We investigated the action of NOS inhibitors on NOS in rats. Both of nitric oxide synthase inhibitors, NG-monomethyl-L-arginine (L-NMMA, 3 micrometer) or NG-nitro-L-arginine methylester (L-NAME, 30 micrometer), augmented phenylephrine (PE, 10-7 M)-induced contraction which was inhibited by acetylcholine (ACh) in rat thoracic aorta. This augmentation by L-NAME or L-NMMA was attenuated with the treatment of NO precursor, arginine. ACh, however, decreased the augmentation induced by L-NMMA, but not by L-NAME. Superoxide dismutase (SOD, 50 u/ml) potentiated an inhibitory effect of ACh on the PE (10-7 M)-induced contraction. It has been known that platelet activating factor itself induces iNOS. Platelet activating factor (PAF, 10-7 M) inhibited PE (10-7 M)-induced contraction. Pretreatment with L-NMMA (30 mM) or L-NAME (30 mM) significantly blocked the inhibitory action of PAF on PE-induced contraction. L-NMMA (100 mM) or L-NAME (100 mM) reduced nerve conduction velocity (NCV) relevant to nNOS in rat sciatic nerve. ACh attenuated the reduction of NCV by L-NMMA-, but not by L-NAME-induced reduction of NCV. These results suggest that L-NMMA and/or L-NAME have different action on three types of NOS in rats.
Acetylcholine ; Animals ; Aorta, Thoracic ; Arginine ; Neural Conduction ; NG-Nitroarginine Methyl Ester ; Nitric Oxide Synthase* ; Nitric Oxide* ; Nitroarginine ; omega-N-Methylarginine ; Phenylephrine ; Platelet Activating Factor ; Rats* ; Sciatic Nerve ; Superoxide Dismutase

Hypoxic pulmonary vasoconstriction(HPV) plays an important role in matching ventilation and perfusion, and in a homeostatic compensatory mechanism for maintaining arterial blood oxygen tension. The purpose of this study was to explore effect of hypoxia on the vascular tension and to elucidate mechanism underlying hypoxic pulmonary vasoconstriction. The ring segments of the pulmonary artery were taken from forty rabbits(2~2.5 kg, male). Each ring was attached to an isometric force transducer(Grass FT-03) and suspended in a tissue bath(37degrees C) filled with 5 ml Krebs solution, aerated with 95% O2 + 5% CO2(pH 7.4) gas mixture. During 90 minutes of equilibrium period, the Krebs solution was changed every 15 minutes and the last resting tension was adjusted to 2 gm. After precontraction of the preparations with K(+) 40 mM, the aerating gas mixture was replaced by hypoxic gas(95% N2 + 5% CO2) and changes in vascular tension of isolated pulmonary artery with(n=36) and without endothelium(n=14) were recorded for 60 minutes. HPV induced biphasic vasoactive effects. To determine the mechanism of the vasorelaxing response, the pulmonary arterial rings were pretreated with indomethacin(n=8), L-nitro(w) arginine methyl ester(L-NAME, n=l0), tetra ethyl ammonium(TEA, n=12), glybenclamide(n=l1). And also to elucidate the mechanism of the hypoxic vasoconstricting response, effects of Ca free solution and pretreatment of ryanodine on the HPV were examined. The results obtained were as follows: 1) Transient phase 1 contraction followed by long lasting(about 30 minutes) relaxation and sustained phase 2 contraction were induced by hypoxic gas(95% N2+5% CO2) in rabbit pulmonary artery. 2) In endothelium removed pulmonary artery, transient phase 1 contraction was not apparent. 3) Vasorelaxation was partially blocked by K' channel blockers(TEA, glybenclamide). 4) Indomethacin and L-NAME pretreatments did not affect on the vasorelaxing response of the HPV to hypoxia. 5) Sustained phase 2 contraction was blocked by calcium free Krebs solution. 6) Indomethacin and ryanodine pretreatments did not change the phase 1 and phase 2 vasocontsricting reponses. The results of present study suggest that hypoxia-induced phase 1 contractile response is endothelium dependent, while phase 2 contractile response is dependent on calcium influx, and that the vasorelaxant response is partially mediated by K(+) channel.
Anoxia ; Arginine ; Calcium ; Characidae ; Endothelins ; Endothelium ; Indomethacin ; NG-Nitroarginine Methyl Ester ; Oxygen ; Perfusion ; Pulmonary Artery* ; Relaxation ; Ryanodine ; Vasoconstriction* ; Vasodilation ; Ventilation

PURPOSE: This study aimed to investigate the effects of vasopressin and desmopressin on the contractile and relaxative responses of rabbit cavernosal smooth muscle. MATERIALS AND METHODS: Isometric tension studies were conducted to investigate the effects of vasopressin(10(-14)-10(-8)M) and desmopressin(10(-14)- 10(-8)M) on the contraction and relaxation responses of rabbits cavernous muscle strips in an organ bath. The effects of pretreatment with phenylephrine(10(-5)M), L-NAME(10(-5)M) and indomethacin(10(-5)M) on the contraction and relaxation responses of the vasopressin and desmopressin were also investigated. The statistics were analyzed by Student's t-test and ANOVA. RESULTS: Vasopressin contracted the strips in a dose-dependent manner, while desmopressin did not. The phenylephrine-induced contraction was dose-dependently increased by vasopressin, but it was dose-dependently relaxed by desmopressin. L-NAME pre-treatment did not block the relaxation response, but indomethacin pre-treatment did. Vasopressin- induced contraction occurred the via V(1) receptor, while desmopressin- induced relaxation occurred via the V(2) receptor. CONCLUSIONS: Vasopressin, in pathophysiological circumstances, would worsen erectile dysfunction. On the contrary, desmopressin, which may induce an endothelium-dependent relaxation of the cavernous smooth muscles, would be good for erectile function.
Baths ; Caves ; Contracts ; Deamino Arginine Vasopressin ; Erectile Dysfunction ; Indomethacin ; Male ; Muscle, Smooth ; Muscles ; NG-Nitroarginine Methyl Ester ; Rabbits ; Relaxation ; Vasopressins

BACKGROUND: Nitric oxide (NO) is involved in the transmission and modulation of nociceptive information at the peripheral, spinal cord and supraspinal levels. We conducted this experiment to assess the antinociceptive effects of a nonselective nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on the modulation of pain in rats subjected to the formalin test. METHODS: Formalin 5% was injected in the right hind paw after intraperitoneal (IP) injection of various doses of L-NAME (0.5 mg/kg, 1.5 mg/kg with and without L-arginine 100 mg/kg, 5.0 mg/kg). The number of flinches was measured. RESULTS: Formalin injected into the rat hind paw induced a biphasic nociceptive behavior. IP injected L-NAME diminished the nociceptive behaviors in a dose-dependent manner during phases 1 and 2. The concomitant injection of L-arginine reversed the antinocipetive effect of L-NAME. CONCLUSIONS: The data demonstrates that a nonselective NOS inhibitor, L-NAME, possesses antinociceptive properties in rats subjected to the formalin test, and the antinociceptive effect of L-NAME is reversed by the concomitant administration of L-arginine.
Animals ; Arginine ; Formaldehyde* ; NG-Nitroarginine Methyl Ester ; Nitric Oxide Synthase* ; Nitric Oxide* ; Pain Measurement* ; Rats* ; Spinal Cord

BACKGROUND: Propofol decreases arterial blood pressure. This has been ascribed to vasodilation and decreased cardiac output occurring separately or in combination. This study investigated the relaxant effects of propofol and the effects of L-arginine and L-NAME on the vasodilation of propofol in rat thoracic aortic rings. METHODS: Isolated aortic rings were precontracted with phenylephrine (0.01 micrometer -10 micrometer) cumulatively and 10 minutes before the precontracted phenylephrine treatment, propofol was added cumulatively (1 micrometer-10 micrometer). The effects of L-NAME and L-arginine were evaluated by applying L-NAME (10 micrometer) and L-arginine (10 micrometer) after added propofol and before precontracted phenylephrine. RESULTS: A low concentration of propofol (1 micrometer) did not reduce phenylephrine-induced contraction but a high concentration of propofol (over 10 micrometer) reduced it significantly. Propofol also relaxed rat thoracic aortic rings in an endothelium independent manner. The L-NAME and L-arginine treatment did not affect the propofol-induced relaxation. CONCLUSIONS: Propofol was shown to have a biphasic vasoactive effect on rat thoracic aorta rings. The vasodilation effect of propofol was not related to the production of nitric oxide.
Animals ; Aorta, Thoracic ; Arginine* ; Arterial Pressure ; Cardiac Output ; Endothelium ; NG-Nitroarginine Methyl Ester ; Nitric Oxide ; Phenylephrine ; Propofol* ; Rats* ; Relaxation ; Vasodilation*

The present study was aimed to explore an interaction between endothelium-derived nitric oxide (NO) and atrial natriuretic peptide (ANP) systems in normotensive and hypertensive states. Rats were made two-kidney, one clip (2K1C) hypertensive and supplemented with either N-G-nitro-L-arginine methyl ester (L-NAME, 5 mg/100 ml drinking water) or L-arginine hydrochloride (400 mg/100 ml drinking water). One group supplied with normal tap water served as control. Sham-clipped rats were also divided into the L-NAME, L-arginine, and control groups. The plasma levels and atrial contents of ANP were determined at day 28 following clipping the renal artery. In 2K1C rats, the plasma level of ANP was higher and the atrial content was lower than in the sham-clipped control. L-Arginine increased the atrial content of ANP in association with a decreased plasma ANP, whereas L-NAME significantly affected neither parameter. The increase of blood pressure in 2K1C rats was not affected by L-arginine or L-NAME. In sham-clipped rats, the plasma level of ANP was significantly increased by L-NAME along with an increase in blood pressure. On the contrary, L-arginine did not affect the blood pressure or plasma ANP. The atrial content of ANP was significantly altered neither by L-arginine nor by L-NAME. These results suggest that NO plays a tonic inhibitory role on the ANP release with concomitant increases of the atrial tissue content. In addition, hypertension is suggested to modify the release and tissue storage of ANP.
Animals ; Arginine ; Atrial Natriuretic Factor ; Blood Pressure ; Drinking ; Hypertension ; NG-Nitroarginine Methyl Ester ; Nitric Oxide* ; Plasma ; Rats* ; Renal Artery ; Water

The relationship between the hepatic ischemia/reperfusion (I/R) injury and the balance of nitric oxide/endothelins (NO/ET) was studied. The changes of the ratio of NO/ET and the hepatic injury were observed in a rat hepatic I/R model pretreated with several tool drugs. In the acute phase of hepatic I/R injury, the ratio of plasma NO/ET was reduced from 1.58 +/- 0.20 to 0.29 +/- 0.05 (P < 0.01) and the hepatic damage deteriorated. NO donor L-Arg and ET receptor antagonist TAK-044 could alleviate the hepatic I/R injury to some degree, whereas NO synthase inhibitor L-NAME aggravated the damage. It was concluded that the hepatic I/R injury might be related with the disturbance of the NO/ET balance. Regulation of this balance might have an effect on the I/R injury.
Arginine ; Endothelins/*blood ; Liver/*blood supply ; NG-Nitroarginine Methyl Ester ; Nitric Oxide/*blood ; Receptors, Endothelin/antagonists & inhibitors ; Reperfusion Injury/*blood

Injection of Freund's complete adjuvant (FCA) into peripheral tissue induces inflammatory responses with accompanying pain behaviors. Injection of FCA produced a significant mechanical allodynia over time and nitric oxide(NO) is involved in this mechanism. The role of neuropeptide Y (NPY) on allodynia induced by inflammation is still controversal. We invastigated the change of spinal NPY and nitric oxide in rats with inflammation induced by subcutaneous injection of FCA and L-NG-nitro arginine methyl ester (L-NAME) into hind paw. The results are: The number of NADPH-diaphorase positive neurons and staining intensity of area increased at ipsilateral spinal ventral/dorsal horn of inflammation model. No significant changes were found with L-NAME posttreatment. Staining intensity of NPY immunoreactive (ir) area increased at ipsilateral spinal dorsal horn after FCA injection. No significant changes were found with L-NAME posttreatment. NPY-ir and NADPH-d reactive neurons were found in Rexed III-IV lamina at spinal dorsal horn. No significant change were found on all groups. The results suggest that spinal NPY is involved in the mechanism of the development and maintenance of allodynia in a state of FCA-induced inflammaion. NO may be also involved in the regulation of the quantity of NPY in spinal cord level.
Animals ; Arginine ; Horns ; Hyperalgesia* ; Inflammation* ; Injections, Subcutaneous ; Neurons ; Neuropeptide Y* ; Neuropeptides* ; NG-Nitroarginine Methyl Ester ; Nitric Oxide* ; Rats* ; Spinal Cord*

AIMS OF STUDY: During reflex micturition, the urethral outlet remains open (relaxed) to promote urinary emptying. The mechanisms involved in the relaxation of urethral outlet is thought to be complex including nitric oxide (NO) pathway and beta-adrenergic activity. The aims of the study focused on these several issues related to the neural control of urethral outlet in vivo. MATERIALS & METHODS: Female rats weighing 200~300 gm were anesthetized wish urethane. Catheters were inserted into femoral artery for drug administration.4 two-way catheter (16 G angiocath) was inserted into the bladder for saline infusion and pressure monitoring. A separate cannula (PE 50) was placed into the urethra via external urethral meatus or proximal urethrat opening to record urethral pressure. The bladder was filled with saline at a rate of 0.1 ml/min to induce reflex micturition. Urethral pressure was recorded via cannula through which saline was infused at a rate of 0.05 ml/min. Isovolumetric bladder contraction and urethral pressure were recorded simultaneously. After an equilibration period of 30 minutes, baseline intravesical and urethral pressure were recorded for 10 minutes prior to drug administration. NG-nitro-L-arginine methylester (L-NAME, 10 to 15 mg/kilrogram, i.v.), L-arginine (150 mg/kilrogram, i.v.), propranolol (1 microM., 0.1 ml/250 mg, i.a.), and phenylephrine (1 0~100 microM, i.a.) were administrated. RESULTS: During isovolumetric bladder contraction, urethral pressure was decreased simultaneously, and then returned to the resting states in conjunction with end of the bladder contraction. After the administration of L-NAME, the magnitude of reflex urethral relaxation was decreased significantly (42.6 +/- 15.1% of the control, p<0.01), and this effect was reversed by addition of L-arginine. Administration of propranolol also inhibited urethral relaxation (66.4% of the control). Administration of L-NAME followed by propranolol almost completely abolished the urethral relaxation. Administration of phenylephrine increased the resting urethral tone (mean; 4 cmH2O) significantly, and the magnitude of urethral relaxation was decreased substantially. CONCLUSION: These RESULTS suggest that urethral relaxation is mediated by several neural factors. NO seems like to a potent mediator in a reflex relaxation of the urethral smooth muscle during micturition. Also, beta-adrenergic stimulation play an important role for urethral relaxation. alpha-adrenergic nerve discharge, contributed to contraction of urethral smooth muscle, shows inhibitory effect against the reflex urethral relaxation.
Animals ; Arginine ; Catheters ; Female ; Femoral Artery ; Humans ; Muscle, Smooth ; NG-Nitroarginine Methyl Ester ; Nitric Oxide* ; Nitroarginine ; Phenylephrine ; Propranolol ; Rats ; Reflex ; Relaxation* ; Urethane ; Urethra ; Urinary Bladder ; Urination

It has not been clear whether L-arginine plays solely a role contributing to vascular nitric oxide (NO) synthesis. To investigate the mechanisms by which L-arginine induces vasorelaxation, effects of L-arginine on the isometric tension, and tissue NOx and cyclic guanosine monophosphate (cGMP) contents were examined in the isolated rat thoracic aorta. L-Arginine induced a dose-dependent relaxation of aortic rings only with intact endothelium only. The vasorelaxation response to low concentrations of L-arginine was abolished by the pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 10-4 mol/L), whereas the relaxation caused by higher concentrations L-arginine (10-5-10-3 mol/L) was maintained and even more pronounced in the presence of L-NAME. L-Arginine did not affect the vascular tension precontracted with KCl. The vascular tissue contents of NOx/cGMP were not significantly affected by L-arginine, while they were decreased by L-NAME. L-Arginine could not completely recover the NOx/cGMP decreased by L-NAME. Methylene blue only partially antagonized the relaxation response to L-arginine. Indomethacin did not affect the L-arginine-induced vasorelaxation, whereas ouabain markedly attenuated the relaxation. It is suggested that L-arginine induces vasorelaxation not only through its contribution to NO synthesis, but also through enhancing another endothelium-dependent mechanism which is NO/cGMP-independent and cyclooxygenase- independent.
Animals ; Aorta ; Aorta, Thoracic ; Arginine* ; Endothelium ; Guanosine Monophosphate ; Indomethacin ; Methylene Blue ; NG-Nitroarginine Methyl Ester ; Nitric Oxide ; Ouabain ; Rats ; Relaxation ; Vasodilation* ; Vasodilator Agents