NO Synthase

The neuronal isoform of nitric oxide synthase (nNOS), the enzyme responsible for the production of nitric oxide in the central nervous system, represents an attractive target for the treatment of various neurodegenerative disorders. X-ray crystal structures of complexes of nNOS with two nNOS-selective inhibitors, (4S)-N-{4-amino-5-[(2-aminoethylamino]pentyl}-N'-nitroguanidine (1) and 4-N-(Nomega-nitro-l-argininyl)-trans-4-amino-l-proline amide (2), led to the discovery of a conserved structural water molecule that was hydrogen bonded between the two heme propionates and the inhibitors (Figure 2). On the basis of this observation, we hypothesized that by attaching a hydrogen bond donor group to the amide nitrogen of 2 or to the secondary amine nitrogen of 1, the inhibitor molecules could displace the structural water molecule and obtain a direct interaction with the heme cofactor. To test this hypothesis, peptidomimetic analogues 3-5, which have either an N-hydroxyl (3 and 5) or N-amino (4) donor group, were designed and synthesized. X-ray crystal structures of nNOS with inhibitors 3 and 5 bound verified that the N-hydroxyl group had, indeed, displaced the structural water molecule and provided a direct interaction with the heme propionate moiety (Figures 5 and 6). Surprisingly, in vitro activity assay results indicated that the addition of a hydroxyl group (3) only increased the potency slightly against the neuronal isoform over the parent compound (1). Rationalizations for the small increase in potency are consistent with other changes in the crystal structures. [1]

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Endothelium-derived relaxing factor (EDRF) released from cultured endothelial cells was assayed by examining changes in cyclic GMP levels of rat lung fibroblasts. N omega-nitro-L-arginine and NG-monomethyl-L-arginine inhibited basal and A23187-, ATP- and melittin-induced EDRF release, and the inhibition was prevented with L-arginine. The IC50 values of N omega-nitro-L-arginine and NG-monomethyl-L-arginine for EDRF release evoked with 1 microM A23187 were 230 nM and 16 microM, respectively. N omega-nitro-L-arginine and NG-monomethyl-L-arginine did not affect cyclic GMP accumulation in the fibroblasts with atrial natriuretic factor or sodium nitroprusside. Thus, N omega-nitro-L-arginine is 70 times more potent than NG-monomethyl-L-arginine as a specific inhibitor of EDRF formation/release. [2]

Results: N omega-nitro-L-arginine (NNA) treatment induced increases in splanchnic arterial resistance (P < 0.001) and portal-collateral resistance (P < 0.05) and a decrease in portal venous inflow (P < 0.05). Portal pressure was not changed (NS). The splenic-systemic shunting was significantly decreased from 81% +/- 5% in the placebo-treated group to 69% +/- 4% in the NNA-treated group (P < 0.05), paralleled by an insignificant reduction in the mesenteric-systemic shunting (64% +/- 7% vs. 50% +/- 6%, NS). The attenuation of portal-systemic shunting by NNA was further shown by an increase in the vascular resistance of portal-systemic collateral venous bed using an in situ portal-systemic collateral perfusion model (1.27 +/- 0.05 vs. 1.07 +/- 0.03 cm H2O.mL-1 x min-1; P < 0.001). Conclusions: The results show that in portal hypertensive rats, NNA reduces portal-systemic shunting without reducing portal pressure, suggesting that NO plays a role in the collateralization of the portal system. In addition, high flow through the portal-collateral bed is probably an important driving force that is independent of portal hypertension for the development of portal-systemic shunting in portal-hypertensive rats. [3]

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Basal mean arterial pressure and heart rate were 90.8 +/- 3.0 mm Hg and 330 +/- 6 beats/min in pregnant animals and 107.1 +/- 3.2 mm Hg and 315 +/- 7 beats/min in nonpregnant animals. Pressor responses to angiotensin II, vasopressin, and norepinephrine were attenuated in gravid animals. Infusion of N omega-nitro-L-arginine significantly and in a dose-dependent manner increased mean arterial pressure and reduced heart rate. These effects could be completely reversed by L-arginine administration. Changes in mean arterial pressure were higher during pregnancy as compared with postpartum values. N omega-nitro-L-arginine infusion potentiated pressor responses to all three vasopressors, resulting in dose-response curves that were significantly shifted to the left, making them virtually identical in pregnant and postpartum rats. [4]

Enzyme and Assay [1]
All of the NOS isoforms used are recombinant enzymes overexpressed in E. coli from different sources. Murine macrophage iNOS, rat nNOS, and bovine eNOS were expressed and isolated as reported. Nitric oxide formation from NOS was monitored by the hemoglobin capture assay at 30 °C as described previously. Briefly, a solution of nNOS or eNOS contained 10 μM L-arginine, 1.6 mM CaCl2, 11.6 μg/mL calmodulin, 100 μM DTT, 100 μM NADPH, 6.5 μM H4B, 3 mM oxyhemoglobin, and specified inhibitor concentration in 100 mM Hepes (pH 7.5) in 600 μL total volume; iNOS contained the same concentrations of cofactors, except CaCl2 and calmodulin were not added. The assay was initiated by addition of enzyme and was monitored at 401 nm on a Perkin-Elmer Lambda 10 UV-vis spectrophotometer.

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Determination of Ki Values [1]
The reversible inhibition of NOS by peptidomimetic inhibitors was studied under initial rate conditions using the hemoglobin assay as described above. The apparent Ki values were obtained by measuring percent inhibition in the presence of 10 μM L-arginine with at least four different concentrations of inhibitor. Generally, the inhibitor concentrations of two higher and two lower than 50% inhibition were used. The IC50 values were determined by linear (or logarithmic for a few cases) regression analysis of the percent inhibition data. The apparent Ki values were calculated from the IC50 values using the following inhibition equation:50 % inhibition = 100[I]/{[I] + Ki (1 +[S]/Km)} or Ki = IC50/(1 +[S]/Km). Km values for L-arginine were 1.3 μM (nNOS), 8.3 μM (iNOS), and 1.7 μM (eNOS). The selectivity of an inhibitor was defined as the ratio of the respective Ki values.

Background: Nitric oxide, a vasodilator synthesized from L-arginine by vascular endothelial cells, may play a role in the development of portal-systemic collaterals. This study investigated the effect of long-term inhibition of NO secretion on portal systemic shunting. Methods: Systemic and splanchnic hemodynamics and the degree of portal-systemic shunting were evaluated in partial portal vein-ligated rats after administration of placebo (0.9% saline) or N omega-nitro-L-arginine (NNA) (approximately 2 micrograms.kg-1 x min-1) intravenously for 6 days. [3]

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Objective: With N omega-nitro-L-arginine, a potent inhibitor of nitric oxide synthesis, we tested the hypothesis that nitric oxide plays a functional role in the blunted pressor responsiveness seen during pregnancy. Study design: A group of six pregnant rats were instrumented on the fourteenth day of gestation and studied on days 19 and 20, as well as 7 days post partum. Another group of six virgin rats were similarly prepared and used 5 days after surgery. Blood pressure and heart rate were monitored in conscious freely moving animals before and during the administration of drugs or placebo. Results were analyzed, by one-way repeated-measures analysis of variance, with Dunnett's t test, or by paired t test where applicable. [4]

[1]. Structure-based design and synthesis of N(omega)-nitro-L-arginine-containing peptidomimetics as selective inhibitors of neuronal nitric oxide synthase. Displacement of the heme structural water. J Med Chem. 2007 May 3;50(9):2089-99.
[2]. N omega-nitro-L-arginine: a potent inhibitor of endothelium-derived relaxing factor formation. Eur J Pharmacol. 1990 Feb 6;176(2):219-23.
[3]. Administration of N omega-nitro-L-arginine ameliorates portal-systemic shunting in portal-hypertensive rats. Gastroenterology. 1993 Nov;105(5):1464-70.
[4]. N omega-nitro-L-arginine, an inhibitor of nitric oxide synthesis, increases blood pressure in rats and reverses the pregnancy-induced refractoriness to vasopressor agents. Am J Obstet Gynecol. 1992 May;166(5):1560-7.

N(gamma)-nitro-L-arginine is an L-arginine derivative that is L-arginine in which the terminal nitrogen of the guanidyl group is replaced by a nitro group. It is a L-arginine derivative, a N-nitro compound, a member of guanidines and a non-proteinogenic L-alpha-amino acid.
An inhibitor of nitric oxide synthetase which has been shown to prevent glutamate toxicity. Nitroarginine has been experimentally tested for its ability to prevent ammonia toxicity and ammonia-induced alterations in brain energy and ammonia metabolites. (Neurochem Res 1995:200(4):451-6)
Nitroarginine has been reported in Trypanosoma brucei with data available.
NG-nitro-L-arginine is an amino acid derivative and nitric oxide synthase (NOS) inhibitor with potential antineoplastic and antiangiogenic activities. Upon administration, NG-nitro-L-arginine inhibits the enzyme nitric oxide synthase, thereby preventing the formation of nitric oxide (NO). By preventing NO generation, the vasodilatory effects of NO are abrogated leading to vasoconstriction, reduction in vascular permeability and an inhibition of angiogenesis. As blood flow to tumors is restricted, this may result in an inhibition of tumor cell proliferation. NO plays an important role in tumor blood flow and stimulation of angiogenesis, tumor progression, survival, migration and invasiveness.
An inhibitor of nitric oxide synthetase which has been shown to prevent glutamate toxicity. Nitroarginine has been experimentally tested for its ability to prevent ammonia toxicity and ammonia-induced alterations in brain energy and ammonia metabolites. (Neurochem Res 1995:200(4):451-6)

C6H13N5O4

219.19852

219.096

C, 32.88; H, 5.98; N, 31.95; O, 29.20

2149-70-4

440005

Solid Powder

1.7±0.1 g/cm3

462.4±55.0 °C at 760 mmHg

257 °C (dec.)(lit.)

233.5±31.5 °C

0.0±2.4 mmHg at 25°C

1.638

-0.79

4

6

6

15

261

1

C(C[C@@H](C(=O)O)N)CN=C(N)N[N+](=O)[O-]

MRAUNPAHJZDYCK-BYPYZUCNSA-N

InChI=1S/C6H13N5O4/c7-4(5(12)13)2-1-3-9-6(8)10-11(14)15/h4H,1-3,7H2,(H,12,13)(H3,8,9,10)/t4-/m0/s1

(2S)-2-amino-5-[[amino(nitramido)methylidene]amino]pentanoic acid

Nitroarginine; (+)NG Nitroarginine; N5(nitroamidino); H-Arg(NO2)-OH; 2149-70-4; L-NOARG; NG-Nitro-L-arginine; NITROARGININE; L-NNA; N-Nitro-L-arginine; N-OMEGA-NITRO-L-ARGININE; (S)-2-Amino-5-(3-nitroguanidino)pentanoic acid; NGnitroLArginine LNGNitroarginine; LNNA; LNOARG; NGNitroLarginine; NGNitroarginine; NOLA; NSC 53662; NitroLarginine; NNitroLarginine; NNitroLarginine; NitroLarginine; Nitroarginine.L Ornithine

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)