• The Korean Journal of Physiology and Pharmacology
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• 제2권1호
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• pp.63-68
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• 1998

Nitric oxide (NO)-mediated relaxation in vascular smooth muscle involves not only activation of guanylate cyclase but also hyperpolarization of the membrane. It has been shown that depolarization decreases the [$Ca^{2+}$] sensitivity of myosin light chain kinase in arterial smooth muscle, and nitric oxide (NO)-mediated relaxation was attenuated in this situation. However, why potassium inhibits or attenuates the action of EDRF/NO is not clear. Therefore, we investigated the magnitude of relaxation and cGMP contents using measures known to release NO, such as photorelaxation, photo activated NO-mediated relaxation, and NO-donor (SNP)-mediated relaxation in porcine coronary arterial rings in which contractile conditions were made by different degree of depolarization, i.e., contraction in response to U46619 or U46619 plus KCl. In all cases, the magnitude of relaxation was significantly greater (P＜0.05) in U46619-contracted rings than in U46619+KCl-contracted ones. Although accumulation of cGMP was evident with three measures employed in the present study, no difference was found in cGMP contents between U46619 and U46619+KCl conditions, indicating that the diminished relaxation in KCl containing solution is cGMP-independent mechanism(s). To understand this further, cytosolic $Ca^{2+}$ changes due to NO were compared in rat thoracic aorta by exploiting photoactivated NO using streptozotocin (STZ) that was contracted with either NE or KCl. Fura-3 $[Ca]_{cyt}$ signal caused by NO was small and transient in high $K^+$-, but large and sustained in NE-contracted aorta. The inhibitory potency of STZ expressed in terms of $IC_{50}$ was 5.14 and 3.88 ${\mu}M$ in NE and in high $K^+$, respectively. These results suggest that modification of the cellular mobilization of $Ca^{2+}$ rather than cGMP levels may be an important mechanism for the NO-mediated relaxation when vascular membrane is depolarized, such as atherosclerosis and hypertension.

• Journal of Ginseng Research
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• 제21권2호
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• pp.119-124
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• 1997

Chronic hypertension is associated with impaired endothelial function such as reduced synthesis/release of endothelium-derived relaxing factor(EDRF, nitric oxide) and increased synthesis/release of endothelium-derived contracting factor(EDCF) including prostaglandin endoperoxide($PGH_2$) , superoxide anion both in animals and in humans. We have previously shown that ginsenosides lower the blood pressure and enhance the release of nitric oxide(NO) from endothelial cells in the rat aorta of the normotensive rats. The aim of the present study is to examine whether in vivo treatment of spontaneously hypertensive rats(SHRs) with protopanaxatriol ginsenosides(PPT) reduces the blood pressure and improves endothelial function in the isolated thoracic aorta of SHR. In addition, the contractile response to $PGH_2$ and superoxide anion in the aorta treated with PPT was assessed. SHRs at the age of 16 weeks were savaged with PPT(30 mg/kg/ day) for 2 weeks and systolic blood pressure was measured by the tail-cuff method. Whereas blood pressure was significantly increased in SHRs by 5.4 mmHg during this period of treatment, treatment of SHRs with PPT blocked the elevation of blood pressure. Endothelium-dependent relaxation to acetylcholine was significantly increased in the PPT-treated animals. $PGH_2$- and oxygen-derived free radical-induced contractions were significantly suppressed in aortic rings without endothelium from PPT-treated SHR. These findings indicate that PPT reduces the blood pressure of SHR, which may be associated with either increase of NO release or by antagonizing superoxide anion and PGH2 in the aortic smooth muscle.

• 동의생리병리학회지
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• 제30권2호
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• pp.101-108
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• 2016

This study is conducted to investigate vasorelaxant effect of Corni Fructus(CF) on rabbit carotid artery. To determine vasorelaxant effect of CF on rabbit carotid artery, arterial sections with intact or removed endothelium were used in this organ bath study. After being contracted by phenylephrine(PE), arterial sections were treated with CF extract in a dose-dependent manner. To identity its mechanism, the contracted arterial sections by PE were pretreated with indomethacin(IM), tetraethylammonium chloride(TEA), Nω-nitro-L-arginine(L-NNA) or methylene blue(MB) and 1.0 ㎎/㎖ CF extract. We also studied to confirm the effect on influx of extracellular calcium chloride(Ca²⁺) of the CF extract in rabbit carotid artery. To measure the cytotoxicity of the CF extract, cell viability of human umbilical vein endothelial cell(HUVEC) was measured by MTT assay. Generation of nitric oxide(NO) was also measured by Griess reagent. The arterial sections with intact endothelium were relaxed significantly by CF extract, but this effect was inhibited in the arterial sections with damaged endothelium. The vasorelaxant effect was inhibited significantly when arterial sections were pretreated with IM, TEA, L-NNA, MB. In Ca²⁺-free krebs solution, increasing of arterial contraction by Ca²⁺ was also inhibited by CF significantly. The treatment of CF extract increased NO concentration in HUVEC. This study suggested that the vasorelaxant effect of CF extract would be related with endothelium derived relaxing factor(EDRF) such as NO, prostacyclin(PGI₂), endothelium derived hyperpolarization factor(EDHF).

• Journal of Chest Surgery
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• 제28권12호
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• pp.1079-1095
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• 1995

Recently endogenous digitalis-like substances were found in the blood of various cardiovascular diseases and they have been considered one of the causes of evoking hypertension. However, the mechanism of endogenous digitalis-like substances-induced hypertension is not clarified yet. Therefore, the effects of Na-K pump inhibition on the contractility of vascular smooth muscle[conduit and resistant artery were investigated, using organ bath and bioassay experiment. Aortic and carotid arterial rings[conduit artery and the branches of brachial and superior mesenteric artery[resistant artery were used to find the effect of Na-K pump inhibition. The results obtained were as followes;The magnitudes of contractions induced by norepinephrine, serotonin, or acetylcholine in all these arteries were significantly increased by the inhibition of Na-K pump. The increased contractile responses to these agonists, especially to serotonin, were much more prominant in resistant arteries. Nitroprusside-induced relaxations were attenuated by Na-K pump inhibition and there were no significant differences in the effects of Na-K pump inhibition on nitroprusside-induced relaxations of these blood vessels. Endothelium-dependent relaxation was suppressed by the inhibition of Na-K pump, especially by the administration of ouabain, and this inhibitory effect was much more prominent in the branches of superior mesenteric artery, compared with other arteries. In the branches of superior mesenteric arteries, endothelium-dependent relaxation was completely blocked by ouabain. The release of EDRF was partially suppressed by Na-K pump inhibition.From the above results, it is suggested that the hypertension due to the increase in vascular resistance can be evoked by the inhibition of Na-K pump and endogenous digitalis-like substances induce hypertension through this mechanism.

• 대한치과교정학회지
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• 제25권6호
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• pp.715-722
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• 1995

Orthodontic tooth movement in response to orthodontic force results from actions of osteoclasts and osteeoblasts in the cell level. Convincing evidence has now been provided to support the view that osteoclasts are derived from mononuclear cells that originate in the bone marrow or other hematopoietic organs and they migrate to the bones via vascular routes. Nitric oxide(NO), which accounts for the biological properties of endothelium-derived relaxing factor(EDRF), is the endogenous stimulator of soluble guanylate cylase. The discovery of the formation of nitric oxide(NO) from L-arginine in mammalian tissues and its biological roles has, in the last 7 years, thrown new light onto many areas of research. Data from experiments in vitro showed that N-metyl-L-arginine(L-NMA) and L-nitro-L- arginine(L-NAME) are competitive inhibitors of nitric oxide synthase. This study suggest that the multinucleated cells in our culture have characteristics of osteoclasts and that the potential bone cell activity of nitric oxide in vitro may be mediated in part by stimulation of marrow mononuclear cells to form osteoclast-like cells. Bone marrow cells were obtaineed from tibia of 19-days old chick embryo. After sacrifice, tibia was quickly dissected and the bone were then split to expose the medullary bone. The cells were attached for 4 hours and the nonadherent cells were collected. Marrow cells weere cultured in 96-well plate in medium 199. To examine the number of TRAP-positive multinucleated cells(MNCs), $10^{-8}\;M\;Vit=D_3$ and various concentration of L-NMA and L-NAME weere added at the beginning of cultures and with each medium change. After 7 days of culture. tartrate-resistant acid phosphatase(TRAP) staining was performed for microscopic evaluation. Cells haying more than three nuclei per cell were counted as MNCs. The obsrved results were as follows;1. 1,25-dihydroxyvitamine $D_3$ stimulated the osteoclast-like multinucleated cells in cultures of chick embryo bone marrow. 2. Nitric oxide synthase inhibitors(NOSI ; N-NMA, N-NAME) stimulated the osteoclast-like cells in cultures of chick embry bone marrow. 3. 1,25-dihydroxyvitamine$D_3$ and nitric oxide synthase inhibitors did not appear to have additive effect on the generation of TRAP-positive MNCs. These results suggest that nitric oxide synthase inhibitors may stimulate the osteoclast-like multinucleated cell formation and fusion in cultures of chick bone marrow.

• 동의생리병리학회지
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• 제16권2호
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• pp.389-396
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• 2002

In the present work, we examined the mechanism of vasorelaxant effect of scopoletin, an active constituent of Artemisia capillaris on rat thoracic descending aortic rings. Scopoletin induced a concentration-dependent relaxation in rat thoracic descending aortic rings pre-contracted with phenylephrine (EC/sub 50/ = 238.94±37.4 μM), while it was less effective in rat thoracic descending aortic rings precontracted with high potassium solution (KCI 30 mM). Vasorelaxation by scopoletin was significantly inhibited after endothelial removal, but recovered at high concentration. Pretreatment of rat thoracic descending aortic rings with N/sup G/-nitro-L-arginine (100 μM), a nitric oxide synthase inhibitor, and atropine (1 μM), a muscarinic receptor antagonist, significantly inhibited scopoletin-induced relaxation of rat thoracic descending aortic rings. Neither indomethacin (3 μM), an inhibitor of cydooxygenase, nor propranolol (1 μM), a β -adrenoceptor antagonist, modified the effect of scopoletin. The combination of N/sup G/ -nitro-L-arginine (100 μ M) and miconazole (10 μ M), an inhibitor of cytochrome P 450, did not modify the effect of scopoletin, when compared with pretreatment with N/sup G/-nitro-L-arginine(100 μM) alone. Vasorelaxant effect of scopoletin was inverted by pretreatment with diltiazem (10 μM), a Ca/sup 2+/-channel blocker, at low concentration, while restored at high concentration. Apamin (K/sub ca/-channel blocker, 1 μM), 4-aminopyridine (4-AP, K/sub v/-channel blocker, 1 mM), and tetrodotoxin (TTX, Na/sup +/-channel blocker 1 μM) potentiated the vasorelaxant effect of scopoledn, but glibendamide (K/sub ATP/-channel blocker, 10 μM), tetraetylammonium(TEA, non-selective K-channel blocker, 10 mM) did not affect the relaxation of scopoletin. Free radical scavengers (TEMPO, catalase, mannitol) did not modify vascular tone. These results suggest that nitric oxide, Ca/sup 2+/ -channels play a role in endothelium-dependent relaxations to scopoletin in rat aortas, that apamin, 4-AP, TTX but not glibenclamide, TEA potentiated relaxation to scopoletin mediated by these channels, and that free radicals do not concern to the vasorelaxant effect of scopoletin.

• Tuberculosis and Respiratory Diseases
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• 제38권3호
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• pp.270-279
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• 1991

It has been well known that the integrity of airway epithelium is important in developing of bronchial hyperreactivity or bronchial asthma. But the mechanisms underlying this nonspecific airway hyperresponsiveness are not yet determined. To evaluate the ability of guinea pig trachea to release an epithelium derived relaxing factor (EpDRF) which relax rat vascular smooth muscle, we performed the coaxial bioassay using guinea pig trachea and rat aorta. And to evaluate the nature of EpDRF we investigate the influence of methylene blue and indomethacin on the coaxial bioassay. Results were as follows. 1) Vascular smooth muscle mounted into the epithelium intact trachea which was precontracted with phenylephrine was relaxed by addition of histamine or acetylcholine. But vascular smooth muscle mounted into epithelium denuded trachea failed to be relaxed. 2) Epithelium dependent relaxation of vascular smooth muscle was not affected by pretreatment of methylene blue or indomethacin. These results strongly suggests that guinea pig tracheal epithelium releases EpDRF which is able to relax rat vascular smooth muscle. And EpDRF released by airway epithelium is not related to endothelium derived relaxing factor (EDRF) or cyclooxygenase products.