjected to repeated ischemia.

Topics: Animals; Apoptosis; Brain Ischemia; Disease Models, Animal; Enzyme Inhibitors; Hippocampus; Injections, Intraperitoneal; Injections, Intraventricular; Maze Learning; Memory; Microdialysis; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Time Factors

To demonstrate that nitric oxide (NO) contributes to free radical generation after epicardial shocks and to determine the effect of a nitric oxide synthase (NOS) inhibitor, N(G)-nitro-L-arginine (L-NNA), on free radical generation.. Free radicals are generated by direct current shocks for defibrillation. NO reacts with the superoxide (O(2).(-)) radical to form peroxynitrite (O=NOO(-)), which is toxic and initiates additional free radical generation. The contribution of NO to free radical generation after defibrillation is not fully defined.. Fourteen open chest dogs were studied. In the initial eight dogs, 40 J damped sinusoidal monophasic epicardial shocks was administered. Using electron paramagnetic resonance, we monitored the coronary sinus concentration of ascorbate free radical (Ascz.(-)), a measure of free radical generation (total oxidative flux). Epicardial shocks were repeated after L-NNA, 5 mg/kg IV. In six additional dogs, immunohistochemical staining was done to identify nitrotyrosine, a marker of reactive nitrogen species-mediated injury, in post-shock myocardial tissue. Three of these dogs received L-NNA pre-shock. After the initial 40 J shock, Ascz.(-) rose 39+/-2.5% from baseline. After L-NNA infusion, a similar 40 J shock caused Ascz.(-) to increase only 2+/-3% from baseline (P<0.05, post-L-NNA shock versus initial shock). Nitrotyrosine staining was more prominent in control animals than dogs receiving L-NNA, suggesting prevention of O=NOO(-) formation.. NO contributes to free radical generation and nitrosative injury after epicardial shocks; NOS inhibitors decrease radical generation by inhibiting the production of O=NOO(-).

Topics: Animals; Disease Models, Animal; Dogs; Electric Countershock; Electron Spin Resonance Spectroscopy; Enzyme Inhibitors; Free Radicals; Hemodynamics; Immunohistochemistry; Myocardium; Nitric Oxide Synthase; Nitroarginine; Probability; Reference Values; Risk Factors; Sensitivity and Specificity; Time Factors

Previously, the authors have reported that acetylcholine-induced vascular relaxation in epineurial arterioles of the sciatic nerve is mediated by nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). Furthermore, they have demonstrated that acetylcholine-induced vasodilation in these vessels is impaired in streptozotocin-induced (type 1) and ZDF obese (type 2) diabetic rats. In the present study, the authors sought to determine the effect of diabetes on NO- and EDHF-mediated vasodilation in epineurial arterioles. In epineurial arterioles from nondiabetic Sprague-Dawley rats, NO and EDHF are equivalent in regard to their contribution to acetylcholine-induced vascular relaxation. In contrast, NO accounts for a greater portion of acetylcholine-induced vascular relaxation in normal glycemic ZDF lean rats. Following 4 weeks of hyperglycemia, the EDHF component of acetylcholine-induced vascular relaxation was totally inhibited in both streptozotocin-induced and ZDF obese diabetic rats. Vasodilation mediated by NO was still active in epineurial arterioles from both type 1 and type 2 diabetic rat models. These data suggest that diabetes causes an impairment in EDHF-mediated vascular relaxation and that interventions directed at improving EDHF production or bioactivity may improve vascular function in epineurial arterioles in diabetes.

Topics: Acetylcholine; Animals; Arterioles; Biological Factors; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Disease Models, Animal; Endothelium, Vascular; Indomethacin; Male; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Rats, Zucker; Sciatic Nerve; Vasodilation

To investigate the effects of prostacyclin (PGI(2)) and nitric oxide (NO) in the development of hyperdynamic circulatory state on chronic portal hypertensive rats.. Sixty-six male SD rats were divided into three groups, namely intrahepatic portal hypertension (IHPH) by injection of CCl(4), prehepatic portal hypertension (PHPH) by partial stenosis of the portal vein for 2 weeks and sham-operated controls (SO). Animals in each group were divided further into 3 subgroups and received N(omega)-nitro-L-arginine (L-NNA), indomethacin and saline (as control), respectively. Splanchnic and systemic hemodynamics was measured using radioactive microsphere techniques. The NO concentration in serum was determined by nitrates-nitrites which were measured using a colorimetric method, and concentration of PGI(2) was determined using specific radioimmunoassay for its stable hydrolytic product, 6-keto-PGF(1 alpha).. The concentrations of plasma 6-keto-PGF(1 alpha) and serum nitrates + nitrites in IHPH rats (1 123.85 +/- 153.64; 73.34 +/- 4.31) and in PHPH rats (891.88 +/- 83.11; 75.21 +/- 6.89) were significantly higher than those of SO rats (725.53 +/- 105.54;58.79 +/- 8.47). L-NNA and indomethacin could decrease the concentrations of plasma 6-keto-PGF(1 alpha) and serum nitrates + nitrites in IHPH and PHPH rats (P < 0.05). At the same time, CI, FPP and PVI were lowered while MAP, TPR and SVR were increased (P < 0.05). After deduction of NO action, there were no significant correlation between plasma PGI(2) level and hemodynamic parameters such as CI, TPR, PVI and SVR. However, after deduction of PGI(2) action, NO was still correlated highly with those hemodynamic parameters.. It is NO rather then PGI(2) that is a mediator in the formation and development of hyperdynamic circulatory state in chronic portal hypertensive rats.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Cyclooxygenase Inhibitors; Disease Models, Animal; Enzyme Inhibitors; Epoprostenol; Hemodynamics; Hypertension, Portal; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Random Allocation; Rats; Rats, Sprague-Dawley

The aim of this study was to investigate coronary vascular responses, particularly NO-dependent, in the non-ischemic miocardium during local acute myocardial ischemia/reperfusion. The experiments were performed on the dogs with closed chest. Occlusion of a branch of the coronary artery resulted in a dilatation of the coronary vessels within the intact part of the myocardium. Neither inhibition of prostanoid production and KATP-channels, nor administration of atropine sulfate and dissection of the vagus nerve altered coronary dilatation within the non-ischemic myocardium. Whereas inhibition of NOS by L-NNA (50 mg/kg) completely changed it after coronary occlusion, furthermore coronary resistance temporally increased. Thus, the most reliable mechanism of that response was NO-dependent.

Topics: Acute Disease; Animals; Coronary Circulation; Coronary Vessels; Disease Models, Animal; Dogs; Electrocardiography; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitroarginine; Vasodilation

Arteries from deoxycorticosterone acetate (DOCA)-salt and N(omega)-nitro-L-arginine (L-NNA) hypertensive but not normotensive rats develop spontaneous tone. LY294002 and wortmannin, phosphoinositide 3-kinase (PI3-kinase) inhibitors, eliminate spontaneous tone. We hypothesized that PI3-kinase protein and/or activity was increased in hypertension and contributed to the observed enhanced contractility. PI3-kinase activity assays revealed 2-fold higher activity in thoracic aorta from DOCA-salt [systolic blood pressure (SBP)=184+/-5 mm Hg] compared with sham rats (SBP=111+/-2 mm Hg). Western analyses of aortic homogenates revealed the presence of p85alpha, p110alpha, p110beta, and p110delta but not p110gamma PI3-kinase subunits; p110delta protein was elevated in aorta of hypertensive rats as compared with sham. Aortic homogenates from L-NNA rats also had elevated p110beta protein density, but neither L-NNA nor DOCA-salt had differences in p85alpha and p110alpha. Total Akt density was unaltered, but pAkt was significantly lower in homogenates from DOCA-salt rats. LY294002 (20 micromol/L) and nifedipine (50 nmol/L) abolished Ca2+-induced spontaneous tone in aorta from DOCA-salt rats. However, LY294002 did not alter BayK8644-induced contraction, indicating that LY294002 does not inhibit L-type Ca2+ channels directly. PTEN (phosphatase and tensin homolog) and pPTEN were expressed but not different in aorta from DOCA-salt and sham rats. LY294002 corrected the enhanced contraction to KCl and norepinephrine in aorta from DOCA-salt rats. These data support an increase in PI3-kinase activity and p110delta density in aorta from L-NNA and DOCA-salt rats. Importantly, this increase contributes to the enhanced contractility observed in two models of hypertension.

Topics: Animals; Aorta, Thoracic; Blotting, Western; Calcium; Calcium Channel Agonists; Calcium Channel Blockers; Desoxycorticosterone; Disease Models, Animal; Enzyme Activation; Enzyme Inhibitors; Hypertension; In Vitro Techniques; Male; Nitroarginine; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphoric Monoester Hydrolases; Protein Serine-Threonine Kinases; Protein Subunits; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Rats; Rats, Sprague-Dawley; Tumor Suppressor Proteins; Vasoconstriction; Vasoconstrictor Agents

This study investigated the role of nitric oxide (NO) in the control of right coronary (RC) blood flow at rest and during acute pulmonary hypertension. Experiments were performed in seven chronically instrumented, conscious dogs. NO synthesis was inhibited by systemic administration of N(omega)-nitro-L-arginine (LNA, 35 mg/kg). Inflation of a balloon in the main pulmonary artery raised right ventricular (RV) peak systolic pressure from 34 +/- 2 to 47 +/- 3 mmHg before LNA and from 37 +/- 2 to 47 +/- 3 mmHg after LNA, but did not affect mean systemic arterial pressure. RV O(2) consumption (MVO(2)) increased from 4.4 +/- 0.7 to 6.1 +/- 0.7 ml/min/100 g. 82 % of the elevated RV MVO(2) was provided by RC blood flow, which increased from 46 +/- 7 to 61 +/- 8 ml/min/100 g. After LNA, resting RV MVO(2) and RC flow fell. RC venous PO(2) fell, but RV lactate uptake was not altered. During pulmonary hypertension, the increase in RC blood flow was blunted by LNA, so that only 66 % of the elevated RV MVO(2) was supplied by increased RC flow. Analysis of O(2) supply variables as functions of RV MVO(2) further demonstrated a significant role of NO in regulating RC flow at rest and during moderate pulmonary hypertension. Conclusions NO is required for the RC hyperemic response to acute pulmonary hypertension as well as for normal resting RC blood flow. After blockade of NO synthesis, RV O(2) supply at rest and during pulmonary hypertension was sustained by increased RV O(2) extraction.

Topics: Animals; Blood Pressure; Coronary Circulation; Coronary Vessels; Disease Models, Animal; Dogs; Female; Hypertension, Pulmonary; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen Consumption; Regional Blood Flow

Arterial hyperresponsiveness to serotonin (5-hydroxytryptamine, 5-HT) is observed in experimental models and human forms of hypertension. Presently, we test the hypothesis that the 5-HT(2B) receptor is up-regulated and necessary for maintaining elevated blood pressure in a rat made hypertensive by the nitric-oxide synthase inhibitor N(omega)-nitro-L-arginine (LNNA; 0.5 g/l). After 2 weeks of treatment, thoracic aorta were removed from LNNA hypertensive (systolic blood pressure = 189 +/- 5 mm Hg) and sham normotensive rats (121 +/- 1 mm Hg), denuded, and mounted into isolated tissue baths for measurement of isometric contraction. In sham tissues, 5-HT-induced contraction was mediated by the 5-HT(2A) receptor as evidence by a parallel rightward shift in response to 5-HT by the 5-HT(2A/2C) receptor antagonist ketanserin (10 nM) and lack of shift by the 5-HT(2B) receptor antagonist 6-methyl-1,2,3,4-tetrahydro-1-[3,4-dimethoxyphenyl)methyl]-9H-pyrido[3,4-b]indole hydrochloride (LY272015) (10 nM). In contrast, LY272015 produced a 4-fold rightward shift to 5-HT in aorta from LNNA hypertensive rats, and blockade by ketanserin did not occur at low concentrations of 5-HT. Maximal contraction to the 5-HT(2B) receptor agonist 1-[5-(2-thienylmethoxy)-1H-3-indolyl]propan-2-amine hydrochloride was significantly greater in LNNA hypertensive rats (percentage of phenylephrine contraction in sham = 7 +/- 4, and in LNNA = 61 +/- 7%). 5-HT(2B) receptor protein was present in aortic homogenates from sham and LNNA rats, but the density of 5-HT(2B) receptor protein in LNNA homogenates was 300% that in sham. Importantly, the 5-HT(2B) receptor antagonist LY272015 reduced blood pressure of the LNNA hypertensive but not the sham normotensive rats. Thus, these data suggest that the up-regulated 5-HT(2B) receptor in the LNNA hypertensive rats is physiologically activated to maintain elevated blood pressure.

Topics: Animals; Antihypertensive Agents; Aorta, Thoracic; Disease Models, Animal; Endothelium, Vascular; Humans; Hypertension; In Vitro Techniques; Ketanserin; Male; Nitroarginine; Organic Chemicals; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT2B; Receptors, Serotonin; Serotonin; Serotonin Receptor Agonists; Vasoconstriction

Because nitric oxide (NO) regulates cardiac and vessel contraction, we compared the expression and activity of the endothelial NO synthase (eNOS) and caveolin, which tonically inhibits eNOS in normal and hypertrophic cardiomyopathic hearts. NOS activity (L-[(3)H]citrulline formation), eNOS immunostaining, and caveolin abundance were measured in heart tissue of 23 mongrel dogs before and at 3 and 7 wk of perinephritic hypertension (PHT). Hemodynamic parameters in vivo and endothelial NO-dependent relaxation of macro- and coronary microvessels in vitro were assessed in the same animals. eNOS immunostaining and total calcium-dependent NOS activity decreased at 7 wk in all four heart cavities (in left ventricle, from 17.0 +/- 1.3 to 0.2 +/- 0.2 fmol. min(-1). mg protein(-1), P < 0.001). Caveolin-1 and -3 also decreased in PHT dog hearts. Accordingly, basal vascular tone was preserved, but maximal endothelial NO-dependent relaxation was impaired in all vessels from 7-wk PHT dogs. The latter had preserved systolic function but impaired diastolic relaxation [relaxation time constant (T(1)), 25.1 +/- 0.9 vs. 22.0 +/- 1 ms in controls; P < 0.05]. Peripheral infusion of the NOS inhibitor N(G)-nitro-L-arginine methyl ester increased mean aortic pressure in both groups and reduced diastolic (T(1), 31.9 +/- 1.4 ms) and systolic function in PHT dogs (DP40, 47.5 +/- 2.5 vs. 59.4 +/- 3.8 s(-1) in control animals). In conclusion, both eNOS and caveolin proteins are decreased in the hypertrophic hearts of PHT dogs. This is associated with altered maximal (but not basal) vascular relaxation and impaired diastolic function. Further degradation of cardiac function after NOS inhibition suggests a critical role of residual NOS activity, probably supported by the concurrent downregulation of caveolin.

Topics: Animals; Cardiomyopathy, Hypertrophic; Caveolin 1; Caveolins; Coronary Circulation; Disease Models, Animal; Dogs; Echocardiography; Hemodynamics; Hypertension, Renal; Immunoblotting; Immunohistochemistry; Mesenteric Arteries; Microcirculation; Muscle Contraction; Myocardium; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Regression Analysis; Ventricular Function, Left

To evaluate the effect of EDDF a new erythrocyte-derived depressing factor, on the NO/cGMP pathway in aorta of normal rats and rat, with hypertension induced by L-NNA.. Thirty male Wistar rats aged 10 weeks were divided into two groups: L-NNA group and control group, 15 rats for each group. L-N(G)-nitro-arginine (L-NNA) was injected into the abdominal cavity of the rats in the L-NNA group at dose of 15 mg/kg twice a day for four weeks. Normal saline was injected the same way in the control group. The levels of cGMP in aorta and plasma were measured by radioimmunoassay and (3)H-L-arg incorporation. NOS was measured by immunohistochemistry.. One day after injection of L-arg, the blood pressure of the experimental rats began to rise remarkably (18.8 kPa vs 16.4 kPa, P < 0.05), and then remained at a high level. The L-arg. transfer rate (pmol small middle dotmg(-1) small middle dotpr small middle dotmin(-1)) of aorta in L-NNA group was significantly lower than that of control group (13.0 +/- 0.9 vs 16.8 +/- 1.2 P < 0.05). After incubation with EDDF (10(-4) g/ml), the L-arg transfer rate and cGMP level of aorta were remarkably increased in normal rats (20.1 +/- 0.9 vs 16.8 +/- 1.2, P < 0.05 and 233 +/- 14 vs 187 +/- 10, P < 0.05). The L-arg transfer rate and cGMP level of aorta remained unchanged afeter incubation with EDDF in the L-NNA group (13.0 +/- 0.9 vs 13.2 +/- 0.3 and 148 +/- 16 vs 186 +/- 12). The cGMP level (pmol/g) of aorta in L-NNA group were obviously lower than that of control rats (148 +/- 16 vs 186 +/- 12, P < 0.05). Immunohistological staining of NOS in aorta was obviously lighter in L-NNA group than in control group. The immunohistochemical staining intensity in aorta remained the same after incubation with EDDF in L-NNA group.. The NO/cGMP pathway might be in charge of vasodilation mechanism of EDDF.

Topics: Animals; Aorta; Blood Proteins; Cyclic GMP; Disease Models, Animal; Humans; Hypertension; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Vasodilation

Arterial hypertension (AH) is characterized by reduced nitric oxide (NO) biosynthesis, vasoconstriction, and reduced microvascular density. In this study we asked whether AH also reduces the number of microvessels by impairing angiogenesis. AH was induced in Dahl salt-sensitive rats (DSS) with a salt diet and in Wistar-Kyoto rats by inhibiting NO formation with Nomega-nitro-L-arginine (NNA). Three weeks after induction of AH, two wound chambers containing collagen I (Vitrogen) were sutured into the mesenteric cavity of each animal. After additional 14 days, wound chamber neovascularization and the extent of vascularized connective tissue ingrowth were quantified. In NNA-induced AH, the number of newly formed vessels and the ingrowth of vascularized connective tissue into the wound chamber decreased as compared to controls. However, the number of newly formed vessels and the ingrowth of vascularized connective tissue did not change with increasing blood pressure in salt-fed DSS rats as compared to those fed a normal diet. Inhibition of NO biosynthesis, but not necessarily elevating blood pressure, reduces angiogenesis. Microvascular rarefaction in AH may be partially due to reduced angiogenesis because of impaired NO biosynthesis.

Topics: Animals; Blood Pressure; Disease Models, Animal; Hypertension; Neovascularization, Pathologic; Nitric Oxide; Nitroarginine; Rats; Rats, Inbred Dahl; Rats, Inbred WKY; Sodium Chloride

We tested the hypothesis that carbon monoxide might participate in the modulation of hypoxic pulmonary vasoconstriction (HPV) by prostacyclin (PGI2) and nitric oxide.. Prospective, interventional study.. University laboratory.. Nineteen intact anesthetized mongrel dogs.. Right heart catheterization for the measurements of mean pulmonary artery pressure (Ppa), left atrial pressure estimated from occluded Ppa (Ppao), pulmonary capillary pressure (Pcp) calculated from the Ppa decay curve after balloon occlusion, and cardiac output (Q); inferior vena cava balloon for the control of Q by manipulation of venous return; ventilation in hyperoxia (fraction of inspired O2, 0.4) or in hypoxia (Fio2, 0.1); inhibition of cyclooxygenase by indomethacin (Indo); inhibition of nitric oxide synthase by NG-nitro-l-arginine (L-NA); inhibition of heme oxygenase by mesoporphyrin IX (SnMP); inhalation of nitric oxide (20 ppm); and inhalation of carbon monoxide (100 ppm).. The first seven dogs were weak responders to hypoxia as assessed by a hypoxia-induced increase in the gradient between Ppa and Ppao, measured at one level of Q kept constant, by an average of only 2 mm Hg (p = NS). This HPV was markedly increased by the combined administration of Indo and L-NA. A further enhancement of HPV was observed after the addition of SnMP, leading to severe pulmonary hypertension with an average increase in Ppa to 39 mm Hg. Inhaled nitric oxide inhibited HPV only after the combined administration of Indo, L-NA, and SnMP. Inhaled carbon monoxide had no effect. The next 12 dogs were stronger responders to hypoxia, as assessed by a hypoxia-induced increase in the gradient between Ppa and Ppao, measured at several levels of Q, by an average of 3 mm Hg (p <.05). This HPV was of the same magnitude after administration of placebo (n = 6) or SnMP (n = 6). Addition of Indo enhanced HPV to the same extent in the placebo and in the SnMP groups. Addition of L-NA induced a further enhancement of HPV, which was, however, greater in the SnMP group. There was a slight increase in the capillary-venous segment relative to the arterial segment in hypoxic conditions, but the partitioning of pulmonary vascular resistance was otherwise unaffected by nitric oxide, carbon monoxide, or PGI2.. Endogenous carbon monoxide modulates canine HPV only in the absence of nitric oxide. The vasodilation mediated by nitric oxide, PGI2, or carbon monoxide is essentially distributed between proximal and distal sites proportionally to the degree of constriction produced during hypoxia.

Topics: Administration, Inhalation; Animals; Carbon Monoxide; Cyclooxygenase Inhibitors; Disease Models, Animal; Dogs; Drug Evaluation, Preclinical; Epoprostenol; Hemodynamics; Hypoxia; Indomethacin; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Prostaglandin-Endoperoxide Synthases; Pulmonary Circulation; Vasoconstriction

To investigate if retinal blood flow decreases with progression of the disease in Abyssinian cats with progressive retinal atrophy (PRA), to examine if the choroidal blood flow was affected by the disease, and to determine the uptake of glucose and formation of lactate in the outer retina.. Local blood flow in different parts of the eye was determined with radioactive microspheres, in 9 normal cats and in 10 cats at different stages of PRA. Three blood flow determinations were made in each animal, during control conditions, after IV administration of indomethacin and after subsequent administration of N(omega)-nitro-L-arginine (L-NA). Blood samples from a choroidal vein and a femoral artery were collected to determine the retinal formation of lactate and uptake of glucose.. In Abyssinian cats with PRA (n = 10), the retinal blood flow was significantly (P < or = 0.01) lower than in normal cats (n = 9) during control conditions, 6.4 +/- 1.7 compared with 14.1 +/- 1.9 g min(-1) x (100 g)(-1). The vascular resistance in the iris and ciliary body was significantly higher in the cats at a late stage of PRA, both compared with normal cats and to cats at an early stage of the disease, whereas the choroidal vascular resistance was not significantly affected. Indomethacin had no effect on ocular blood flows in normal cats, but in cats with PRA, iridal blood flow was more than doubled after indomethacin. The retinal formation of lactate was significantly (P < or = 0.001) lower in cats with PRA than in normal cats, 0.111 +/- 0.035 (n = 8) compared with 0.318 +/- 0.024 (n = 8) micromol x min(-1). The uptake of glucose was not significantly different in cats with PRA.. Retinal blood flow is severely decreased in Abyssinian cats at a late stage of retinal degeneration, whereas the choroidal microcirculation is not significantly affected by the disease. At a late stage of retinal degeneration, vascular resistance in the iris is significantly increased, which at least in part could be caused by cyxlooxygenase products.

Topics: Animals; Blood Flow Velocity; Blood Glucose; Cardiovascular Agents; Cats; Choroid; Disease Models, Animal; Disease Progression; Enzyme Inhibitors; Female; Heart Rate; Indomethacin; Lactic Acid; Male; Nitroarginine; Regional Blood Flow; Retina; Retinal Degeneration; Retinal Vessels

The pulmonary disease of cystic fibrosis (CF) is characterized by persistent airway obstruction, which has been attributed to chronic endobronchial infection and inflammation. The levels of exhaled nitric oxide (NO) are reduced in CF patients, which could contribute to bronchial obstruction through dysregulated constriction of airway smooth muscle. Because airway epithelium from CF mice has been shown to have reduced expression of inducible NO synthase, we examined airway responsiveness and relaxation in isolated tracheas of CF mice. Airway relaxation as measured by percent relaxation of precontracted tracheal segments to electrical field stimulation (EFS) and substance P, a nonadrenergic, noncholinergic substance, was significantly impaired in CF mice. The airway relaxation in response to prostaglandin E2 was similar in CF and non-CF animals. Treatment with the NO synthase inhibitor NG-nitro-L-arginine methylester reduced tracheal relaxation induced by EFS in wild-type animals but had virtually no effect in the CF mice. Conversely, exogenous NO and L-arginine, a NO substrate, reversed the relaxation defect in CF airway. We conclude that the relative absence of NO compromises airways relaxation in CF, and may contribute to the bronchial obstruction seen in the disease.

Topics: Animals; Arginine; Bronchoconstriction; Cystic Fibrosis; Dinoprostone; Disease Models, Animal; Electric Stimulation; Enzyme Inhibitors; Female; In Vitro Techniques; Male; Mice; Mice, Inbred CFTR; Muscle Relaxation; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Substance P; Trachea

The comparison of the reactivity to norepinephrine (NE) and angiotensin II (A II) of isolated mesenteric blood vessels obtained from rats simultaneously poisoned with lead and cadmium to those responses of rats treated singly with lead or cadmium was performed. Male Buffalo rats aged 6-8 weeks were administered intragastrically with lead (35 mg Pb/kg body wt.) and/or cadmium (5 mg Cd/body wt.), once a week for a period of 7 weeks. Control rats were given equimolar amounts of sodium acetate and/or sodium chloride. Changes in mesenteric vascular resistance due to NE and A II injections were measured ex vivo as an increase in perfusion pressure in vessels prepared by McGregor's method. The dose-response curve for NE (0.01-5.0 microg) determined for vessels of rats poisoned simultaneously with lead and cadmium was shifted to the left in comparison to controls (not poisoned rats), similarly to these determined for rats poisoned with lead or cadmium. ED(50) NE pointed out in the control group (0.83+/-0.5 microg) was significantly greater than in metal treated groups (0.44+/-0.09; 0.45+/-0.26 and 0.5+/-0.11 microg in lead, cadmium, lead and cadmium-treated rats, respectively). This study indicated a tachyphylaxis in responses of isolated mesenteric vessels to A II injected in increasing doses, and the weaker, in comparison to controls, response of vessels of rats poisoned with lead and/or cadmium to A II at a dose of 0.4 microg. The decreasing response to A II could result from changes in calcium ions transport through L-type channels in vascular smooth muscle cells, because verapamil (2.0 microM) inhibited the A II-induced vasoconstriction more weakly in rats poisoned with metals than in controls. Inhibitor of prostaglandins synthesis, ketoprofen (200 microg/ml per min.) attenuated the pressor effect of NE in blood vessels obtained from all rats, but this effect was less potent in arteries of cadmium poisoned rats. Ketoprofen also inhibited the vasoconstrictory action of A II in all groups, but this effect was lower in vessels of rats poisoned simultaneously with lead and cadmium. We suggest that the release of vasoactive prostaglandins as a consequence of endothelial angiotensin receptor stimulation changes more under the influence of metals administered to rats simultaneously than under the influence or lead or cadmium administered singly. Treatment with a nitric oxide synthase inhibitor (L-NOARG; 22 microg/ml per min.) potentiated a NE-induced pressor respon

Topics: Analysis of Variance; Angiotensin II; Animals; Cadmium Poisoning; Calcium; Dinoprostone; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; In Vitro Techniques; Ketoprofen; Lead Poisoning; Male; Mesenteric Arteries; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Norepinephrine; Papaverine; Potassium Chloride; Rats; Rats, Inbred BUF; Receptors, Angiotensin; Vasoconstriction; Vasoconstrictor Agents; Verapamil

Recent studies suggest that some of the beneficial effects of 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) may be due to their cholesterol-lowering independent effects on the blood vessels. Chronic inhibition of endothelial nitric oxide (NO) synthesis by oral administration of N(omega)-nitro-L-arginine methyl ester (L-NAME) to rats induces early vascular inflammation as well as subsequent arteriosclerosis. The aim of the study is to test whether treatment with statins attenuates such arteriosclerotic changes through their cholesterol-lowering independent effects. We investigated the effect of statins (pravastatin and cerivastatin) on the arteriosclerotic changes in the rat model. We found that treatment with statins did not affect serum lipid levels but markedly inhibited the L-NAME-induced vascular inflammation and arteriosclerosis. Treatment with statins augmented endothelial NO synthase activity in L-NAME-treated rats. We also found the L-NAME induced increase in Rho membrane translocation in hearts and its prevention by statins. Such vasculoprotective effects of statins were suppressed by the higher dose of L-NAME. In summary, in this study, we found that statins such as pravastatin and cerivastatin inhibited vascular inflammation and arteriosclerosis through their lipid-lowering independent actions in this model. Such antiarteriosclerotic effects may involve the increase in endothelial NO synthase activity and the inhibition of Rho activity.

Topics: Animals; Anti-Inflammatory Agents; Arteriosclerosis; Blood Pressure; Chemokine CCL2; Coronary Vessels; Disease Models, Animal; Dose-Response Relationship, Drug; Gene Expression Regulation; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Immunohistochemistry; Lipids; Macrophages; Male; Monocytes; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide Synthase; Nitrites; Nitroarginine; Peptidyl-Dipeptidase A; Pravastatin; Proliferating Cell Nuclear Antigen; Pyridines; Rats; Rats, Inbred WKY; rhoA GTP-Binding Protein; RNA, Messenger; Systole; Transforming Growth Factor beta; Transforming Growth Factor beta1

The role of endothelium-derived nitric oxide (NO) in the metabolic control of coronary blood flow (CBF) in heart failure (HF) is poorly understood, so the present study investigated the effects of inhibitors of NO synthesis on the response of CBF to changes in myocardial oxygen consumption (MVO2) in dogs with HF produced by rapid ventricular pacing and in control dogs. The CBF, MVO2, and other hemodynamic parameters were measured in anesthetized animals. Before infusion of Nomega-nitro-L-arginine methyl ester (L-NAME), the increases in CBF and MVO2 during pacing tachycardia were not significantly different between the control and HF dogs. Intracoronary infusion of L-NAME did not alter the responses of CBF or MVO2 to pacing tachycardia in the control dogs, but in the HF dogs, it reduced the CBF response to pacing tachycardia without altering the tachycardia-induced changes in MVO2. Intracoronary infusion of L-arginine reversed the effect of L-NAME. These results suggest that in HF dogs NO contributes to the regulation of CBF in response to an increased metabolic demand.

Topics: Animals; Cardiomyopathy, Dilated; Coronary Circulation; Coronary Vessels; Disease Models, Animal; Dogs; Energy Metabolism; Enzyme Inhibitors; Heart Failure; Hemodynamics; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitroarginine; Pacemaker, Artificial; Vasodilation

The hypertensive rat model was made by chronic stress of electric foot-shocks and noises. On such hypertensive rats, when anesthetized with urethane and chloralose, the electroacupuncture (EA) to bilateral "Zusanli (st.36)" acupoints for 20 min, could result in a depressor (including both systolic and diastolic pressure) and bradycardiac response as well as an attenuation in the maximum of left ventricular pressure, end diastolic pressure and +/-dp/dt. In power spectrum analysis of heart rate variability aspect, EA could increase all total variance, very low frequency component, low frequency component and the ratio of low frequency component and high frequency component. When EA with microinjection of N(omega) - Nitro- L-Arginine , a blocker of the formation of nitric oxide, into the ventral periaqueductal gray matter (vPAG), the above effects of EA were abolished or reduced significantly. The results suggest that the depressor effect of EA on stress-induced hypertensive rats might be mediated by nitric oxide in the vPAG due to activation of sympathetic inhibitory system and by attenuated cardiac activities.

Topics: Acupuncture Points; Animals; Blood Pressure; Disease Models, Animal; Electroacupuncture; Heart Rate; Hypertension; Male; Nitric Oxide; Nitroarginine; Periaqueductal Gray; Rats; Rats, Wistar; Stress, Physiological

The potential interaction between cyclooxygenase (Cox) and NO metabolic pathways in the control of local tumor growth was evaluated. Mice bearing either a sarcoma-derived tumor (C57B1; MCG 101) or a malignant melanoma (C3H/HeN; K1735-M2) were used. These models were principally different because they demonstrate, in tumor hosts, conditions with and without cancer cachexia, seemingly related to high and low production of prostanoids, respectively. Cox inhibitors (Cox-1 and Cox-2) decreased tumor growth by 35-40% in MCG 101-bearing mice but had no such effect on melanoma-bearing mice, despite the expression of the Cox-2 protein in melanoma cells. Indomethacin reduced prostanoid production in both tumor (MCG 101) and host tissues and reduced tumor cell proliferation, mainly in vivo. Nitric oxide synthase (NOS) inhibitors (N(omega)-nitro-L-arginine methyl ester and N(omega)-nitro-L-arginine) reduced tumor growth in vivo by approximately 50% in both tumor models. Tumor growth reduction, related to NOS inhibition, was unrelated to prostanoid production and was an in vivo phenomenon in both tumor models. Specific inhibitors of inducible NOS activity, unexpectedly, had no effect in any tumor model, although inducible NOS protein was present in tumor tissues in large amounts. A combination of Cox and NOS inhibitors had no additive effect on tumor growth (MCG 101). Cox inhibition increased tumor tissue (MCG 101) expression of cNOS mRNA but had no significant effect on tumor tissue expression of the transferrin receptor, vascular endothelial growth factor, or basic fibroblast growth factor. NOS inhibition increased tumor tissue content of cNOS mRNA but showed as well a trend to increase mRNA content of the transferrin receptor and vascular endothelial growth factor. Our results suggest that NOS inhibitors can decrease the local growth of tumors that are either responsive or unresponsive to Cox inhibition. This effect may reflect cross-talk between Cox and NOS pathways within or among tumor cells, or it may represent unrelated effects on tumor and host cells. Whether NO inhibition may be used therapeutically in clinical tumors that are unresponsive to eicosanoid intervention remains to be evaluated.

Topics: Animals; Cachexia; Dinoprostone; Disease Models, Animal; Enzyme Inhibitors; Female; Gene Expression Regulation; Growth Substances; Immunohistochemistry; Indans; Indomethacin; Iodine Radioisotopes; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Neoplasms, Experimental; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitroarginine; Prostaglandin-Endoperoxide Synthases; Prostaglandins; RNA, Messenger; Tumor Cells, Cultured

Lipopolysaccharide (LPS) derived from the bacterial cell wall activates the inflammatory response in the tissue but the role of LPS in the pathogenesis of pancreatic damage and in the activation of NO system in the pancreas has not been fully explained. The aim of this study was to investigate the effect of repeated administration of LPS to the rats on the integrity of the pancreas, on the ability of isolated pancreatic acini to secrete the amylase and on the plasma level of tumor necrosis factor alpha (TNFalpha). The role of NO in the pancreatic resistance to the damage was assessed in animals subjected to repeated administration of LPS. To induce pancreatic damage one group of rats received intraperitoneal (i.p.) injection of LPS (from E. coli) every day during 5 consecutive days (10 mg/kg--day). Another groups of animals were given N(G)-nitro-L-arginine (L-NNA), an inhibitor of NO synthase (NOS) (20 mg/kg i.p.) alone or in combination with L-arginine (100 mg/kg i.p.), 30 min prior to each LPS injection. Plasma level of TNFalpha was determined by ELISA kit. Repeated administration of LPS produced mild pancreatic inflammation that was most pronounced at day 5 of LPS treatment and manifested as edema, neutrophil infiltration and hemorrhage of the pancreas. The survival rate after 5 days treatment with LPS was 87.5%. Pancreatic weight, plasma levels of TNFalpha and amylase, pancreatic blood flow (PBF) and NO generation by pancreatic acini were markedly increased in rats subjected to repeated administration of LPS whereas the amylase response of isolated pancreatic acini to pancreatic secretagogues was significantly attenuated. Suppression of NOS by L-NNA resulted in a dramatic increase in the mortality of the animals reaching 50% and significantly increased inflammatory changes in the pancreatic tissue, decreased PBF, abolished the ability of pancreatic acini to release NO and to secrete amylase. Pancreatic weight and plasma levels of amylase and TNFalpha significantly increased in the group of rats treated with combination of LPS+L-NNA as compared to the animals received LPS alone. Addition of L-arginine to L-NNA+LPS administration reversed all harmful effects produced by L-NNA in the pancreas. We conclude that repeated administration of high doses of bacterial LPS to the rats could induce pancreatic tissue damage by itself, however, it is not able to produce severe pancreatitis. Suppression of NO generation significantly aggravates the pancreatic lesion

Topics: Acute Disease; Amylases; Animals; Disease Models, Animal; Enzyme Inhibitors; Lipopolysaccharides; Male; Nitric Oxide; Nitroarginine; Organ Size; Pancreas; Pancreatitis; Rats; Rats, Wistar; Regional Blood Flow; Survival Analysis; Tumor Necrosis Factor-alpha

We studied the antithrombotic activity of 2-acetoxybenzoate 2-[1-nitroxy-methyl]-phenyl ester (NCX 4016), a novel nitric oxide (NO)-releasing aspirin derivative, in vivo in different animal models of platelet-dependent and independent pulmonary thromboembolism and compared it with that of aspirin. NCX 4016 protected mice from death induced by the intravenous (i.v.) injection of collagen plus epinephrine, of 9,11-dideoxy-11alpha, 9alpha-epoxymethano-prostaglandin F(2alpha) (U46619) and of thrombin while aspirin was only active against collagen plus epinephrine. The drop in platelet count and number of lung emboli were reduced by NCX 4016 more effectively than aspirin. NCX 4016 protected mice also from mechanical pulmonary embolism (i.v. injection of hardened rat red blood cells) while aspirin was ineffective. In rabbits, NCX 4016 significantly reduced the accumulation of [111In]oxine-labeled platelets in the pulmonary vasculature induced by collagen and by thrombin while aspirin produced reductions which were significant only versus collagen. In conclusion, NCX 4016 exerts a more pronounced antithrombotic activity than aspirin in vivo in two different animal species, largely due to a deeper inhibitory effect on platelets. NCX 4016 may represent a better antithrombotic agent than aspirin.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aspirin; Disease Models, Animal; Dose-Response Relationship, Drug; Injections, Intravenous; Lung; Male; Mice; Nitroarginine; Platelet Aggregation Inhibitors; Platelet Count; Pulmonary Artery; Pulmonary Embolism; Rabbits; Thrombin; Thrombosis

The cecal ligation and puncture (CLP) model was used to investigate whether failure of neutrophil migration occurs in sepsis and whether it correlates with disease outcome. It was observed that the severity of sepsis correlates with the number of punctures in the cecum: mice with 2 punctures (sublethal [SL]-CLP) developed mild peritonitis (100% survived), whereas mice with 12 punctures (lethal [L]-CLP) developed severe peritonitis and bacteremia that evolved to sepsis (none survived). The production of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-10 was higher in L-CLP than in SL-CLP mice. The impairment of neutrophil migration to the peritoneum and to the cecum wall was observed only in L-CLP mice. This phenomenon was shown to be mediated by nitric oxide, because aminoguanidine prevented the failure of neutrophil migration and improved the survival of L-CLP animals. In conclusion, impairment of neutrophil migration is a crucial event in the worsening of sepsis, and nitric oxide seems to be responsible for the phenomenon.

Topics: Animals; Ascitic Fluid; Bacteremia; Cell Movement; Colony Count, Microbial; Cytokines; Disease Models, Animal; Enzyme Inhibitors; Guanidines; Heart; Liver; Lung; Male; Mice; Mice, Inbred C57BL; Neutrophils; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Peritoneal Cavity; Peritoneal Diseases; Sepsis; Wounds, Penetrating

Angiotensin-converting enzyme (ACE) inhibitor improves the impaired hyperpolarization and relaxation to acetylcholine (ACh) via endothelium-derived hyperpolarizing factor (EDHF) in arteries of spontaneously hypertensive rats (SHR). We tested whether the angiotensin type 1 (AT(1)) receptor antagonist also improves EDHF-mediated responses and whether the combined AT(1) receptor blockade and ACE inhibition exert any additional effects. SHR were treated with either AT(1) receptor antagonist TCV-116 (5 mg. kg(-1). d(-1)) (SHR-T), enalapril (40 mg. kg(-1). d(-1)) (SHR-E), or their combination (SHR-T&E) from 8 to 11 months of age. Age-matched, untreated SHR (SHR-C) and Wistar Kyoto (WKY) rats served as controls (n=8 to 12 in each group). Three treatments lowered blood pressure comparably. EDHF-mediated hyperpolarization to ACh in mesenteric arteries in the absence or presence of norepinephrine was significantly improved in all treated SHR. In addition, the hyperpolarization in the presence of norepinephrine was significantly greater in SHR-T&E than in SHR-E (ACh 10(-5) mol/L with norepinephrine: SHR-C -7; SHR-T -19; SHR-E -15; SHR-T&E -22; WKY -14 mV). EDHF-mediated relaxation, assessed in the presence of indomethacin and N:(G)-nitro-L-arginine, was markedly improved in all treated SHR. Hyperpolarization and relaxation to levcromakalim, a direct opener of ATP-sensitive K(+)-channel, were similar in all groups. These findings suggest that AT(1) receptor antagonists are as effective as ACE inhibitors in improving EDHF-mediated responses in SHR. The beneficial effects of the combined AT(1) receptor blockade and ACE inhibition appears to be for the most part similar to those of each intervention.

Topics: Acetylcholine; Administration, Oral; Angiotensin Receptor Antagonists; Animals; Anti-Inflammatory Agents, Non-Steroidal; Antihypertensive Agents; Benzimidazoles; Biological Factors; Biphenyl Compounds; Cromakalim; Disease Models, Animal; Drug Therapy, Combination; Enalapril; Endothelium, Vascular; Enzyme Inhibitors; Hypertension; In Vitro Techniques; Indomethacin; Male; Nitroarginine; Norepinephrine; Potassium Channels; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Renin-Angiotensin System; Tetrazoles

The aim of this work was to examine whether the non-insulin-dependent diabetic Goto-Kakizaki (GK) rats develop retinal changes with similar characteristics to those observed in insulin-dependent diabetic rats in what concerns blood-retinal barrier (BRB) permeability, nitric oxide (NO) production, and retinal IL-1beta level. BRB permeability was evaluated by vitreous fluorophotometry. NO synthase (NOS) activity was assessed by the production of l-[(3)H]-citrulline and retinal IL-1beta level was determined by ELISA. The expression of the inducible isoform of NOS (iNOS) protein was evaluated by Western blot analysis and immunohistochemistry. The in vivo studies indicated that in GK rats the BRB permeability to fluorescein was increased (787.81 +/- 68 min(-1)) in comparison to that in normal Wistar rats (646.6 +/- 55 min(-1)). The ex vivo studies showed that in retinas from GK rats the NOS activity was higher (207 +/- 28.9 pmol l-[(3)H]-citrulline/mg protein/30 min) than that in normal Wistar rats (125 +/- 32.3 pmol l-[(3)H]-citrulline/mg protein/30 min). These results were correlated with an increase in the protein level of iNOS in the retinas of GK rats, which was confirmed not only by the study of the iNOS protein expression but also by the use of NOS activity inhibitors. Indeed, the data about the effect of specific inhibitors on the NOS activity revealed that in retinas from GK rats the most effective inhibitor was aminoguanidine, which predominantly inhibits the iNOS isoform whereas in retinas from normal Wistar rats it was N(G) nitro l-arginine that predominantly inhibits the constitutive isoforms of NOS. In summary, in retinas from GK rats there is an increased production of NO which may contribute to the BRB breakdown.

Topics: Animals; Arginine; Blood Glucose; Blood-Retinal Barrier; Blotting, Western; Densitometry; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diabetic Retinopathy; Disease Models, Animal; Fluorescein Angiography; Guanidines; Immunohistochemistry; Interleukin-1; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Rats; Rats, Inbred Strains; Rats, Wistar; Retina; Retinal Vessels

To investigate the effect of endogenous nitric oxide (NO) on acute necrosis pancreatitis in rats and its relation to sulfhydryl compounds and lipid peroxidation.. Acute necrosis pancreatitis in rats was induced by retrograde sodium taurocholate (5%) infusion into the pancreatobiliary duct (1 ml/kg body weight), and N(G)-nitro-L-arginine (L-NNA) was used as the inhibitor of endogenous NO. The effect of endogenous NO on pancreatic injury, serum amylase level, the pancreatic tissue levels of sulfhydryl compounds, and malonaldehyde (MDA, the end product of lipid peroxidation) was evaluated, respectively.. Sodium taurocholate administration induced evident pancreatic tissue edema and acinar necrosis, and intrapancreatic hemorrhage occurred in 2/7 rats. Both serum amylase and tissue MDA [(1.25 +/- 0.28) nmol/mg x pr vs. (0.5 +/- 0.03) nmol/mg x pr, P < 0.05] were significantly increased, but tissue sulfhydryl compounds were decreased markedly. Pretreatment with the NO inhibitor, L-NNA (12.5 mg/kg body weight), significantly intensified acinar necrosis and increased the intrapancreatic hemorrhage (10/12). L-NNA also resulted in a further increase of serum amylase and tissue MDA [(3.0 +/- 0.40) vs. (1.25 +/- 0.28) nmol/mg x pr, P < 0.05], but it had no effect on the tissue sulfhydryl compounds.. Endogenous NO has the effect of pancreatic protection, and its antioxidation may be responsible, at least in part, for the protective mechanisms. Sulfhydryl compounds may not be involved in NO's pancreatic protection mechanisms.

Topics: Amylases; Animals; Disease Models, Animal; Male; Malondialdehyde; Nitric Oxide; Nitroarginine; Pancreas; Pancreatitis, Acute Necrotizing; Rats; Rats, Wistar; Sulfhydryl Compounds; Taurocholic Acid

The onset of reperfusion and the recovery of the ERG b-wave following retinal ischemia was examined among three groups of rats: group 1 (n = 12) and group 2 (n = 6) received pretreatment with NG-nitro-L-arginine (20 mg/kg, i.p., 2 h before ischemia) followed by intravenous injection of saline (group 1) or of 200 mg/kg L-arginine (group 2) 5 min before the end of ischemia; group 3 (n = 7) received saline pretreatment followed by intravenous injection of saline as a control. Group 1 showed delayed onset of reperfusion compared to the other two groups and a reduction in the rate of the b-wave recovery compared to the control on the 1st day after reperfusion (group 1 vs. group 3; p = 0.0357). The L-arginine posttreatment significantly increased the b-wave recovery (group 2 vs. group 1; p = 0.0005 on day 1 and p < 0.0006 on day 3). The rate of the b-wave recovery in group 1 was inversely proportional to the time to establish complete reperfusion. Inhibition of nitric oxide synthase during the initial phase of reperfusion may worsen the recovery of the b-wave following retinal ischemia, at least in part, by inhibiting establishment of reperfusion.

Topics: Animals; Disease Models, Animal; Electroretinography; Enzyme Inhibitors; Ischemia; Male; Microcirculation; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Reperfusion; Retinal Diseases; Retinal Vessels; Treatment Outcome

Systemic and especially splanchnic arterial vasodilation accompany chronic portal hypertension. Different soluble mediators causing this vasodilation have been proposed, the strongest evidence being for nitric oxide (NO). No data exist if structural vascular changes may partly account for this vasodilatory state. Here, we developed a new in vivo quantitative angiogenesis assay in the abdominal cavity and determined if: 1) portal hypertensive rats show increased angiogenesis; and 2) angiogenesis is altered by inhibiting NO formation. Portal hypertension was induced by partial portal vein ligation (PVL). Sham-operated rats served as controls (CON). During the index operation (day 0), a teflon ring filled with collagen I (Vitrogen 100) was sutured in the mesenteric cavity. After 16 days, rings were explanted, embedded in paraffin, and ingrown vessels counted using a morphometry system. The role of NO was tested by adding an antagonist of NO formation (Nomega-nitro-L-arginine [NNA], 3.3 mg/kg/d) into the drinking water. The mean number of ingrown vessels per implant was significantly higher in PVL rats compared with CON rats, i.e., 1,453 +/- 187 versus 888 +/- 116, respectively (P <.05; N = 5 per group). NNA significantly (P <.01) inhibited angiogenesis in PVL (202 +/- 124; N = 5) and in CON (174 +/- 25; N = 6) rats, respectively. In contrast, the beta-adrenergic blocker, propranolol, did not prevent angiogenesis either in PVL or CON rats in a separate set of experiments (data not shown). The conclusions drawn from this study are that: 1) rats with portal hypertension show increased angiogenesis; and 2) inhibition of NO formation significantly prevents angiogenesis in both PVL and CON rats. Therefore, splanchnic vasodilation in chronic portal hypertension may also be a result of structural changes.

Topics: Adrenergic beta-Antagonists; Animals; Body Weight; Disease Models, Animal; Hypertension, Portal; Image Processing, Computer-Assisted; Implants, Experimental; Male; Neovascularization, Pathologic; Nitric Oxide; Nitroarginine; Propranolol; Rats; Rats, Sprague-Dawley

An enhanced peripheral chemoreflex has been documented in patients with chronic heart failure (CHF). This study aimed to examine the characteristics of carotid body (CB) chemoreceptors in response to isocapnic hypoxia in a rabbit model of pacing-induced CHF and to evaluate the possible role that nitric oxide (NO) plays in the altered characteristics. The chemosensitive characteristics of the CB were evaluated by recording single-unit activity from the carotid sinus nerve in both an intact and a vascularly isolated preparation. It was found that the baseline discharge under normoxia (intact preparation: arterial PO2 90-95 Torr; isolated preparation: PO2 100-110 Torr) and the chemosensitivity in response to graded hypoxia (PO2 40-70 Torr) were enhanced in CHF vs. sham rabbits. These alterations were independent of the CB preparations (intact vs. isolated). NO synthase inhibition by Nomega-nitro-L-arginine increased the baseline discharge and the chemosensitivity in the intact preparation, whereas L-arginine (10(-5) M) inhibited the baseline discharge and the chemosensitivity in the isolated preparation in sham but not in CHF rabbits. S-nitroso-N-acetylpenicillamine, an NO donor, inhibited the baseline discharge and the chemosensitivity in both CB preparations in CHF rabbits but only in the isolated preparation in sham rabbits. The amount of NO produced in vitro by the CB under normoxia was less in CHF rabbits than in sham rabbits (P < 0.05). NO synthase-positive varicosities of nerve fibers within the CB were less in CHF rabbits than in sham rabbits (P < 0.05). These data indicate that an enhanced input from CB occurs in the rabbit model of pacing-induced CHF and that an impairment of NO production may contribute to this alteration.

Topics: Animals; Arginine; Carbon Dioxide; Cardiac Pacing, Artificial; Carotid Body; Chemoreceptor Cells; Disease Models, Animal; Heart Failure; Hypoxia; Male; Nitric Oxide Synthase; Nitroarginine; Oxygen; Partial Pressure; Rabbits

Free radicals have been suggested to be largely involved in the genesis of ischemic brain damage, as shown in the protective effects of alpha-phenyl-N-tert-butyl nitrone (PBN), a spin trapping agent, against ischemic cerebral injury. In the present study, the effects of PBN as well as MCI-186, a newly-developed free radical scavenger, and oxypurinol, an inhibitor of xanthine oxidase, were evaluated in a rat transient middle cerebral aretery (MCA) occlusion model to clarify the possible role of free radicals in the reperfusion injury of brain. The volume of cerebral infarction, induced by 2-h occlusion and subsequent 2-h reperfusion of MCA in Fisher-344 rats, was evaluated. The administration of PBN (100 mg/kg) and MCI-186 (100 mg/kg) just before reperfusion of MCA significantly reduced the infarction volume. In contrast, oxypurinol (100 mg/kg) failed to show any preventive effect on the infarction. These results suggest that free radical formation is involved in the cerebral damage induced by ischemia-reperfusion of MCA, and that hydroxyl radical is responsible for the reperfusion injury after transient focal brain ischemia. It is also suggested that xanthine oxidase is not a major source of free radicals.

Topics: Animals; Antipyrine; Brain; Caudate Nucleus; Cerebral Infarction; Cyclic N-Oxides; Disease Models, Animal; Edaravone; Free Radical Scavengers; Free Radicals; Hippocampus; Ischemic Attack, Transient; Male; Nitroarginine; Nitrogen Oxides; Putamen; Rats; Rats, Inbred F344; Rats, Wistar; Reperfusion Injury; Spin Labels; Superior Colliculi

The present study was designed to examine the effects of inhibition of nitric oxide synthase on cerebral energy metabolism after hypoxia-ischemia in newborn piglets. Ten 1- to 3-d-old piglets received N(omega)-nitro-L-arginine (NNLA), an inhibitor of nitric oxide synthase (NNLA-hypoxia, n = 5), or normal saline (hypoxia, n = 5) 1 h before cerebral hypoxia-ischemia. After the infusion, hypoxia-ischemia was induced by bilateral occlusion of the carotid arteries and decreasing FiO2 to 0.07 and maintained for 60 min. Thereafter, animals were resuscitated and ventilated for another 3 h. Using 1H- and 31P-magnetic resonance spectroscopy, cerebral energy metabolism was measured in vivo at 15-min intervals throughout the experiment. Phosphocreatine to inorganic phosphate ratios decreased from 2.74 +/- 0.14 to 0.74 +/- 0.36 (hypoxia group) and 2.32 +/- 0.17 to 0.18 +/- 0.10 (NNLA-hypoxia group) during hypoxia-ischemia. Thereafter, phosphocreatine to inorganic phosphate ratios returned rapidly to baseline values in the hypoxia group, but remained below baseline values in the NNLA-hypoxia group. Intracellular pH decreased during hypoxia-ischemia and returned to baseline values on reperfusion in both groups. Intracellular pH values were lower in the NNLA-hypoxia group (p < 0.001, ANOVA). Lactate was not present during the baseline period. After hypoxia-ischemia, lactate to N-acetylaspartate ratios increased to 1.34 +/- 0.28 (hypoxia group) and 2.22 +/- 0.46 (NNLA-hypoxia group). Lactate had disappeared after 3 h of reperfusion in the hypoxia group, whereas lactate to N-acetylaspartate ratios were 1.37 +/- 1.37 in the NNLA-hypoxia group. ANOVA demonstrated a significant effect of NNLA on lactate to N-acetylaspartate ratios (p < 0.001). Inhibition of nitric oxide synthase by NNLA tended to compromise cerebral energy status during and after cerebral hypoxia-ischemia in newborn piglets.

Topics: Animals; Animals, Newborn; Brain; Brain Ischemia; Cerebrovascular Circulation; Disease Models, Animal; Energy Metabolism; Enzyme Inhibitors; Hydrogen-Ion Concentration; Hypoxia, Brain; Lactic Acid; Magnetic Resonance Spectroscopy; Nitric Oxide Synthase; Nitroarginine; Phosphates; Phosphocreatine; Swine

NADPH-d (nicotinamide-adenine dinucleotide phosphate-diaphorase) neurons are thought to migrate improperly during development in the brains of schizophrenic patients. This enzyme is a nitric oxide synthase (NOS). Nitric oxide (NO) is known to affect neurodevelopmental processes in the CNS. Therefore, we hypothesized that interference of NO generation during development may produce some aspects of schizophrenia symptomatology in a rat model. In these experiments, neonatal rats were challenged with a NOS inhibitor (L-nitroarginine 1-100 mg/kg s.c.) daily on post-natal days 3-5. L-Nitroarginine (L-NoArg) treated male rats developed a hypersensitivity to amphetamine in adulthood versus vehicle treated controls, whereas female rats did not. However, L-NoArg treated female rats developed a hypersensitivity to phencyclidine (PCP) at juvenile and adult ages versus vehicle treated controls, whereas male animals did not. L-NoArg treated male rats also had deficits in pre-pulse inhibition of startle whereas adult female rats did not. The results are discussed in terms of a new neurodevelopmental model of schizophrenia and male/female differences inherent in this disease.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Enzyme Inhibitors; Female; Male; Motor Activity; NADPH Dehydrogenase; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Schizophrenia; Sex Characteristics

Bladder outlet obstruction (BOO) is associated with altered bladder structure and function. Endothelin-1 (ET-1) has mitogenic and potent contractile properties. There are two ET receptors: ET(A) and ET(B). Nitric oxide synthase (NOS) is the enzyme responsible for the synthesis of nitric oxide (NO) which is involved in smooth muscle relaxation. We investigated whether there are any changes in the density of ET-receptors and NOS in the detrusor and bladder neck in a rabbit model of BOO. Partial BOO was induced in adult male New Zealand White rabbits. Sham operated age-matched rabbits acted as controls. After six weeks the urinary bladders were excised and detrusor and bladder neck sections incubated with radioligands for ET-1, ET(A) and ET(B) receptors and with [3H]-1-NOARG (a ligand for NOS). NADPH histochemistry was also performed. BOO bladder weights were significantly increased (P = 0.002). ET-1 binding and ETA receptor binding sites were significantly increased in the BOO detrusor smooth muscle (P = 0.04, P = 0.03 respectively) and urothelium (P = 0.002, P = 0.02 respectively). ET(B) receptor binding sites were also significantly increased in the BOO detrusor smooth muscle (P = 0.04). However, there was no change in the BOO bladder neck. NOS was significantly decreased in the detrusor smooth muscle (P = 0.003) and urothelium (P = 0.0002). In the bladder neck NOS was also significantly reduced in the urothelium (P = 0.003). NADPH staining was decreased in the detrusor and bladder neck. The up-regulation of ET receptors along with the down-regulation of NOS in the detrusor may contribute to the symptoms associated with BOO. Since ET-1 has a mitogenic role, especially via its ETA receptors, the increase in ETA receptors may also be involved in detrusor hyperplasia and hypertrophy in BOO. ET antagonists may therefore have a role in the treatment of patients with BOO.

Topics: Animals; Autoradiography; Binding Sites; Disease Models, Animal; Down-Regulation; Endothelin-1; Humans; Hyperplasia; Hypertrophy; Male; Muscle, Smooth; NADPH Dehydrogenase; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Prostatic Hyperplasia; Rabbits; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Up-Regulation; Urinary Bladder Neck Obstruction

The effect of two prostaglandin biosynthesis inhibitors and their interaction with the L-arginine/nitric oxide (NO) pathway was investigated in a rat model of experimental ileus. The gastrointestinal transit was measured as the migration of Evans blue after three different operations. Indomethacin completely reversed the additional inhibition of the transit induced by mechanical stimulation of the gut. Ketorolac completely reversed the inhibition of the transit induced by the laparotomy, but had no additional effect on the inhibition induced by mechanical stimulation of the gut. Administration of indomethacin plus L-nitroarginine or L-arginine could not enhance or prevent the effect of indomethacin alone. Administration of ketorolac and L-nitroarginine completely reversed the transit after the laparotomy plus manipulation whereas ketorolac plus L-arginine had no additional effect as compared to ketorolac alone. From these findings we conclude that in addition to NO, prostaglandins are involved in the pathogenesis of postoperative ileus in the rat. However, indomethacin and ketorolac differentially affect postoperative ileus suggesting that prostaglandins are involved in different pathogenic mechanisms leading to postoperative ileus.

Topics: Animals; Disease Models, Animal; Indomethacin; Intestinal Obstruction; Ketorolac; Nitric Oxide; Nitroarginine; Postoperative Complications; Prostaglandin Antagonists; Rats; Tolmetin

Despite intense investigation, the effector of the infarct-limiting protection observed during the late phase of ischemic preconditioning (PC) remains unknown. The goal of this study was to test the hypothesis that late PC against myocardial infarction is mediated by the activity of nitric oxide synthase (NOS).. Conscious rabbits underwent a 30-minute coronary occlusion followed by 3 days of reperfusion. In group I (control group, n= 10), infarct size (tetrazolium staining) averaged 56.8+/-5.3% of the risk region, which was decreased to 27.6+/-2.5% (P<0.05) in rabbits preconditioned 24 hours earlier with a sequence of six 4-minute occlusion/4-minute reperfusion cycles (group II, n= 10). When preconditioned rabbits were given the nonselective NOS inhibitor N(omega)-nitro-L-arginine (L-NA, 13 mg/kg i.v. [group III, n=8]) or the selective iNOS inhibitor aminoguanidine (AG, 150 mg/kg SC [group V, n=7]) before the 30-minute occlusion, the protective effect of late PC was completely abrogated; that is, infarct size (59.9+/-4.5% and 65.8+/-3.3%, respectively) was similar to that measured in the control group. Measurements of systolic wall thickening (sonomicrometry) demonstrated that L-NA and AG also abolished the improved recovery of myocardial function effected by late PC in group II. When rabbits were given L-NA or AG without prior PC (group IV [n=8] and group VI [n=6], respectively), infarct size did not differ from that observed in controls (53.8+/-4.3% and 59.8+/-4.3%, respectively), demonstrating that L-NA and AG do not increase the extent of cell death in nonpreconditioned myocardium.. Taken together, these results indicate that in the conscious rabbit, the infarct-sparing effect of the late phase of ischemic PC is mediated by the activity of NOS and suggest that the specific isoform primarily responsible for this cardioprotective phenomenon is iNOS. Thus, NO appears to be a pivotal component of the pathophysiological cascade of late PC.

Topics: Analysis of Variance; Animals; Consciousness; Disease Models, Animal; Enzyme Inhibitors; Guanidines; Heart; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Myocardium; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Rabbits; Time Factors

Nitric oxide (NO), constitutively produced by endothelial nitric oxide synthase (eNOS), plays a major role in the regulation of blood pressure and vascular tone. We generated transgenic mice overexpressing bovine eNOS in the vascular wall using murine preproendothelin-1 promoter. In transgenic lineages with three to eight transgene copies, bovine eNOS-specific mRNA, protein expression in the particulate fractions, and calcium-dependent NOS activity were confirmed by RNase protection assay, immunoblotting, and L-arginine/citrulline conversion. Immunohistochemical studies revealed that eNOS protein was predominantly localized in the endothelial cells of aorta, heart, and lung. Blood pressure was significantly lower in eNOS-overexpressing mice than in control littermates. In the transgenic aorta, basal NO release (estimated by Nomega-nitro-L-arginine-induced facilitation of the contraction by prostaglandin F2alpha) and basal cGMP levels (measured by enzyme immunoassay) were significantly increased. In contrast, relaxations of transgenic aorta in response to acetylcholine and sodium nitroprusside were significantly attenuated, and the reduced vascular reactivity was associated with reduced response of cGMP elevation to these agents as compared with control aortas. Thus, our novel mouse model of chronic eNOS overexpression demonstrates that, in addition to the essential role of eNOS in blood pressure regulation, tonic NO release by eNOS in the endothelium induces the reduced vascular reactivity to NO-mediated vasodilators, providing several insights into the pathogenesis of nitrate tolerance.

Topics: Animals; Aorta; Blood Pressure; Cattle; Cyclic GMP; Disease Models, Animal; Gene Expression Regulation; Hypotension; Immunohistochemistry; Lung; Mice; Mice, Transgenic; Muscle Contraction; Muscle Relaxation; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Phenotype; Promoter Regions, Genetic; RNA, Messenger; Vasodilation

To evaluate the effect of treatment with a combination of nitric oxide synthase inhibitors and inhaled nitric oxide on systemic hypotension during sepsis.. Prospective, randomized, controlled study on anesthetized animals.. A cardiopulmonary research laboratory.. Forty-seven male adult Sprague-Dawley rats.. Animals were anesthetized, mechanically ventilated with room air, and randomized into six groups: a) the control group (C, n=6) received normal saline infusion; b) the endotoxin-treated group received 100 mg/kg i.v. of Escherichia coli lipopolysaccharide (LPS, n=9); c) the third group received LPS, and 1 hr later the animals were treated with 100 mg/kg i.v. Nw-nitro-L-arginine (LNA, n=9); d) the fourth group received LPS, and after 1 hr, the animals were treated with 100 mg/kg i.v. aminoguanidine (AG, n=9); e) the fifth group received LPS and 1 hr later was treated with LNA plus 1 ppm inhaled nitric oxide (LNA+NO, n=7); f) the sixth group received LPS and 1 hr later was treated with aminoguanidine plus inhaled NO (AG+NO, n=7). Inhaled NO was administered continuously until the end of the experiment.. Systemic mean blood pressure (MAP) was monitored through a catheter in the carotid artery. Mean exhaled NO (ENO) was measured before LPS (T0) and every 30 mins thereafter for 5 hrs. Arterial blood gases and pH were measured every 30 mins for the first 2 hrs and then every hour. No attempt was made to regulate the animal body temperature. All the rats became equally hypothermic (28.9+/-1.2 degrees C [SEM]) at the end of the experiment. In the control group, blood pressure and pH remained stable for the duration of the experiment, however, ENO increased gradually from 1.3+/-0.7 to 17.6+/-3.1 ppb after 5 hrs (p< .05). In the LPS treated rats, MAP decreased in the first 30 mins and then remained stable for 5 hrs. The decrease in MAP was associated with a gradual increase in ENO, which was significant after 180 mins (58.9+/-16.6 ppb) and reached 95.3+/-27.5 ppb after 5 hrs (p< .05). LNA and AG prevented the increase in ENO after LPS to the level in the control group. AG caused a partial reversal of systemic hypotension, which lasted for the duration of the experiment. LNA reversed systemic hypotension almost completely but only transiently for 1 hr, and caused severe metabolic acidosis in all animals. The co-administration of NO with AG had no added benefits on MAP and pH. In contrast, NO inhalation increased the duration of the reversal in MAP after LNA, alleviated the degree of acidosis, and decreased the mortality rate (from 55% to 29%).. In this animal model, LPS-induced hypotension was alleviated slightly and durably after AG, but only transiently after LNA. Furthermore, co-administration of NO with AG had no added benefits but alleviated the severity of metabolic acidosis and mortality after LNA. We conclude that nitric oxide synthase (NOS) inhibitors, given as a single large bolus in the early phase of sepsis, can exhibit some beneficial effects. Administration of inhaled NO with NOS inhibitors provided more benefits in some conditions and therefore may be a useful therapeutic combination in sepsis. NO production in sepsis does not seem to be a primary cause of systemic hypotension. Other factors are likely to have a major role.

Topics: Administration, Inhalation; Animals; Disease Models, Animal; Drug Evaluation, Preclinical; Drug Therapy, Combination; Escherichia coli Infections; Free Radical Scavengers; Guanidines; Hemodynamics; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Random Allocation; Rats; Rats, Sprague-Dawley; Shock, Septic; Time Factors

During gestation endothelium induces decreases in vascular responses to vasopressor agents but endothelium disease is followed by hypertension and enhanced vascular reactivity during preeclampsia. In a rat model of preeclampsia induced by NO synthase inhibition we study here isolated aortic contractions. From day 13 of gestation 2 groups of Wistar female rats were fed control (C) or nitro-arginine enriched diets (0.063%, i.e. 30 mg/kg/d) (treated) (T). On gestational day 20 systolic blood pressure (SBP, mmHg) is measured by tail cuff method and isolated thoracic ring aorta contractions are studied after depolarisation (KCl 60 mM) or norepinephrine (cumulative concentrations 10-9 M-10-5 M). After chronic NOS inhibition, hypertension develops: SBP is 154 +/- 2.17 in T and 116 +/- 3.75 in C, p < 0.01 and significant proteinuria (mg/d) appears: T, 63.4 +/- 21.6 versus C 3.08 +/- 0.48, p < 0.01. NO synthase inhibition in treated rats impairs the depressed contractile response obtained in the presence of endothelium in control rats but addition of L-arginine suppresses the effect of nitroarginine. Taking in account our results and those described in literature it appears that L-arginine treatment could ameliorate some pathologic pregnancies.

Topics: Animals; Aorta, Thoracic; Constriction, Pathologic; Disease Models, Animal; Drug Evaluation, Preclinical; Endothelium, Vascular; Female; In Vitro Techniques; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Norepinephrine; Pre-Eclampsia; Pregnancy; Rats; Rats, Wistar; Vasoconstrictor Agents

Increased nitric oxide production has been implicated in impaired vascular responsiveness to vasoconstrictors in portal hypertension. However, there is no firm evidence concerning the involved nitric oxide synthase isoform. The present study investigated the possible contribution of one nitric oxide synthase isoform, the endothelial constitutive Ca2+-calmodulin dependent, in the overproduction of nitric oxide in portal hypertension.. Vascular responses to norepinephrine and acetylcholine were evaluated in isolated thoracic aortic rings from normal and portal vein stenosed rats.. An impaired concentration-dependent contraction to norepinephrine was observed in intact rings from portal hypertensive rats compared to controls. The hyporeactivity to norepinephrine was reversed after endothelium denudation, the inhibition of nitric oxide synthase with L-NOARG or the inhibition of calmodulin with W-7, but not after pre-incubation with indomethacin. Stimulation of intact rings with norepinephrine after the inhibition of calmodulin with calmidazolium was followed by a decreased vascular response in vessels from normal rats but not in those from portal hypertensive rats. Stimulation of intact rings with norepinephrine in a Ca2+-free medium was followed by a decreased vascular response in vessels from both portal hypertensive and normal rats. No difference in vasoconstrictive responses was observed between the two groups after calmidazolium or in a Ca2+-free medium. Relaxation induced by acetylcholine in norepinephrine-precontracted rings was more marked in rings from portal hypertensive rats than in controls. No differences in the vasodilator responses were observed after relaxations had been inhibited by the removal of the endothelium, pre-incubation with L-NOARG, indomethacin, W-7 or calmidazolium and in a Ca2+-free medium.. This study demonstrates the involvement of the endothelial constitutive Ca2+-calmodulin dependent nitric oxide synthase isoform in the overproduction of nitric oxide in portal hypertension.

Topics: Animals; Aorta, Thoracic; Calcium-Calmodulin-Dependent Protein Kinases; Cyclooxygenase Inhibitors; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Hypertension, Portal; Indomethacin; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Norepinephrine; Rats; Rats, Sprague-Dawley; Sulfonamides; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

We investigated the effects of aminoguanidine, a relatively selective inhibitor of inducible nitric oxide (NO) synthase, on the systemic inflammatory response syndrome induced by platelet activating factor (PAF) and by lipopolysaccharide in rats, with emphasis on NO production in vivo. Aminoguanidine treatment improved survival rates after lipopolysaccharide challenge, whereas it aggravated the lethality caused by PAF. Lipopolysaccharide induced a marked increase in the concentrations of nitrate and nitrite in plasma compared with vehicle administration, and the increase was prevented by aminoguanidine. In contrast, PAF challenge with or without aminoguanidine did not affect the concentrations of nitrate and nitrite in plasma compared with vehicle administration. These results suggest that NO derived from inducible NO synthase is not a major participant in the systemic inflammatory response syndrome induced by PAF. Aminoguanidine is not likely to provide beneficial effects in conditions where PAF is produced and the concentrations of nitrate and nitrite in plasma are not significantly increased.

Topics: Animals; Disease Models, Animal; Enzyme Induction; Enzyme Inhibitors; Guanidines; Injections, Intravenous; Lipopolysaccharides; Male; Nitrates; Nitric Oxide Synthase; Nitrites; Nitroarginine; Platelet Activating Factor; Rats; Systemic Inflammatory Response Syndrome

The pathogenesis of Hirschsprung's disease is not well understood. The suitability of the animal model for the unknown pathogenesis of inhibitory neurotransmission in Hirschsprung's disease was investigated.. Circular smooth muscle strips from the internal anal sphincter (IAS) and distal colon (2, 6, 8, 16, and 24 mm from the anal verge) from normal and Ls/Ls mice (mice homozygous for the lethal spotting mutation that develop fetal megacolon after aganglionosis of the terminal colon) were prepared to record changes in isometric tensions in response to different agents and nonadrenergic, noncholinergic nerve stimulation by electrical field stimulation.. Bethanechol was used to produce contraction of the smooth muscle strips of distal colon to record a decrease in the tension. Conversely, the IAS smooth muscle strips developed spontaneous tone. In the normal homozygous mice, electrical field stimulation caused a biphasic response, an initial decrease followed by an after-contraction, whereas in Ls/Ls mice, the predominant response was contraction. All smooth muscle strips from normal and Ls/Ls mice produced relaxation in response to sodium nitroprusside and vasoactive intestinal polypeptide.. Ls/Ls mice may serve as an appropriate animal model to investigate the pathogenesis of the inhibitory neurotransmission in Hirschsprung's disease in the distal colon and IAS.

Topics: Anal Canal; Animals; Colon; Disease Models, Animal; Electric Stimulation; Enzyme Inhibitors; Hirschsprung Disease; Mice; Mice, Mutant Strains; Muscle Relaxation; Muscle, Smooth; Neural Inhibition; Nitric Oxide Synthase; Nitroarginine; Peptide Fragments; Reference Values; Rodent Diseases; Synaptic Transmission; Vasoactive Intestinal Peptide

The vasodilator effects of acetylcholine were examined in methoxamine-preconstricted perfused kidneys taken from rats with streptozotocin (STZ)-induced diabetes. Acetylcholine-dependent vasodilatation was significantly weaker in STZ-induced diabetic rats than in age-matched controls, and it was completely abolished by treatment with 60 mM K+ plus NG-nitro-L-arginine (L-NNA) plus methylene blue in the control rats and was significantly but not completely inhibited by these treatment in the diabetic rats. Although acetylcholine-induced vasodilation was not affected by indomethacin in control rats, it was attenuated by indomethacin in the diabetic rats. Arachidonic acid-induced vasoconstriction was slightly but significantly increased in the diabetic rats. Acetylcholine increased significantly the level of 6-keto-prostaglandin F1 alpha in the effluent from perfused kidneys from diabetic rats. These results suggest that the endothelium-dependent vasodilatation induced by acetylcholine in the renal vascular bed of age-matched control rats is due to the release of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF), whereas the vasodilatation induced by acetylcholine in the STZ-diabetic kidney also involves prostaglandin I2 as well as NO and EDHF.

Topics: 6-Ketoprostaglandin F1 alpha; Acetylcholine; Animals; Anticoagulants; Arachidonic Acids; Biological Factors; Diabetes Mellitus, Experimental; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Indomethacin; Kidney; Male; Methoxamine; Methylene Blue; Nicardipine; Nitroarginine; Nitroprusside; Rats; Rats, Wistar; Streptozocin; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

In this study we compared the circulatory effects of the arginine analogue non-specific nitric oxide synthase (NOS) inhibitor N omega-nitro-L-arginine (NNA), and the specific inducible NOS (iNOS) inhibitor S-methylisothiourea (SMT) and S-(2-aminoethyl)-isothiourea (AEST) in a hyperdynamic endotoxemic dog model. Mean arterial pressure (MAP), cardiac output (CO), and myocardial contractility (MC) were measured. A hyperdynamic circulatory response was elicited with a 2-h infusion of a total dose of 5.3 micrograms/kg E. coli endotoxin (ETX). NOS inhibitory treatment (2 mg/kg) was administrated from the 45th min of endotoxemia. ETX induced a hyperdynamic circulatory response, and a significant myocardial depression. NNA induced a prolonged, SMT a transient increase in MC, both drugs elevated MAP, but decreased CO. AEST significantly prolonged the elevation in CO, but did not affect MAP. Selective inhibition of the iNOS may be a beneficial in sepsis.

Topics: Animals; beta-Aminoethyl Isothiourea; Blood Circulation; Blood Pressure; Cardiac Output; Disease Models, Animal; Dogs; Endotoxemia; Endotoxins; Enzyme Inhibitors; Escherichia coli; Escherichia coli Infections; Hemodynamics; Isothiuronium; Myocardial Contraction; Nitric Oxide Synthase; Nitroarginine; Ventricular Function, Left; Ventricular Pressure

We examined the vascular structure and endothelium-dependent relaxation in two genetic models of hypercholesterolemia: apolipoprotein E (apoE)-knockout mice and combined apoE/LDL receptor-double-knockout mice. Intimal area was increased markedly in proximal segments of thoracic aortas from apoE/LDL receptor-knockout mice [0.13 +/- 0.03 (mean +/- SE) mm2] compared with normal (C57BL/6J) mice (0.002 +/- 0.002 mm2, P < .05). Despite intimal thickening, the vascular lumen was not smaller in the aortas of apoE/LDL receptor-knockout mice (0.52 +/- 0.03 mm2) than in normal mice (0.50 +/- 0.03 mm2). In apoE-deficient mice, intimal thickening was minimal or absent, even though the concentration of plasma cholesterol was only modestly less than that in the double-knockout mouse (14.9 +/- 1.1 vs 18.0 +/- 1.2 mmol/L, respectively, P < .05). Relaxation of the aorta was examined in vitro in vascular rings precontracted with U46619. In normal mice, acetylcholine produced relaxation, which was markedly attenuated by the nitric oxide synthase inhibitor NG-nitro-L-arginine (100 microM). Relaxation to acetylcholine and the calcium ionophore A23187 was normal in apoE-deficient mice (in which lesions were minimal) but greatly impaired in the proximal segments of thoracic aortas of apoE/LDL receptor-deficient mice, which contained atherosclerotic lesions. Vasorelaxation to nitroprusside was similar in normal and apoE-knockout mice, with modest but statistically significant impairment in atherosclerotic segments of apoE/LDL receptor-knockout mice. In distal segments of the thoracic aorta of apoE/LDL receptor-deficient mice, atherosclerotic lesions were minimal or absent, and the endothelium-dependent relaxation to acetylcholine and calcium ionophore was normal. Thus, in apoE/LDL receptor-knockout mice (a genetic model of hyperlipidemia), there is vascular remodeling with preservation of the aortic lumen despite marked intimal thickening, with impairment of endothelium-dependent relaxation to receptor- and nonreceptor-mediated agonists. Atherosclerosis may be accelerated in the apoE/LDL receptor-double-knockout mouse compared with the apoE-knockout strain alone. We speculate that other factors, such as the absence of LDL receptors, may contribute to the differences in the extent of atherosclerosis in these two models of hyperlipidemia.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Animals; Aorta, Thoracic; Aortic Diseases; Apolipoproteins E; Arteriosclerosis; Calcimycin; Calcium; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Female; Hypercholesterolemia; Ionophores; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Relaxation; Nitric Oxide Synthase; Nitroarginine; Receptors, LDL; Superoxide Dismutase; Vasoconstrictor Agents

Nitric oxide (NO) synthase inhibitor, N-nitro-L-arginine (NNLA) produced dose-dependent, long-lasting catalepsy in rats, the effect being attenuated by NO donors L-arginine and molsidomine. Catalepsy induced by haloperidol (0.4 mg/kg i.p.), D2 receptor antagonist, was reduced dose-dependently by molsidomine (10.0-100.0 mg/kg) and by L-arginine at a dose of 100.0 mg/kg. Low, non-cataleptic doses of NNLA (0.1 mg/kg) and haloperidol (0.1 mg/kg) given in combination produced a marked and long-lasting catalepsy. The results suggest that NO plays a role in NNLA-induced catalepsy as well as in catalepsy elicited by haloperidol.

Topics: Animals; Arginine; Catalepsy; Disease Models, Animal; Haloperidol; Male; Molsidomine; Nitric Oxide Synthase; Nitroarginine; Parkinson Disease; Rats; Rats, Wistar; Vasodilator Agents

The authors previously reported that in vitro treatment with N(G)-nitro L-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS), reduces aqueous humor (AH) protein and cellular infiltration in endotoxin-induced uveitis in the rat eye. The objective of the current study was to determine the role(s) of respective major forms (constitutive and inducible) of NOS by comparing the effects of relatively selective inhibitors of these NOS isozymes.. N(G)-nitro L-arginine (L-NNA), a relatively selective inhibitor for constitutive NOS (c-NOS), and N-iminoethyl L-ornithine (L-NIO), a more selective inhibitor for inducible NOS (i-NOS), were administered in vivo. Male Lewis rats were footpad injected with bacterial lipopolysaccharide (LPS, 200 microgram) and were injected intraperitoneally at 0 hours, 6 hours, or both, after LPS injection with 10 mg of NIO, NNA, or saline as a control. Nitric oxide synthase activity in the ocular tissue and AH protein and cell content were determined at various times after treatment with LPS.. After in vivo treatment, L-NIO was found to be a more potent inhibitor than L-NNA for ocular i-NOS (87% versus 43% inhibition), and L-NNA was more potent than L-NIO for ocular c-NOS (81% versus 39%). Two injections of L-NNA, one at time 0 and one 6 hours after LPS injection, inhibited the AH protein increase by 71%, but L-NIO did so by only 30%. L-NNA inhibited cellular infiltration by 86%, whereas L-NIO had no significant effect on cellular infiltration. A significant inhibition of cellular infiltration and AH protein increase also was observed with a single injection of 10 mg of L-NNA but not of L-NIO when the inhibitors were given simultaneously with LPS. Thus, reduction of uveitis symptoms correlates with the inhibition of c-NOS.. The constitutive form of NOS in ocular tissue, presumably in vascular endothelial cells, appears to play a critical role at the onset of the development of endotoxin-induced uveitis.

Topics: Animals; Aqueous Humor; Arginine; Cell Count; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Isoenzymes; Lipopolysaccharides; Male; Nitric Oxide Synthase; Nitroarginine; Ornithine; Phagocytes; Rats; Rats, Inbred Lew; Salmonella; Uveitis, Anterior

To study the role of nitric oxide in the cardiovascular response to a model of a low output syndrome.. Prospective animal study.. Animal research laboratory.. Sheep anesthetized with pentobarbital, mechanically ventilated, and monitored with pulmonary arterial and peripheral arterial catheters.. A low output state was induced by inflating a balloon-tip catheter placed in the right atrium. Cardiac index was maintained at 1 L/min/m2 throughout the experiment in three groups of sheep: a) control (n=6) b)LNNA group (pretreated with the nitric oxide synthase inhibitor N omega-nitro-L-arginine [LNNA, 100 mg/kg, iv bolus, n=6); and c) dexamethasone group (pretreated with dexamethasone (6 mg/kg, intravenous bolus, n=6). Dexamethasone is an inhibitor of the induction of nitric oxide synthase. LNNA or dexamethasone were administered 15 mins before inducing the low output state.. Hemodynamic and oxygen transport variables, and plasma lactate and pyruvate concentrations, were measured at baseline and during the next 3 hrs. For a comparable decrease in cardiac index and oxygen delivery in all groups, the LNNA group had less hypotension and a more marked increase in systemic vascular resistance as compared with the control group. Oxygen consumption and oxygen extraction were higher in the LNNA group as compared with the control group at 30 and 60 mins. Plasma lactate concentration increased significantly less in the LNNA group than in the control and the dexamethasone groups during the observation period.. Inhibition of nitric oxide synthesis during a severe low output state in sheep is associated with a better hemodynamic response, as evidenced by a greater vasoconstriction, and signs of less marked tissue hypoxia. It is likely that inhibition of nitric oxide synthesis in this model leads to an imbalance between the tonic relaxing action of nitric oxide and the influences of vasoconstrictor agents.

Topics: Analysis of Variance; Animals; Arginine; Cardiac Output, Low; Cardiovascular System; Dexamethasone; Disease Models, Animal; Nitric Oxide Synthase; Nitroarginine; Prospective Studies; Sheep; Shock, Cardiogenic

Nitric oxide (NO) produced by the induced NO synthase (NOS) enzyme has been implicated in the mechanisms of the circulatory changes that occur in the later stages of sepsis. As NO produced by the constitutive form of the enzyme is known to play a role in the regulation of normal circulation, we have performed a series of experiments to study the early circulatory effects of inhibition of NOS in a hyperdynamic endotoxemic dog model. Pentobarbital-anesthetized animals were used. Cardiac output (CO) was measured by thermodilution. Myocardial contractility (MC) was estimated from the slope of the left ventricular end-systolic pressure-diameter relationship obtained from sonomicrometer- and catheter-tip manometer signals in closed chest animals. All animals received a 15 mL/kg/h infusion of Ringer's lactate. A hyperdynamic response was elicited by a 2 h infusion of a total dose of 5.3 micrograms/kg Escherichia coli O55:B5 endotoxin (ETX). CO increased initially by about 25%, and total peripheral resistance decreased by 35%. These changes subsided in 60-90 min, after which a sustained decrease in CO occurred. MC elevated transiently by 25% after the first 30 min of ETX infusion, then decreased gradually below the control level. Administration of 2 mg/kg of the NOS inhibitor N-nitro-L-arginine (NNA) between the 45th and 55th min of the ETX infusion increased MC to the level in the control group, but accelerated the decline of the initially increased CO and caused a sustained increase in total peripheral resistance to about 50% above the control level. In normal (nonendotoxin treated) dogs, NNA also caused a similar increase in MC which, however, lasted at least 3 h. Left ventricular diameter increased in the NNA-treated groups. This increase also occurred in the endotoxin-only group but with a delay of about 2.5 h. Our results demonstrate the participation of constitutive NOS-produced NO in the early hyperdynamic response of endotoxemia. Suppression of NO is associated with increased myocardial contractility. NNA treatment may be favorable for the restoration of depressed cardiac contractility during endotoxemia, but this treatment is probably detrimental for the compensatory systemic flow (CO) increase.

Topics: Anesthesia; Animals; Blood Pressure; Cardiac Output; Disease Models, Animal; Dogs; Endotoxemia; Endotoxins; Enzyme Inhibitors; Female; Heart Rate; Heart Ventricles; Hemodynamics; Male; Myocardial Contraction; Nitric Oxide Synthase; Nitroarginine; Vascular Resistance

The effects of nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine (NNA) on seizures induced by excitatory amino acids, bicuculline, pentylenetetrazol and pilocarpine were studied in mice. NNA (10 and 40 mg kg-1, i.p.) enhanced the susceptibility to intracerebroventricular (i.c.v.) kainate (KA) which was reflected by a decrease in its convulsant dose 50% (CD50) from 0.66 nmol to 0.38 and 0.29 nmol/mouse, respectively. Also, NNA (40 mg kg-1) increased the KA-induced mortality. Conversely, NNA (40 mg kg-1) produced an anticonvulsant effect against i.c.v. glutamate whose CD50 value was significantly elevated from 0.49 mumol to 0.84 mumol/mouse. The convulsive activity of i.c.v. N-methyl-D-aspartic acid (NDMA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), and trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD) was not affected by the pretreatment with NNA (40 mg kg-1). NNA (5-40 mg kg-1) also potentiated the convulsive action of systematic KA and KA-induced mortality but (up to 40 mg kg-1) remained without effect on seizures produced by bicuculline, N-methyl-D, L-aspartic acid (NMDLA), pentylenetetrazol, and pilocarpine. Only bicuculline-produced lethality was significantly enhanced. It may be concluded that the manipulation of the NO level affects differently seizures arising from a diffuse stimulation of glutamate receptors and seizures resulting from an activation of an individual subtype of these receptors. It is noteworthy that in the majority of convulsive tests used in this study, NNA exerted no modulatory effect.

Topics: Animals; Bicuculline; Disease Models, Animal; Dose-Response Relationship, Drug; Glutamic Acid; Kainic Acid; Male; Mice; Mice, Inbred Strains; Nitroarginine; Seizures

In the central nervous system, nitric oxide (NO) is increasingly being considered as a trans-synaptic retrograde messenger, being involved for instance in cellular responses to stimulation of glutamate receptors of the NMDA subtype. Thus, compounds that modify NO production, such as NO synthase inhibitors, may provide a means of altering NMDA receptor function. The functional consequences of NO synthase inhibition are, however, complicated by the fact that NO not only serves as a messenger to activate guanylyl cyclase and so to raise cGMP in target cells in response to NMDA receptor stimulation but also to induce feedback inhibition of the NMDA receptor via a redox modulatory site on the receptor complex. This may explain the contrasting results obtained previously with NO synthase inhibitors in animal models of ischaemia and seizures. In the present study, we tried to resolve the reported discrepancies about the effects of NO synthase inhibitors in seizure models by studying such drugs at various doses in a novel model of cortical seizure threshold. In this model, the threshold for seizures in rats is determined at short time intervals by applying ramp-shaped electrical pulse-trains directly to the cerebral cortex, allowing one to determine the time course of anti- or proconvulsant drug effects in individual rats. Two NO synthase inhibitors, NG-nitro-L-arginine and NG-nitro-L-arginine methyl ester, were compared with a clinically effective antiepileptic drug, i.e. valproate.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Oxidoreductases; Analysis of Variance; Animals; Arginine; Cerebral Cortex; Disease Models, Animal; Dose-Response Relationship, Drug; Electric Stimulation; Electrodes, Implanted; Epilepsy; Female; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Seizures; Valproic Acid

Reversal of heparin anticoagulation with protamine may be associated with acute pulmonary vasoconstriction. The specific site of pulmonary vasoconstriction has not been determined. This study was designed to determine the site of protamine-induced pulmonary vasoconstriction and the role of nitric oxide (NO) after protamine injection. Pigs were anesthetized and instrumented with catheters for monitoring pulmonary arterial, systemic arterial, and central venous pressures. Pulmonary capillary pressure was estimated using the arterial occlusion concept, while left atrial pressure was estimated from the equilibrium wedge pressure. Hemodynamic measurements were made during baseline, before and after heparin (200 U/kg), at peak pressure response after protamine injection (2 mg/kg), and 10 and 30 min thereafter. In the control group, pulmonary vascular resistance (PVR) values during baseline and after heparin were identical (2.7 +/- 0.4 mm Hg.L-1.min-1). At peak protamine response (1-2 min) PVR increased to 8.0 +/- 1.6, but returned to baseline value after 10 min (2.8 +/- 0.3) and remained stable for 30 min (2.2 +/- 0.3). The increase in PVR after protamine was primarily due to an increase in venous resistance from 1.0 +/- 0.2 to 4.9 +/- 1.4 mm Hg.L-1.min-1, and a much smaller increase in arterial resistance from 1.7 +/- 0.3 to 3.4 +/- 0.6 mm Hg.L-1.min-1. A second group was treated with nitrow-L-arginine (LNA, 20 mg/kg) to inhibit NO release, and then heparin and protamine were administered as in the first group. Heparin had no effect on pressures, but protamine increased PVR by the same magnitude as in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Pressure; Cardiac Output; Central Venous Pressure; Disease Models, Animal; Female; Heparin; Hypertension, Pulmonary; Male; Nitric Oxide; Nitroarginine; Protamines; Pulmonary Artery; Pulmonary Veins; Pulmonary Wedge Pressure; Swine; Vascular Resistance; Vasoconstrictor Agents

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

The hemodynamic effects of endothelin-1 (ET-1) are mediated by at least two distinct receptors: ETa and ETb receptors. Recently, ETb receptor agonists (4 Ala ET-1 and IRL 1620) were developed. To investigate the role of ETb receptor activation on the pulmonary and systemic circulations, we studied the hemodynamic effects of intrapulmonary arterial injections of these receptor agonists in 10 intact newborn lambs. At rest, 4 Ala ET-1 (290-1,725 ng/kg) changed no hemodynamic variables. IRL 1620 (180-1,095 ng/kg) decreased mean pulmonary arterial pressure (PAP, 16.8% +/- 15.0 and 17.8% +/- 8.5, p < 0.05) and left pulmonary artery blood flow (21.6% +/- 22.1 and 33.4% +/- 27.7, p < 0.05) at the two highest doses only. During U46619-induced pulmonary hypertension, both 4 Ala ET-1 (3.2% +/- 8.0 to 15.9% +/- 6.4, p < 0.05) and IRL 1620 (8.7% +/- 6.3 to 21.9% +/- 4.1, p < 0.05) produced selective dose-dependent decreases in PAP. The decrease in mean PAP induced by 4 Ala ET-1 and IRL 1620 was attenuated by N omega-nitro-L-arginine [an inhibitor of endothelium-derived nitric oxide (EDNO) synthesis] (16.6% +/- 3.5 vs. 5.9% +/- 2.3 and 16.2% +/- 3.4 vs. 6.6% +/- 2.8, p < 0.05) and by glybenclamide (a blocker of ATP-dependent potassium channels) (18.2% +/- 7.9 vs. 7.5% +/- 8.3 and 14.7% +/- 3.6 vs. 6.3% +/- 3.2, p < 0.05). ETb receptor activation produces selective pulmonary vasodilation during pulmonary hypertension in intact newborn lambs. The vasodilating properties are mediated in part by release of ENDO and by potassium channel activation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Animals, Newborn; Arginine; Blood Pressure; Disease Models, Animal; Endothelins; Endothelium, Vascular; Glyburide; Hypertension, Pulmonary; Injections, Intra-Arterial; Nitroarginine; Peptide Fragments; Prostaglandin Endoperoxides, Synthetic; Pulmonary Artery; Pulmonary Circulation; Regional Blood Flow; Sheep; Thromboxane A2; Vascular Resistance; Vasoconstrictor Agents; Vasodilation

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

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

We examined the effect of long-term nitric oxide (NO) synthase inhibition on vascular and renal endothelin-1 levels and evaluated the antihypertensive effect of endothelin ETA receptor antagonist FR139317 ((R)2(-)[(R)-2(-)[(S)-2(-)[[1-(hexahydro-1H-azepinyl)]- carbonyl]amino-4-methyl-pentanoyl]amino-3(-)[3-(1-methyl-1H- indolyl)]propionyl]amino-3-(2-pyridyl) proprionic acid] on rats in which NO synthase was blocked. Chronic NO blockade was produced by oral administration of the NO synthase inhibitor NG-nitro-L-arginine for 4 weeks, which produced sustained hypertension. At the end of this time, there were no significant changes in aortic and renal immunoreactive-endothelin levels between NG-nitro-L-arginine-treated hypertensive rats and normotensive control rats. Intravenous injection of FR139317 (10 mg/kg), which had a sufficient hypotensive effect on deoxycorticosterone acetate-salt hypertensive rats, to NG-nitro-L-arginine-treated hypertensive rats produced only a moderate hypotensive effect, to the same degree as seen in normotensive rats. The results indicate that long-term NO synthase inhibition did not affect vascular and renal endothelin-1 levels in these rats. It seems likely that endothelin-1 and ETA receptors do not contribute to the sustained hypertension induced by NO synthesis blockade.

Topics: Administration, Oral; Analysis of Variance; Animals; Arginine; Azepines; Blood Pressure; Desoxycorticosterone; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelins; Enzyme Inhibitors; Hypertension; Indoles; Injections, Intravenous; Kidney; Male; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A

Acute and chronic administration of nitric oxide (NO) synthase (NOS) inhibitors increase mean arterial blood pressure (MAP) in rats but their hemodynamic effects in other species remain unknown. Moreover, the role of NO in the control of exercise-induced vasodilation is still debated. To answer these questions, six dogs were instrumented for the continuous measurement of cardiac output (CO, electromagnetic flow probe on the aorta), MAP (aortic catheter) and left ventricular pressure (Konigsberg gauge). Total peripheral resistance (TPR) was calculated as MAP/CO ratio and dP/dt was used as an index of cardiac inotropism. The dogs were treated from day 0 (D0) to 7 (D7) by the NOS inhibitor, N omega-nitro-L-arginine (L-NNA), 20 mg/kg/day (IV). Such a dose regimen resulted in NOS inhibition evidenced (a) in vivo by a reduction of the hypotensive responses to graded doses of acetylcholine and bradykinin, (b) ex vivo by a decrease in the relaxation of the femoral artery to acetylcholine (EC 50 = 2.2 +/- 0.6 10(-7) M after L-NNA vs 2.2 +/- 0.8 10(-8) M in controls). One month after instrumentation, the dogs being conscious, MAP measured at rest remained unchanged following one week L-NNA treatment (from 90 +/- 2 at D0 to 91 +/- 5 mmHg at D7). However, TPR increased (from 3,600 +/- 290 at D0 to 6,300 +/- 510 dyn.s.cm-5 at D7) and CO decreased (from 2.1 +/- 0.2 at D0 to 1.2 +/- 0.1 l/min at D7) (all p < 0.01), partly as the result of a marked bradycardia (from 100 +/- 7 at D0 to 60 +/- 7 beats/min at D7). L-NNA induced-increase in TPR was completely reversed by a bolus injection of nitroglycerin (10 micrograms/kg). During treadmill exercise (12 km/h), heart rate (251 +/- 9 at D0 vs 226 +/- 11 beats/min at D7), CO (6.3 +/- 0.9 at D0 vs 4.3 +/- 0.7 l/min at D7) and stroke volume remained significantly lower, and TPR significantly higher (1,662 +/- 278 at D0 vs 2,621 +/- 489 dyn.s.cm-5 at D7) after L-NNA than in the control state. Thus, NOS inhibition in resting conscious dogs by L-NNA markedly increases peripheral resistance but does not increase arterial pressure. In addition, L-NNA blunts both exercise-induced peripheral vasodilation and increase in cardiac output, despite metabolic vasodilation.

Topics: Acetylcholine; Animals; Arginine; Consciousness; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Enzyme Inhibitors; Hemodynamics; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Physical Exertion

We examined the ability of the oxygen free radical scavenger, BM 15.0639 (400 mg kg-1 day-1), to correct existing sciatic motor nerve conduction velocity and endoneurial blood flow deficits in streptozotocin-diabetic rats. Rats were treated for 1 month following 1 month of untreated diabetes. Effects of treatment in non-diabetic rats were also examined. A further experiment determined the dose-response relationship for correction of conduction velocity abnormalities by BM15.0639. Diabetes caused 20.9% and 22.7% deficits in motor conduction velocity after 1 and 2 months respectively (both P < 0.001). Rats treated with BM15.0639 after the first month of untreated diabetes had conduction velocity values that were not significantly different from those for non-diabetic controls, but were significantly elevated compared to 1 or 2 months untreated diabetes (both P < 0.001). The ED50 for correction of nerve conduction velocity was approximately 36 mg kg-1 day-1. Sciatic nutritive endoneurial blood flow was 46.5% and 50.5% decreased by 1 and 2 months diabetes respectively (both P < 0.001). This was more than corrected by BM15.0639 treatment of diabetic rats, flow being approximately 33% greater than normal (P < 0.05). In contrast, 1 month BM15.0639 treatment had no effect on blood flow or conduction velocity in non-diabetic rats. Co-treatment of BM15.0639-treated diabetic rats with the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine (10 mg kg-1 day-1) largely abolished the anti-oxidant effect on conduction velocity and blood flow. Thus, the data highlight the importance of oxygen free radical activity for the neurovascular deficits in experimental diabetes which are at least in part caused by impaired NO production or release.

Topics: Analysis of Variance; Animals; Antioxidants; Diabetes Mellitus, Experimental; Disease Models, Animal; Dose-Response Relationship, Drug; Free Radical Scavengers; Lethal Dose 50; Male; Neural Conduction; Nitric Oxide Synthase; Nitroarginine; Phenols; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Sciatic Nerve; Streptozocin

To evaluate the role of nitric oxide synthase (NOS) in endotoxin-induced uveitis (EIU).. EIU was caused in Lewis rats by injecting lipopolysaccharide (LPS) into the foot pad, and the effects of an NOS inhibitor, NG-nitro L-arginine (NA), was comparatively studied by the simultaneous administration of NA and LPS. Total NOS and inducible NOS (iNOS) activities were differentially assayed in the anterior segment of the eye in EIU with and without NA treatment. The effects of NA on EIU were also evaluated by clinical manifestation, histology, and protein concentration in the aqueous humor.. In untreated rats, there was no significant iNOS activity. With the EIU model, iNOS activity showed a marked increase in the anterior segment of the eye, reaching a maximum 9 hours after LPS injection (10,850 +/- 1,650 cpm/mg protein, mean +/- SEM). NA reduced the iNOS activity 9 hours after injection to 2,400 +/- 90 cpm/mg protein (P < 0.001). Aqueous humor protein concentration in the EIU model was 10.6 +/- 0.75 mg/ml, and the cell number was 216 +/- 12 cells/microliters. NA significantly reduced these factors to 4.25 +/- 0.48 mg/microliters for the protein concentration (P < 0.0005) and 25 +/- 6 cells/ml for the cell number (P < 0.0005). Histologic studies showed less prominent infiltration of polymorphonuclear cells in the anterior uvea than for conventional EIU.. Induction of iNOS may play a key role in the pathogenesis of EIU. Because inhibition of iNOS activity reduced the inflammatory response, suppression of NO formation may inhibit the development of EIU.

Topics: Amino Acid Oxidoreductases; Animals; Anterior Eye Segment; Aqueous Humor; Arginine; Bacterial Toxins; Disease Models, Animal; Endotoxins; Enterotoxins; Enzyme Induction; Eye Proteins; Leukocyte Count; Male; Neutrophils; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Inbred Lew; Salmonella; Uveitis, Anterior

To assess the effects of the nitric oxide synthase inhibitor NG-Nitro-L-arginine on behavioural, biochemical and histological changes following global ischaemia, the Mongolian gerbil was used. Ischaemia was induced by bilateral carotid occlusion for 5 min. NG-Nitro-L-arginine was administered i.p. at either 1 or 10 mg/kg 30 min, 6, 24, and 48 h after surgery. 5 min bilateral carotid occluded animals were hyperactive 24, 48 and 72 h after surgery. NG-Nitro-L-arginine caused some attenuation in this hyperactivity. The activity of nitric oxide synthase was increased in the cerebellum, brain stem, striatum, cerebral cortex and hippocampus of 5 min bilateral carotid occluded animals. NG-Nitro-L-arginine reversed the increase in nitric oxide synthase activity in all brain regions. Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 96 h after surgery. NG-Nitro-L-arginine significantly protected against the neuronal death of cells in the CA1 layer.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Brain Ischemia; Brain Stem; Carotid Arteries; Cell Death; Cerebellum; Cerebral Cortex; Corpus Striatum; Disease Models, Animal; Gerbillinae; Hippocampus; Male; Microscopy, Fluorescence; Motor Activity; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Paraffin Embedding; Reperfusion Injury

We examined vascular reactivity to vasoconstrictors [phenylephrine (PE), serotonin (5-HT), and high K+] and vasodilators [acetylcholine (ACh), A23187, L-arginine, and nitroglycerin (NTG)] in isolated mesenteric arterial rings from control and septic rats. Sepsis was induced by cecal ligation and puncture (CLP). A possible mechanism underlying CLP-induced alteration in vascular reactivity was also investigated with N omega-nitro-L-arginine (L-NNA 50 microM), methylene blue (MB 10 microM), and indomethacin (5 microM). In vivo, septic rats manifested two distinct hemodynamic phases, a hyperdynamic state during early (9 h after CLP) phase, followed by a hypodynamic state during late (18 h after CLP) phase. Therefore, we examined ex vivo vascular reactivity in these two phases. Results demonstrated that CLP operation caused hyporesponsiveness to contractile agents and hyperresponsiveness to vasodilator agents. After endothelium removal, most of the contractile responses were enhanced in both CLP-operated (9 and 18 h after operation) and sham-operated rats, whereas enhancement of high-K(+)-induced contraction was observed only in denuded rings from CLP 18-h rats. In addition, augmentation of relaxation induced by ACh at 9 or 18 h after CLP was abolished by N omega-nitro-L-arginine or MB but not by indomethacin. A possible mechanism responsible for alterations of vascular reactivity may be overproduction of nitric oxide (NO) which is blocked by L-NNA or MB.

Topics: Animals; Arginine; Blood Glucose; Blood Pressure; Body Temperature; Cecum; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Heart Rate; In Vitro Techniques; Indomethacin; Male; Methylene Blue; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Rats; Rats, Sprague-Dawley; Sepsis; Vascular Resistance; Vasoconstrictor Agents; Vasodilator Agents

In the vascularly isolated resting and contracting (3 Hz) canine hemidiaphragm, the hypothesis that nitric oxide (NO) is an important regulator of diaphragmatic O2 extraction was tested.. The effect of an intra-arterial infusion of an NO-synthase inhibitor NG-nitro-L-arginine (L-NA) on the critical O2 delivery (QO2c), below which O2 consumption becomes dependent on O2 supply, was assessed in two groups of animals in which either saline or L-NA (6 x 10(-4) mol/L) was infused into the phrenic artery over 20 minutes. The diaphragm was then perfused either by left femoral arterial blood (autoperfusion) or by pump perfusion with blood from the femoral artery. QO2 was reduced by stepwise hemorrhage in the autoperfusion groups and by reducing the pump rate in the pump perfusion groups.. During autoperfusion, QO2c in the saline- and L-NA-treated groups was not different (0.88 +/- 0.15 and 0.98 +/- 0.12 mL/min/100 g, respectively) for the resting diaphragm. Critical O2 extraction ratios were not different (64.5% +/- 9.9% and 67.8% +/- 6.4%, respectively). In the saline group, QO2c during 3-Hz stimulation was 5.03 +/- 0.9 mL/min/100 g. In the L-NA group, diaphragm flow was lower than the saline group, and no QO2c was found. In the pump-perfused contracting diaphragm, QO2c in both groups did not differ (3.1 +/- 0.5 and 4.05 +/- 0.65 mL/min/100 g, respectively). O2 extraction ratios at these O2 deliveries were different (63.3% +/- 5.2% and 77.4% +/- 4.3%, respectively). However, NO-synthase inhibiton had no effect on maximum diaphragmatic O2 extraction ratio.. These results indicate that NO release is an important modulator of the tone of diaphragmatic resistance vessels, but it does not appear to regulate the processes by which O2 extraction is enhanced to compensate for decreased O2 delivery.

Topics: Animals; Arginine; Diaphragm; Disease Models, Animal; Dogs; Infusions, Intra-Arterial; Muscle Tonus; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Oxygen Consumption; Vascular Resistance

We evaluated the neuroprotective effect of the nitric oxide synthesis inhibitor, NG-nitro-L-arginine in a neonatal hypoxic-ischemic rat model. Unilateral hypoxic-ischemic injury was produced in the brain of 7-d-old rats using a combination of a common carotid artery ligation and a hypoxic (8% oxygen) exposure for 2.5 h. In our experimental condition, rectal temperatures did not differ between NG-nitro-L-arginine-treated and saline-injected pups. We killed the animals 72 h later and assessed the hypoxic-ischemic brain damage histologically. NG-nitro-L-arginine (2 mg/kg) administered intraperitoneally 1.5 h before hypoxia resulted in 77% reduction of the infarcted hemispheric volume and 87% reduction of the infarcted striatal volume compared to saline injected controls. NG-nitro-L-arginine given 1.5 h before the insult also significantly prevented hypoxic-ischemic damage in the five hippocampal structures examined, dentate gyrus, CA4, CA3, CA1, and subiculum. NG-nitro-L-arginine administered immediately after hypoxia did not prevent hypoxic-ischemic brain damage. These results indicate that nitric oxide plays a key role in producing neonatal hypoxic-ischemic brain damage.

Topics: Animals; Animals, Newborn; Arginine; Brain Ischemia; Disease Models, Animal; Female; Hypoxia, Brain; Male; Nitric Oxide; Nitroarginine; Rats; Rats, Wistar; Time Factors

Topics: Acute Disease; Animals; Arginine; Cerebrovascular Circulation; Disease Models, Animal; Endothelium, Vascular; Hemodynamics; Homeostasis; Hypoxia; Infusions, Intravenous; Nitric Oxide; Nitroarginine; Oxygen Consumption; Pulmonary Circulation; Streptococcal Infections; Streptococcus agalactiae; Swine

Both atherosclerotic lesions and hypoxia alter the contractile properties of the arterial wall and, in particular, may interfere with the relaxation mechanisms dependent or not on the endothelium. The present study was designed to test the effect of severe hypoxia on the contractile behavior of the atherosclerotic rabbit aorta. Segments of aortas obtained from control, cholesterol-fed, or Watanabe hereditary hyperlipidemic rabbits were mounted in organ chambers for isometric tension recording. A change of the bath PO2 from "normoxic" conditions (95% O2-5% CO2) to "hypoxic" conditions (95% N2-5% CO2) caused relaxation in the precontracted control aortas (by approximately 85%) but a transient contraction (approximately 20% of the maximal contraction obtained with 30 mM KCl) followed by a relaxation in the precontracted atherosclerotic aortas. Both types of responses were observed in aortas contracted with aggregating platelets, 5-hydroxytryptamine (5-HT), norepinephrine, endothelin, and prostaglandin F2 alpha. The hypoxic contractions in atherosclerosis were not dependent on the presence of an intact endothelium. They could not be antagonized by blockers of alpha-adrenoceptors, 5-HT2 receptors, histamine receptors, thromboxane receptors, and muscarinic cholinoreceptors. Inhibitors of cyclooxygenase, lipoxygenase, Na+, K(+)-ATPase, and free radical scavengers or an activator of endothelium-derived relaxing factor did not significantly affect the hypoxic contraction; the absence of effect of some inhibitors of protein synthesis seems to rule out the involvement of endothelin, angiotensin II, and bradykinin. The hypoxic contraction was not influenced by omission of Ca2+ from the medium or by inhibition of Ca2+ influx but was prevented by blockade of intracellular Ca2+. The inhibitor of nitric oxide synthase (nitro-L-arginine, 100 microM) and the guanylyl cyclase inhibitor (methylene blue, 10 microM) both enhanced the initial contractile responses to 5-HT to a similar extent as hypoxia and completely prevented the hypoxic contraction in the atherosclerotic tissues. The cyclic nucleotide analogues 8-bromo-cGMP and dibutyryl cAMP also inhibited the hypoxic contraction in the atherosclerotic aorta. The cGMP levels were markedly decreased and the cAMP levels were moderately decreased in the aortas of the cholesterol-fed rabbits as compared with the control aortas. Hypoxia further decreased cGMP but not the cAMP levels in atherosclerotic aortas with and without endo

Topics: Animals; Aorta; Arginine; Arteriosclerosis; Calcium; Cell Hypoxia; Cyclic GMP; Disease Models, Animal; Endothelium, Vascular; Male; Methylene Blue; Nitric Oxide; Nitroarginine; Rabbits; Serotonin; Vasoconstriction

To study the role of nitric oxide in the hemodynamic changes of sepsis.. Prospective, randomized, controlled, intervention study.. Twenty-five sheep randomized to four groups: Group A (n = 8, nonseptic sheep) received NG-nitro L-arginine (20 mg/kg i.v.) followed 15 mins later by L-arginine (200 mg/kg i.v.); group B (n = 4, nonseptic sheep) received L-arginine followed 15 mins later by NG-nitro L-arginine; group C (n = 7, septic sheep) received NG-nitro L-arginine (20 mg/kg i.v.) alone; group D (n = 6, septic sheep) received L-arginine (200 mg/kg i.v.) followed by NG-nitro L-arginine (20 mg/kg i.v.).. Sheep were anesthetized with pentobarbital, mechanically ventilated and monitored with a pulmonary artery catheter, a peripheral artery catheter, and a Miller catheter in the left ventricle. Sepsis was induced by the intravenous administration of live Escherichia coli (1.5 x 10(9) microorganisms/kg over 30 mins), which resulted in systemic hypotension, pulmonary hypertension, high cardiac output, and hyperlactatemia. Acetylcholine was administered before and after each intervention.. In nonseptic sheep (groups A and B) NG-nitro L-arginine induced an increase in mean blood pressure (BP), pulmonary arterial pressure, and systemic and pulmonary vascular resistances, accompanied by a decrease in cardiac index and the first derivative of left ventricular pressure. L-arginine administered to normal sheep induced systemic vasodilation. In the sepsis groups (groups C and D), the increases in BP and systemic vascular resistances induced by NG-nitro L-arginine were significant but less marked than in nonseptic sheep. Pretreatment of septic sheep with L-arginine totally abolished the NG-nitro L-arginine induced increases in systemic and pulmonary vascular resistances in this group. The administration of L-arginine in these animals induced both systemic and pulmonary vasodilation. Acetylcholine-mediated vasodilation was severely impaired in sepsis. In this condition, pretreatment with L-arginine improved the response to acetylcholine.. These data support the view that nitric oxide plays a significant role in modulating systemic and pulmonary vasomotor tone in normal and septic sheep. L-arginine produced systemic vasodilation in normal sheep, whereas both systemic and pulmonary vasodilation were observed in septic animals. The impaired response to an endothelium-dependent vasodilator in sepsis was improved by the previous administration of L-arginine.

Topics: Acetylcholine; Animals; Arginine; Disease Models, Animal; Drug Evaluation, Preclinical; Escherichia coli Infections; Hemodynamics; Infusions, Intravenous; Injections, Intravenous; Nitric Oxide; Nitroarginine; Random Allocation; Sheep; Shock, Septic

Endothelium-derived relaxing factor [EDRF, nitric oxide (NO) or a NO-containing compound] influences basal tone of cerebral blood vessels and mediates vasodilation in response to several stimuli. It is not known whether EDRF also modulates responses to cerebral vasoconstrictor stimuli in vivo. Our goal was to determine whether formation of EDRF inhibits constrictor responses of large cerebral arteries to serotonin. We measured cerebral blood flow (microspheres) and pial microvascular pressure (servo null) in anesthetized rabbits and calculated resistance of large cerebral arteries. Responses to an inhibitor of NO formation, NG-nitro-L-arginine (L-NNA, 3 mg/kg i.v.), were examined. L-NNA produced an increase in resistance of large arteries and total cerebral vascular resistance of approximately 15% (p less than 0.05 for both variables) and a small decrease in cerebral blood flow (35 +/- 9 vs. 32 +/- 7 ml min-1 100 g-1, mean +/- SD, p less than 0.05). Under control conditions, infusion of serotonin (10 micrograms kg-1 min-1, into the left atrium) produced an increase in resistance of large arteries. Following treatment with L-NNA, the change in resistance of large arteries in response to serotonin was increased more than twofold (0.20 +/- 0.17 vs. 0.43 +/- 0.21 mm Hg ml-1 min 100 g, p less than 0.05). In contrast, L-NNA did not alter the increase in resistance of large arteries during hypocapnia. L-arginine inhibited the effects of L-NNA on baseline cerebral vascular resistance and on responses of large arteries to serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Pressure; Brain Ischemia; Cerebral Arteries; Disease Models, Animal; Homeostasis; Nitric Oxide; Nitroarginine; Rabbits; Regional Blood Flow; Serotonin; Serotonin Antagonists; Vasoconstriction