• The Korean Journal of Pharmacology
• /
• v.32 no.3
• /
• pp.389-397
• /
• 1996

Gatric mucosa is exposed to toxic, reactive oxygen species generated within the lumen. Nitric oxide protected acetaminophen-induced hepatotoxicity by maintaining glutathione homeostasis. The present study examined the role of nitric oxide in mediating hydrogen peroxide - induced damage to gastric cells. Hydrogen peroxide was generated by glucose oxidase acting on ${\beta}-D-glucose$. L-arginine, $N^G-nitro-L-arginine$ methyl ester, or $N^G-nitro-L-arginine$ were treated to the cells with glucose/glucose oxidase. Lipid peroxidation and nitrite release and cellular content of glutathione were determined. As a result, dose - dependent increase in lipid peroxide production as well as dose - dependent decrease in nitrite release and cellular glutathione content were observed in glucose/glucose oxidase - treated cells. Pretreatment of L-arginine, a substrate for nitric oxide synthase, prevented the increase of lipid peroxide production and the reduction of nitrite release as well as glutathione content. Inhibitors of nitric oxide synthase such as $N^G-nitro-L-arginine$ methyl ester and $N^G-nitro-L-arginine$ did not protect hydrogen peroxide - induced cell damage. In conclusion, nitric oxide protects gestric cells from hydrogen peroxide possibly by inhibiting lipid peroxidation and by preserving cellular glutathione stores.

• Biomolecules & Therapeutics
• /
• v.2 no.2
• /
• pp.131-135
• /
• 1994

The effect of ginsenoside (GS) from Panax ginseng on basal and nitro-L-arginine suppressed nitric oxide (NO) production was studied in rat kidney. NO production was determined by conversion to [$^{14C}$]=L-citrulline from [$^{14C}$]-L-arginine both in whole kidney and three renal segments; glomerulus, cortex excluding glomerulus (cortex-) and medulla. Nitro-L-arginine (total dose of 30 mg/kg/3 days, i.p.) significantly reduced NO production in whole kidney, which was prevented by GS pretreatment (30 mg/kg/3 days, i.p.). Relative high dose of GS (120 mg/kg/4 days, i.p..) selectively increased NO production in glomerulus and cortex-. Protein content, on wet weight basis, in cortex- and glomerular DNA content were significantly reduced by GS. Our results confirm the existence of constitutive nitric oxide synthase in kidney and it seems that target nephron segment for volume expansion due to GS'NO-mediated vasodilation and for NO production stimulated by GS is cortex including glomerulus.lus.

• Biomolecules & Therapeutics
• /
• v.6 no.3
• /
• pp.225-231
• /
• 1998

This studies were performed for investigation of mechanism on central antidiuretic action of L$_{G}$-Nitro-L-arginine (L-NOARG), nitic oxide systhase inhibitor, in dog. Antidiuretic action of L-NOARG infused into the carotid artery was not affected by renal denervation but inhibited by pretreatment with arginine, NO Precusor. Furthermore, L-NOARG inhibited the diuretic action of dopamine induced by hemodynamic development. Above results suggest that antidiuretic actions of L-NOARG mediated by endogenous substances not associated with renal nerve. Therefore, it is demonstrated that those endogenous substances might be associated with NO which mediate the diuretic action of dopamine.e.

• Biomolecules & Therapeutics
• /
• v.7 no.4
• /
• pp.315-321
• /
• 1999

Since it has been known that hypoxia increases inducible nitric oxide synthase (iNOS) gene expression through hypoxia responsive element, it was possible to establish the hypothesis that nitric oxide could be a mediator of hypoxia to inhibit Cyplal promoter activity. In order to test this hypothesis, we have undertaken the study to examine the effects of hypoxia and nitric oxide on Cyplal promoter activity in Hepa I cells. Mouse Cyplal 5'flanking DNA, 1.6 Kb was cloned into pGL3 expression vector in order to construct pmCyplal-Luc. Hepa I cells were transfected with pmCyplal-Luc and were treated with $10^{-9}$ M TCDD and nitric oxide producing agents, such as lipopolysaccharide(LPS), sodium nitroprusside (SNP). Luciferase activity of reporter gene was measured from pmCyplal-Luc transfected Hepa I cell lysate which contains 2 g total protein using luciferin as a substrate. Nitric oxide producing agents, such as lipopolysaccharide (LPS), sodium nitroprusside(SNP) showed inhibition of luciferase activity that was induced by $10^{-9}$M TCDD treatment with dose dependent manner. Concomitant treatment of 1mM $N^G$-nitro-ι-arginine with $10^{-6}$~$10^{-4}$M sodium nitro-prusside recovered luciferase activity from the TCDD induced luciferase activity that was inhibited by nitric oxide producing agents. These demonstrated that nitric oxide could be a mediator of inhibitors on dioxin induced Cyplal expression in Hepa I cells.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1998.11a
• /
• pp.141-141
• /
• 1998

In order to study the effect of nitric oxide on the regulation of mouse cyplal expression, 5' flanking DNA of mouse cytochrome P450 lal was cloned into pGL3 basic vector encoding luciferase gene. pcyplal-Luc was transfected into Hepa I cells and various chemicals were treated. Luciferase activity was stimulated 1000 folds over that of control by TCDD (2,3,7,8-tetrachloro-p-dioxin) treatment and this stimulation was dose dependent. When SNP (sodium nitroprusside) which donates nitric oxide was administrated, this stimulatory effect of TCDD on luciferase activity was decreased. And LPS (lipopolysaccharide) which is an iNOS (inducible nitric oxide synthase) inducer also decreased the stimulatory effect of TCDD on luciferase. And iNOS inhibitor N$\^$G/-nitro-ι-arginine + TCDD treatment increased the stimulation effect of TCDD and this effect was abolished when ι-arginine was added to N$\^$G/-nitro-ι-arginine + TCDD treatment. When N$\^$G/-nitro-ι-arginine was concomitantly administrated with SNP or LPS to confirm the effect of nitric oxide, the inhibitory effect of SNP or LPS was abolished. These data strongly suggest that nitric oxide might be an inhibitory regulator on the cytochrome P450 lal gene expression in Hepa cells.

• Toxicological Research
• /
• v.11 no.2
• /
• pp.303-308
• /
• 1995

Nitric oxide, a physiological transmitter, is reported to mediate cellular injury in various tissues. Its reactivity to free radical is believed to be one of the reasons for its involvement in cytotoxicity. Menadione, a representative quinone, is cytotoxic to several cell systems including isolated hepatocyte, endothelial cell and red blood cells. Its toxic mechanism is related to oxidative stress, mediated by toxic free radicals. Our previous studies demonstrated that menadione induced cell lysis and increase of oxygen consumption in platelets. It has been reported that platelets have nitric oxide producing enzyme, nitric oxide synthase. Thus, we have investigated to manifest the role of nitric oxide.in menadione-induced cytotoxicity in rat platelets. Menadione induced cytotoxicity in platelets was unaffected by $N^G$-nitro-arginine methyl ester (L-NAME), selective and competitive inhibitor of nitric oxide synthase. We also invesitgated the role of extracellular nitric oxide in menadione-induced cytotoxicity of platelets by addition with sodium nitroprusside (SNP). SNP did not affect platelet cytotoxicity by menadione. These results suggested that nitric oxide which was generated endogeneously or exogeneously might have a negligible role in menadione-induced cytotoxicity in rat platelets.

• The Korean Journal of Physiology and Pharmacology
• /
• v.2 no.4
• /
• pp.511-519
• /
• 1998

This study investigated the role of nitric oxide on the oxidative damage in gastric mucosa of rats which received ischemia/reperfusion and its relation to mucus. Nitric oxide synthesis modulators such as L-arginine and $N^G-nitro-L-arginine$ methyl ester, and sodium nitroprusside, a nitric oxide donor, were injected intraperitoneally to the rats 30 min prior to ischemia/reperfusion which was induced by clamping the celiac artery and the superior mesenteric artery for 30 min and reperfusion for 1 h. Lipid peroxide production, the contents of glutathione and mucus, and glutathione peroxidase activities of gastric mucosa were determined. Histological observation of gastric mucosa was performed by using hematoxylin-eosin staining and scanning electron microscopy. The result showed that ischemia/reperfusion increased lipid peroxide production and decreased the contents of glutathione and mucus as well as glutathione peroxidase activities of gastric mucosa. Ischemia/reperfusion induced gastric erosion and gross epithelial disruption of gastric mucosa. Pretreatment of L-arginine, a substrate for nitric oxide synthase, and sodium nitroprusside prevented ischemia/reperfusion-induced alterations of gastric mucosa. However, $N^G-nitro-$ L- arginine methyl ester, a nitric oxide synthase inhibitor, deteriorated oxidative damage induced by ischemia/reperfusion. In conclusion, nitric oxide has an antioxidant defensive role on gastric mucosa by maintaining mucus, glutathione, and glutathione peroxidase of gastric mucosa.

• Biomolecules & Therapeutics
• /
• v.2 no.2
• /
• pp.136-140
• /
• 1994

To prove the hypothesis that NO- and N $O_2$-carrying molecules potentiate photorelaxation by generating NO, investigation was carried out using isolated rabbit and human corpus cavernosum. Corporal smooth muscle, in the presence or absence of endothelium, relaxed only slightly upon ultraviolet light (366 nm) irradiation. But, NO-and/or N $O_2$-containing compounds such as streptozotocin and $N^{G}$-nitro-L-arginine methyl ester significantly (p<0.01) enhanced photorelaxation in this tissue. In addition, $N^{G}$-nitro-D-arginine methyl ester, known to lack inhibitory action on NO synthase, showed concentration-dependent potentiation of the photorelaxation. Oxygen radical generating system via copper＋ascorbic acid and guanylate cyclase inhibitor, methylene blue, significantly (p<0.05) inhibited the streptozotocin-potentiated photorelaxation. Nitrite was accumulated by photolysis of streptozotocin, $N^{G}$-nitro-L-arginine methyl ester and $N^{G}$-nitro-D-arginine methyl ester, in a concentration and exposure time dependent manner. These observations indicate that NO is a potent relaxant of rabbit and human corpus cavernosum and further support the hypothesis that NO is released by photolysis from NO- and N $O_2$-carrying molecules.lecules.

• YAKHAK HOEJI
• /
• v.50 no.1
• /
• pp.52-57
• /
• 2006

The activation of cyclin dependent kinase 4 (CDK4) is found in more than half of all human cancers. Therefore CDK4 is an attractive target for the development of a novel anticancer agent. For mass screening of CDK4 inhibitor, we set up in vitro kinase assay for CDK4 activity using a cyclin D1-CDK4 fusion protein, which is constitutively active and exhibits enhanced stability. From the screening of representative compound library of Korea Chemical Bank, we found that 7-chloro-4-nitro-benzo[1,2,5]oxadiazole 1-oxide (FBP-1248) selectively inhibited CDK4 activity in vitro by ATP competitive manner. This compound prevented the phosphorylation of retinoblatsoma tumor suppressor protein, Rb, and inhibited cell growth through cell cycle arrest. In summary, we developed an efficient assay system for CDK4 activity in vitro and identified the CDK4 inhibitory compound, FBP-1248.

• YAKHAK HOEJI
• /
• v.42 no.5
• /
• pp.519-526
• /
• 1998

This study was performed in order to investigate the effect of renal function of NG-nitro-L-arginine (L-NOARG), inhibitor of nitric oxide (NO) synthase, in dog and ra bbit. L-NOARG, when given intravenously in dogs, exhibited the decrease in urine flow (vol), renal plasma flow (RPF), osmolar clearance ($C_{osm}$) and amounts of sodium and potassium excreted in urine($E_{Na},\;E_K$). These renal functions of L-NOARG showed the same aspect in rabbit, too. L-NOARG, when administered into a renal artery, showed the same pattern as was obtained when given intravenously in both experimental and control kidney in dog. L-NOARG administered into the carotid artery showed the decrease in Vol, RPF, $E_{Na}$, in a low doses that did not show any effect when given intravenously. Above results suggest that L-NOARG produces antidiuretic action in dog and rabbit, and these antidiuretic actions may be mediated by central action.