Nw-nitro-L-arginine Methyl Ester Research Articles

Renoprotective effects of the hydroethanolic extract of Senecio serratuloides against Nw-nitro L-arginine methyl ester-induced oxidative stress in wistar rats

Background: Oxidative stress is implicated in the pathogenesis of many diseases. Proper management of oxidative stress requires antioxidants from external sources to supplement that of the body. Plants are considered as a major source of antioxidants because of their natural origin and therapeutic benefits. Objectives: This study was aimed at investigating the renoprotective and antioxidant capacity of hydroethanolic extract of Senecio serratuloides (HESS). Materials and Methods: In vitro and ex vivo antioxidant capacity of the extract was investigated. Female Wistar rats were treated with Nw-nitro L-arginine methyl ester (L-NAME) (40 mg/kg) for 4 weeks and then cotreating with L-NAME (20 mg/kg) and extract (HESS150 or HESS300 mg/kg) for 2 weeks and finally with plant extract or normal saline only for 2 weeks making a total of 8 weeks. Twenty-four-hour urine samples were collected during the study, and at the end of the study; blood and kidneys were harvested for biochemical and histological assays. Results: HESS exhibited high antiradical activity against 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radicals with IC50values of 0.1 and 0.4 mg/ml, respectively. HESS significantly (P

Role of a novel tetrodotoxin-resistant sodium channel in the nitrergic relaxation of rattlesnake corpus cavernosum

Main outcome measures Cumulative concentration-response curves were constructed for acetylcholine (ACh), sodium nitroprusside (SNP), 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo [3,4-b]pyridine-3-yl]pyrimidin-4-ylamine (BAY 41-2272), and tadalafil in CCC precontracted with phenylephrine. Relaxation induced by electrical field stimulation (EFS) was also done in the absence and presence of Nw nitroL-arginine methyl ester (L-NAME;100 μM), 1H-[1, 2, 4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 μM) and tetrodotoxin (TTX; 1 μM). Results The hemipenes consisted of two functionally concentric corpora cavernosa, one of them containing radiating bundles of smooth muscle fibers (confirmed by a-actin immunostaining). Endothelial and neural nitric oxide synthases were present in the endothelium and neural structures, respectively; whereas soluble guanylate cyclase and PDE5 were expressed in trabecular smooth muscle. ACh and SNP relaxed isolated CCC, with the relaxations being markedly reduced by L-NAME and ODQ, respectively. BAY 41-2272 and tadalafil caused sustained relaxations with potency (pEC50) values of 5.84 +0.17 and 5.10 + 0.08 (N = 3–4), respectively. In precontracted CCC, EFS caused frequency-dependent relaxations that lasted three times longer than those in mammalian CC. Although these relaxations were almost abolished by either L-NAME or ODQ, they were unaffected by TTX. In contrast, EFS-induced relaxations in marmoset CC were abolished by TTX.

Control of gonadotropin secretion in prepubertal male rats by excitatory amino acids.

The role of N-methyl-D-aspartate (NMDA) and non-NMDA receptors in the control of FSH and LH secretion was analysed in prepubertal male rats. In the first experiment 4, 8, 12, 16, 20 and 30-day-old males were decapitated 15 min after vehicle, NMDA or kainic acid (KA) administration. In the second experiment, 23-day-old males were sham-orchidectomized or orchidectomized. Orchidectomized males were or were not implanted with silastic capsules containing testosterone and were sacrificed on day 30 after injection with vehicle, NMDA (15 mg kg-1), LHRH (100 ng rat-1), NMDA plus LHRH, or MK801, a non-competitive NMDA antagonist, (1 mg kg-1). In the third experiment, 30-day-old intact males pretreated with Nw-nitro-L-arginine methyl ester (NAME) or NG-methyl-L-arginine (MA), blockers of nitric oxide (NO) synthase, were sacrificed after NMDA or KA administration. In the fourth experiment, the effects of NMDA, KA, LHRH and NAME were analysed in monolayer cultures of dispersed adenohypophyseal cells. We found that: (i) NMDA and KA stimulated LH and FSH secretion in intact males; (ii) the NMDA effect on LH secretion remained after orchidectomy; (iii) FSH and LH responses to LHRH were not affected by simultaneous NMDA administration; (iv) antagonization of NMDA receptors with MK801 reduced the LH secretion in intact and orchidectomized males and blunted the FSH response to orchidectomy; (v) the stimulatory effect of NMDA or KA on LH secretion was not affected by pretreatment with blockers of NO synthase; (vi) the in vitro LH secretion remained unchanged after administration of NMDA, KA or NAME. We conclude that NMDA and non-NMDA receptors play a physiological role in the control of the basal and post-orchidectomy secretion of gonadotropins, and that this effects is independent of changes in NO generation and does not include changes in pituitary responsiveness to LHRH.

Evidence for Mas-Mediated Bradykinin Potentiation by the Angiotensin-(1-7) Nonpeptide Mimic AVE 0991 in Normotensive Rats

We evaluated the effect of the nonpeptide mimic of angiotensin (Ang)-(1-7), AVE 0991, on the hypotensive effect of bradykinin (BK). Increasing doses of intra-arterial or intravenous BK were administered before and 30 minutes after the beginning of AVE 0991 infusion. The effect of AVE 0991 on plasma Ang-converting enzyme activity was tested using Hip-His-Leu as the substrate. The interaction of AVE 0991 with Ang-converting enzyme in vivo was tested by determining its effect on the pressor action of Ang I or Ang II. AVE 0991 produced a significant and similar potentiation of intra-arterial or intravenous bradykinin. AVE 0991 did not inhibit plasma Ang-converting enzyme activity in vitro or the pressor effect of Ang I in vivo. N(W)-nitro-l-arginine methyl ester or D-Ala(7)-Ang-(1-7) administration abolished the BK potentiating effect of AVE 0991. We further examined the BK-potentiating effect of AVE 0991, evaluating its effect on NO production in rabbit endothelial cells. The NO release was measured using the 4-amino-5-methylamino-2'-7'-difluorofluorescein diacetate. A synergistic effect of AVE 0991 and BK on NO release was observed. These results suggest that AVE 0991 potentiates bradykinin through an Ang-converting enzyme-independent, NO-dependent receptor Mas-mediated mechanism. This effect may contribute to the improvement of endothelial function by AVE 0991 in vivo.

Overexpression of regucalcin suppresses apoptotic cell death in the cloned rat hepatoma H4-II-E cells induced by a naturally occurring isothiocyanate sulforaphane

The effect of regucalcin, a regulatory protein in intracellular signaling system, on cell death and apoptosis was investigated. Sulforaphane, a naturally occurring isothiocyanate, is known to induce cell cycle arrest and apoptosis in cancer cells, although its effect has not been clarified in the cloned rat hepatoma H4-II-E cells. Hepatoma H4-II-E cells (wild-type) and stable regucalcin/pCXN2-transfected cells were cultured for 72 h in a medium containing 10% fetal bovine serum (FBS). Cells with subconfluency were changed to a medium containing either vehicle or sulforaphane (10(-7) or 10(-6) M) in the absence of FBS. After medium change, cells were cultured for 24, 48, or 72 h. The number of wild-type cells was significantly decreased in the presence of sulforaphane (10(-7) or 10(-6) M). Agarose gel electrophoresis showed the presence of low-molecular-weight deoxyribonucleic acid (DNA) fragments of adherent wild-type cells cultured with sulforaphane (10(-7) or 10(-6) M) for 24 h. Sulforaphane (10(-7) or 10(-6) M)-induced cell number and DNA fragmentation was significantly suppressed in transfectants. The effect of sulforaphane (10(-6) M) in decreasing the number of wild-type cells was significantly prevented in the presence of caspase-3 inhibitor (10(-9) M), while the presence of Nomega-nitro-L-arginine methylester (NAME), an inhibitor of nitric oxide synthase, did not prevent sulforaphane-induced death of wild-type cells. Sulforaphane (10(-6) M) did not have a significant effect on cell number of transfectants in the presence of caspase-3 inhibitor or NAME. This study demonstrates that sulforaphane induces cell death and apoptosis in the cloned rat hepatoma H4-II-E cells, and that overexpression of regucalcin suppresses sulforaphane-induced apoptotic cell death which is partly mediated through caspase-3..

Increased pressor sensitivity to chronic nitric oxide deficiency in hyperthyroid rats.

We studied the effects of a possible interaction between partial nitric oxide deficiency and thyroid hormone excess on the long-term control of blood pressure (BP) and morphological and renal variables and examined the role of the renin-angiotensin system in the increased BP of this interaction. Eight groups (n=8 each) of male Wistar rats were used: a control group; 3 groups that were treated with thyroxine (50 microg/d), Nw-nitro-L-arginine methyl ester (L-NAME; subpressor dose, 1.5 mg x kg(-1) d(-1)), or thyroxine plus L-NAME; and another 4 similarly treated groups that received losartan (20 mg x kg(-1) x d(-1)) in their drinking fluid. All treatments were maintained for 3 weeks. The time course of tail systolic BP was recorded once a week. At the end of the experimental period, we measured mean arterial pressure in conscious rats and assessed the morphological, metabolic, plasma, and renal variables. Thyroxine produced a mild BP increase from the second week of treatment and an increase in plasma angiotensin II and plasma nitrates/nitrites by the end of the study. Simultaneous administration of thyroxine and a subpressor dose of L-NAME produced a marked BP increase that reached significance from the first week of treatment. Losartan produced normotension in thyroxine-treated rats and attenuated the BP elevation in thyroxine+L-NAME-treated rats. Hyperthyroid rats showed relative renal and ventricular hypertrophy, absence of absolute left ventricular hypertrophy, and proteinuria. These alterations were not changed by losartan. We conclude that an impaired nitric oxide system might have a counterregulatory homeostatic role against the prohypertensive effects of thyroid hormone and that the renin-angiotensin system plays an important role in thyroxine+L-NAME hypertension.

In vitro, nitric oxide (NO) stimulates LH secretion and partially prevents the inhibitory effect of dopamine on PRL release.

In recent years nitric oxide (NO) has emerged as an important intra- and intercellular transmitter involved in the control of hypothalamic-pituitary axis. In order to discriminate the potential actions of NO at hypothalamic or pituitary level in the control of PRL and LH release, we have studied PRL and LH secretion by dispersed pituitary cells obtained from males, cycling and lactating females in the presence of 1) sodium nitroprusside (SNP), a NO donor; 2) cyclic guanosine monophosphate (cGMP), the second messenger for a wide range of NO actions; 3) Nw-nitro-L-arginine methyl ester (NAME), a competitive inhibitor of NO synthase (NOS) and 4) oxadialoquinoxalione (OQD) and LY 83,583, antagonists of guanylyl cyclases. We found that SNP (at doses of 100 and 500 micromol) stimulated LH and FSH release and partially blocked the inhibitory action of dopamine (50 and 100 nmol) on prolactin secretion. These effects were not mimicked by cGMP and remained in the presence of OQD and LY 83,583. NAME alone had no significant effect on hormone secretion. These results suggest that NO plays a role in the control of gonadotropins and prolactin secretion acting directly at the pituitary level and that these effects are mediated by mechanisms other than changes in cGMP levels.

DOSE-RESPONSE OF L-NAME ON INTRATHECAL NITRIC OXIDE ACTIVITY AND SPINAL CORD BLOOD FLOW DURING TRANSIENT SPINAL CORD ISCHEMIA IN THE RAT

S359 INTRODUCTION: The contribution of the increase in nitric oxide (NO) activity to the regional or whole brain ischemic injuries is widely accepted [1]. But it has been unclear whether NO activity has a correlation with spinal cord (SC) blood flow and injury level during and after SC ischemia. In this study, we tested whether lumbar intrathecal NO activity increased during transient SC ischemia and reperfusion in the rat. METHODS: After approval of the study protocol by the local ethical committee, 36 male Wistar rats were included in this study. They were divided into L10, L30, and Control (C) groups (n=12, each). Each group was further divided into NO or LD subgroups (n=6, each). In each rat anesthesia was induced by pentobarbital, 50 mg/kg, ip., and maintained by 0.7-1.5% halothane. Its trachea was intubated through tracheostomy and it was put on the artificial ventilator. PaCO2 was maintained between 35 and 40 mmHg during the study. Axial and femoral arterial pressures were continuously monitored through arterial catheter and an appropriate monitoring system. Left thoracotomy was made to place the tie around the descending aorta at T5 level to induce spinal cord ischemia. T11 through T13 laminectomy was made and dura was opened. NO subgroups were placed NO electrode intrathecally after calibration. NO activity was continuously determined by the NO meter (NO-501, Intermedical, Japan). LD subgroups were placed Laser Doppler Flow (LDF) meter (FLO-N1, Omega wave, Japan), and LDF was continuously determined L10, L30 and C groups were given Nw Nitro L-arginine methyl ester (L-NAME) (Sigma, St. Louis, U.S.A.), 10 mg/kg, 30 mg/kg, and saline, iv., respectively, 10 minutes before the 27 minutes' aortic clamp. Axial and femoral mean arterial pressure were controlled below 90 and 15 mmHg during the aortic clamp, respectively, and maintained at baseline values after declamp. NO activity changes and LDF were compared between groups at baseline, 27 min after clamp, at peak, 30 min, 60 min, and 120 min after declamp using ANOVA. P<0.05 was considered statistically significant. RESULTS: Main results were shown in Table 1.Table 1DISCUSSION: The results of this study shows that L-NAME attenuated the increase in NO activity during and after SC ischemia dose-dependently, but that blood flow was maintained in L10 group after transient SC ischemia more than the other groups.

Interactions between N-methyl-D-aspartate, nitric oxide and serotonin in the control of prolactin secretion in prepubertal male rats.

The role of N-methyl-D-aspartate (NMDA) in the control of prolactin (PRL) secretion was analysed in prepubertal male rats. In experiment 1, males of different ages were decapitated after administration of NMDA or vehicle. In experiment 2, 30-day-old males were killed at different times after administration of vehicle, NMDA, MK-801 (a non-competitive NMDA antagonist) or NMDA plus MK-801. In experiment 3, 23-day-old males were sham-orchidectomized or orchidectomized. Orchidectomized males were or were not implanted with Silastic capsules containing different amounts of testosterone. On day 30, the animals were decapitated after administration of vehicle, NMDA or MK-801. In experiment 4, 30-day-old male rats were decapitated after being injected with vehicle, NMDA, Nw-nitro-L-arginine methyl ester (NAME) (an inhibitor of nitric oxide (NO) synthase), or NMDA plus NAME. Serum PRL concentrations, and dopamine pituitary and hypothalamic content were measured. In experiment 5, males pretreated with vehicle or NAME were killed after administration of the precursor of serotonin synthesis 5-hydroxytryptophan (5-HTP), the 5-HT1 receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) or the 5-HT2 agonist (+/-) 2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI). Finally, the effects of NMDA, NAME and sodium nitroprusside (SNP) were tested in dispersed adenohypophyseal cells. We found that: (1) antagonism of NMDA receptors with MK-801 decreased PRL secretion in intact, orchidectomized and orchidectomized-testosterone treated male rats; (ii) NMDA inhibited PRL release in vivo through an increase in dopamine release and this effect was potentiated by NAME and prevented by testosterone; (iii) NMDA inhibited PRL, secretion in vitro and this effect was observed in presence of both SNP and NAME; (iv) NAME blocked the stimulatory effects of 5-HTP and DOI on PRL secretion. We conclude that endogenous glutamate stimulates PRL release and that NO might have a pivotal role in the mechanisms involved in the control of PRL release, inhibiting the release of dopamine and modulating the effects of NMDA and 5-HT.

Effects of N-methyl-D-aspartate and kainic acid on prolactin secretion in prepubertal female rats.

The control of prolactin (PRL) secretion by N-methyl-D-aspartate (NMDA) and kainic acid (KA), agonists of NMDA and kainate receptors, and the interactions between NMDA and KA with nitric oxide (NO) were analysed in prepubertal female rats. For this purpose, serum PRL concentrations and hypothalamic and pituitary dopamine (DA) and serotonin (5-HT) concentrations were measured in females injected with NMDA, KA or two blockers of NO synthase: Nw-nitro-L-arginine methyl ester (NAME) and Nw-nitro-L-arginine (NA). Also, the effects of combined administration of NMDA and KA with the blockers of NO synthase were analyzed. We found that PRL release was inhibited 15 min after NMDA and KA administration, an effect probably mediated through the release of hypothalamic DA, as shown by the higher pituitary DA concentrations after NMDA or KA administration. The inhibitory effect of NMDA was preceded by an increase in serum PRL levels, observed at 5 and 10 min after NMDA administration. Nw-Nitro-L-arginine methyl ester alone inhibited prolactin secretion, and both NAME and NA abolished the inhibitory effect of KA, but not that of NMDA. We conclude that administration of NMDA exerted a dual action on PRL secretion: initially DA release was inhibited, leading to an increase in PRL secretion that in turn stimulated DA release and decreased serum PRL concentrations. Kainic acid also inhibited PRL secretion by releasing DA, an effect blocked by NO synthase inhibitors.

Modulation of glomerular hypertension defines susceptibility to progressive glomerular injury

The fawn-hooded rat constitutes a spontaneous model for chronic renal failure with early systemic and glomerular hypertension, proteinuria (UpV) and high susceptibility to development of focal and segmental glomerular sclerosis (FGS). It has been argued that uninephrectomy (UNX) accelerates the development of glomerular injury by aggravation of glomerular hypertension and by an independent effect to promote glomerular enlargement. The present study was performed to further delineate the importance of these parameters for the development of FGS. At the age of eight weeks male rats were UNX and randomly assigned to either control (CON), enalapril (ENA) or Nw-nitro L-arginine methyl ester (NAME) treatment. In all groups glomerular hemodynamic studies were performed four weeks post-UNX. Systemic blood pressure and UpV were monitored for 4 to 12 weeks post-UNX. Kidneys were then prepared for morphologic study. ENA treatment achieved control of both systemic and glomerular hypertension, maintenance of glomerular hyperfiltration and hyperperfusion, increased ultrafiltration coefficient(Kf), and long-term protection against UpV and FGS. NAME rats showed aggravation of both systemic and glomerular hypertension, decreased renal perfusion and filtration with reduced Kf, and high filtration fraction. The incidence of FGS in NAME and CON groups was similar at 8 and 12 weeks post-UNX, respectively. Glomerular enlargement was present in CON and ENA rats, but did not correlate with injury, while glomerular tuft size was lowest in NAME rats, which displayed prominent glomerular injury. Systemic blood pressure correlated strongly with glomerular capillary pressure. We conclude that systemic and glomerular hypertension govern the development of UpV and FGS.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of Nitric Oxide (NO) production selectively impairs learning and memory in the rat

Animals administered the nitric oxide (NO) synthase inhibitor N- w-nitro-L-arginine methyl ester (NAME) for five days exhibited severe deficits in acquisition of a place-navigation learning task. The effect of NAME was selective to place-navigation learning. NAME had no effect on sensorimotor or motivational processes in a related task. These results are consistent with the view that NO participates in learning and execution of memory tasks.

Nonendothelial aortic source of nitric oxide in Wistar-Kyoto normotensive and spontaneous hypertensive rats.

Using a recognized inhibitor of nitric oxide (NO) synthesis, Nw-nitro L-arginine methyl ester (L-NAME), we tested the hypothesis of the existence of a nonendothelial source of NO in vascular tissue using rings of rat thoracic aorta in which endothelial cells have been removed by mechanical abrasion and have totally lost their endothelium-dependent relaxation. Contractility of the muscle was tested by recording the concentration-dependent contraction of the preparations induced by an alpha-adrenergic agonist, phenylephrine. Contractility in aortas from Wistar-Kyoto normotensive rats (WKY) and spontaneous hypertensive rats (SHR) was not significantly affected by a 30-min to 2-hour incubation with L-NAME prior to agonist stimulation. However, preparations incubated for 30 min with 1 mM L-arginine (L-ARG) and then washed for 1 h in standard Krebs solution had a significantly reduced contraction to phenylephrine in both WKY and SHR. In these preparations pretreated with L-ARG, L-NAME significantly increased contractility in both WKY and SHR; this effect was prevented by L-ARG but not by D-arginine. Responses to phenylephrine were not inhibited by L-ARG when preparations were incubated from the beginning of the experiment with 1 mM cycloheximide, thus suggesting a dependence on protein synthesis of the attenuation of contraction seen with L-ARG. Intact aortic rings processed for NADPH diaphorase histochemistry, a putative marker for NO synthase, showed NADPH diaphorase reactivity only in the endothelial layer and in the adventitia.(ABSTRACT TRUNCATED AT 250 WORDS)