• 동의생리병리학회지
• /
• 제21권2호
• /
• pp.408-413
• /
• 2007

Vascular tone plays an important role in the regulation of blood pressure. In the present study, the methanol extract of Rosae multiflora Radix (MRM) induced dose-dependent relaxation of phenylephrine-precontracted aorta, which was abolished by removal of functional endothelium. Pretreatment of the endothelium-intact aortic tissues with $N^G$-nitro-L-arginine methly ester (L-NAME) or 1H-[1,2,4]-oxadiazole-[4,3-${\alpha}$]-quinoxalin-1-one (ODQ) inhibited the relaxation induced by MRM, respectively. But, the relaxation effect of MRM was not blocked by indomethacine, glibenclamide, tetraethylammonium (TEA), verapamil, diltiazem, atropine, and propranolol, respectively. Moreover, incubation of endothelium-intact aortic rings with MRM increased the production of cGMP. Taken together, the present results suggest that MRM relaxes vascular smooth muscle via endothelium-dependent nitric oxide/cGMP signaling. These results would be useful for further study to MRM on animal models with cardiovascular diseases.

• Journal of Chest Surgery
• /
• 제24권3호
• /
• pp.229-244
• /
• 1991

A bioassay technique and organ bath study were performed to analyze the effects of extracellular $Ca^{2+}$ and $Ca^{2+}$-antagonists on endothelium-derived relaxing factor[s][EDRF] released from the endothelial cells of rabbit aorta. Transverse strips with intact endothelium or damaged endothelium were used for the mechanical contraction experiment using organ bath. Long segment including thoracic and abdominal aorta with endothelium [EDRF donor aorta] was perfused with Tyrode solution which was aerated with 95% $O_2-5%$ $CO_2$ mixed gas and kept at 35oC. The perfusate was bioassayed with a transverse strip of thoracic aorta with damaged endothelium. The test strip was contracted with nor-epinephrine and acetylcholine was used to stimulate the release of EDRF from endothelial cells. The results obtained were as follows; 1] The endothelium-dependent relaxation[EDR] induced by acetylcholine was biphasic; an initial rapid relaxation followed by a slow relaxation. 2] EDR induced by acetylcholine was reduced gradually with the decrease in the concentration of extracellular $Ca^{2+}$. The effect of extracellular $Ca^{2+}$ on EDR was more prominent in the late slow relaxation phase. 3] EDR to acetylcholine was not altered by acute exposure to organic $Ca^{2+}$-antagonists. Pretreatment with verapamil to the EDRF donor aortic segment did not alter the magnitude of EDR. 4] Among the inorganic $Ca^{2+}$-antagonists $Mn^{2+}$ and $Cd^{2+}$ did not inhibit EDR, whereas $Co^{2+}$ and $La^{3+}$ inhibited EDR. 5] The inhibitory response of $Co^{2+}$ to EDR developed when infused directly on the test strip. That of $La^{3+}$, however, was evoked when added to solution perfusing the donor aortic segment. The above results suggest that $Ca^{2+}$-antagonists do not affect EDR and the inhibitory effect of $Ca^{2+}$ results from influencing the action of EDRF on vascular smooth muscle, whereas that of $La^{3+}$ results from its action on the release of EDRF from endothelial cells.

• The Korean Journal of Physiology and Pharmacology
• /
• 제9권5호
• /
• pp.305-314
• /
• 2005

Diabetes mellitus is associated with vascular complications, including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive substances in various vasculature. In the present study, the authors have observed endothelin-B ($ET_B$) receptor agonist-induced relaxation in precontracted mesenteric arterial segments from streptozotocin (STZ)-induced diabetic rats, which was not shown from control rats or in other arterial segments from diabetic rats. Accordingly, the goal of this study was to investigate in what way STZ-induced diabetes altered reactivity of the mesenteric arterial bed and to examine the causal relaxation, if any, between this $ET_B$ receptor-mediated relaxation and endothelial paracrine function, especially nitric oxide (NO) production. The relaxation induced by $ET_B$ agonists was not observed in mesenteric arteries without endothelium. The relaxation to $ET_B$ agonists was completely abolished by pretreatment with BQ788, but not by BQ610. $N_{\omega}-nitro-L-arginine$ methyl ester and soluble guanylate cyclase inhibitors, methylene blue or LY83583 significantly attenuated the relaxant responses to $ET_B$ agonists, respectively. When the expression of eNOS and iNOS was evaluated on agarose gel stained with ethidium bromide, the expression of eNOS mRNA in diabetic rats was significantly decreased, but the expression of iNOS was increased compared with control rats. Furthermore, the iNOS-like immunostaining was densely detected in the endothelium and slightly in the arterial smooth muscle of diabetic rats, but not in control rats. These observations suggest that $ET_B$ receptor may not play a role in maintaining mesenteric vascular tone in normal situation. However, the alterations in $ET_B$ receptor sensitivity were found in diabetic rats and lead to the $ET_B$ agonist-induced vasorelaxation, which is closely related to NO production. In the state of increased vascular resistance of diabetic mesenteric vascular bed, enhanced NO production by activation of iNOS could lead to compensatory vasorelaxation to modulate adequate perfusion pressure to splanchnic area.

• Biomolecules & Therapeutics
• /
• 제26권2호
• /
• pp.139-145
• /
• 2018

The present study was undertaken to investigate the influence of hypothermia on endothelium-independent vascular smooth muscle contractility and to determine the mechanism underlying the relaxation. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Hypothermia significantly inhibited fluoride-, thromboxane $A_{2-}$, phenylephrine-, and phorbol ester-induced vascular contractions regardless of endothelial nitric oxide synthesis, suggesting that another pathway had a direct effect on vascular smooth muscle. Hypothermia significantly inhibited the fluoride-induced increase in pMYPT1 level and phorbol ester-induced increase in pERK1/2 level, suggesting inhibition of Rho-kinase and MEK activity and subsequent phosphorylation of MYPT1 and ERK1/2. These results suggest that the relaxing effect of moderate hypothermia on agonist-induced vascular contraction regardless of endothelial function involves inhibition of Rho-kinase and MEK activities.

• Journal of Ginseng Research
• /
• 제21권2호
• /
• pp.125-132
• /
• 1997

Our previous study showed that in vivo treatment of spontaneously hypertensive rats (SHR) with protopanaxatriol ginsenosides (PPT) reduces the blood pressure and inhibits the con- tractions induced by endothelium-derived contracting factor (prostaglandin endoperoxide ($PGH_2$) and superoxide anion) in aorta isolated from SHR. The aim of the present study is to examine whether PPT improves endothelial functions in the isolated thoracic aorta of SHR in vitro. Treatments of aortic rings with PPT, purified ginsenoside $Rg_1$ ($Rg_1$) or indomethacin normalized endotheliuln-dependent relaxation to acetylcholine, but not with protopanaxadiol ginsenosides (PPD) and purified ginsenoside Rb1 (Rb1). The effects of PPT were dose-dependent. PGH,- and oxygen free radical-inducted contractions in rat aorta without endothelium were inhibited by PPT or $Rg_1$, but not by PPD or $Rb_1$. Contractions induced by PGF2$\alpha$, U-46619, a stable thromboxane A2 agonist or KCI (60 mM) were not inhibited by PPT, $Rg_1$ or $Rb_1$. These findings demonstrate that PPT but not PPD scavenges the oxygen-derived free radicals and/or antagonize the effects of $PGH_2$ in the vascular smooth muscle and may explain the hypotensive effect of ginseng in the SHR.

• 고려인삼학회:학술대회논문집
• /
• 고려인삼학회 1998년도 Advances in Ginseng Research - Proceedings of the 7th International Symposium on Ginseng -
• /
• pp.182-189
• /
• 1998

Administration of ginsenosides, a mixture of saponin extracted from Panax ginseng, decreased blood pressure in rat. Previous studies have shown that ginsenosides caused endothelium-dependent relaxation, which was associated with the formation of cyclic GMP, suggested that ginsenosides caused release of nitric oxide (NO) from the vascular endothelium. The aim of the present study was to characterize the endothelium-independent relaxation to ginsenosides in the isolated rat aorta. Ginsenosides caused a concentration-dependent relaxation of rat aortic rings without endothelium constricted with 25 mM KCI but affected only minimally those constricted with 60 mM KCI. Ginsenoside Rg3 (Rg3) was a more potent vasorelaxing agonist than total ginsenoside mixture and also the ginsenoside PPT and PPD groups. Relaxation to ginsenosides were markedly reduced by TEA, but not by glibenclamide. Rg3 significantly inhibited Cal'-induced concentration-contraction curves and the "50a2'influx in aortic rings incubated in 25 mM KCI whereas those responses were not affected in 60 mM KCI. Rg3 caused efflux of $"Rb in aortic rings that was inhibited by tetraethy- lammonium (TEA), an inhibitor of Ca"-dependent K'channels, but not by glibenclamide, an inhibitor of AfP-dependent K'channels. These findings indicate that ginsenosides may induce vasorelaxation via activation of Ca2'-dependent K'channels resulting in hyperpolarization of the vas- cular smooth muscle with subsequent inhibition of the opening of voltage-dependent Caf'channels. These effects could contribute to explain the red ginseng-associated vasodilation and the beneficial effect on the cardiovascular system.

• 대한약리학회지
• /
• 제31권3호
• /
• pp.285-290
• /
• 1995

이 실험은 여러 파장$(240{\sim}520\;nm)$의 자외선 또는 가시광선(이후 '광선'이라 표기함)을 흰쥐흉부대동맥에 조사하여 이때의 혈관장력의 변화 및 조직내 cyclic GMP농도의 변화를 관찰하기위하여 시행하였다. 돼지관상동맥 또는 흰쥐 흉부대동맥의 환상표본에 spectrofluorometer의 xenon lamp를 이용하여 여러 파장의 광선을 조사하고 이때의 장력변동을 polygraph상에 기록하였다. Cyclic GMP농도변화는 표본에 광선을 조사한 직후 조직을 얼리고 homogenization 및 원침시킨 후 상청액을 ether로 추출하여 RIA kit로 측정하였다. Phenylephrine으로 수축된 내피존재 흰쥐 흉부 대동맥에서는 광선조사로 수축반응을 보였고 320 nm에서 최대수축반응을 일으켰다. 그 이상의 파장에서는 점차 수축반응이 감소되어 420 nm에서는 최대 이완반응을 일으킨 후 점차 기본장력으로 회복되었다. 그러나 내피제거 표본에서는 전파장에서 이완반응만을 일으켰고 이때 최대 이완반응은 370 nm에서 관찰되었다. 내피존재 표본에서 320, 380 및 420 nm의 광선을 30초간 조사한 결과 380과 420nm에서 현저한 cyclic GMP의 증가가 관찰되었으나 320 nm에서는 유의한 변동이 없었다. 한편, 내피제거 표본에서는370 nm의 광선조사로 cyclic GMP함량이 약 4배 증가하였다. 이상의 성적으로부터 흰쥐 흉부대동맥은 광선조사에 의하여 내피존재 표본에서는 수축-이완의 이상성반응을, 제거표본에서는 이완반응만을 일으키고 양 표본의 이완반응은 nitric oxide-cyclic GMP계의 활성화에 기인하나 수축반응은 cyclic GMP계와 직접 관련성이 없는 것으로 추론하였다.

• The Korean Journal of Physiology and Pharmacology
• /
• 제4권3호
• /
• pp.263-270
• /
• 2000

To evaluate the involvement of nitric oxide production on the endothelium-dependent relaxation in diabetes, we have measured vascular and endothelial function and nitric oxide concentration, and the expression level of endothelial nitric oxide synthase in the streptozotocin-induced diabetic rats. Diabetic rats were induced by the injection of streptozotocin (50 mg/kg i.v.) in the Sprague-Dawley rats. Vasoconstrictor responses to norepinephrine (NE) showed that maximal contraction to norepinephrine $(10^{-5}\;M)$ was significantly enhanced in the aorta of diabetic rats. Endothelium-dependent relaxation induced by acetylcholine was markedly impaired in the aorta of diabetic rats, these responses were little improved by the pretreatment with indomethacin. However, endothelium-independent relaxation induced by nitroprusside was not altered in the diabetic rats. Plasma nitrite and nitrate $(NO_2/_3)$ levels in diabetic rats were significantly lower than in non-diabetic rats. Western blot analysis using a monoclonal antibody against endothelial cell nitric oxide synthase (eNOS) revealed that the protein level was lower in the aorta of diabetic rats than in non-diabetic rats. These data indicate that nitric oxide formation and eNOS expression is reduced in diabetes, and this would, in part, account for the impaired endothelium-dependent relaxation in the aorta of streptozotocin-induced diabetic rats.

• Clinical and Experimental Pediatrics
• /
• 제56권3호
• /
• pp.130-134
• /
• 2013

Purpose: Anthracyclines have been utilized in the treatment of children with acute lymphoblastic leukemia (ALL). Recent studies have shown that anthracyclines may induce toxicity in the vascular endothelium. This study was performed using brachial artery reactivity (BAR) to evaluate vascular endothelial function in ALL patients who were treated with anthracycline chemotherapy. Methods: We included 21 children with ALL who received anthracycline chemotherapy and 20 healthy children. The cumulative dose of anthracyclines in the ALL patients was $142.5{\pm}18.2/m^2$. The last anthracycline dose was administered to the patients 2 to 85 months prior to their examination using BAR. The diameter of the brachial artery was measured in both groups using echocardiography, and BAR was calculated as the percentage change in the arterial diameter after release of the cuff relative to the baseline vessel diameter. Results: In the anthracycline-treated group, BAR was observed to be $3.4%{\pm}3.9%$, which was significantly lower than that observed in the control group ($12.1%{\pm}8.0%$, P<0.05). The time elapsed after the last anthracycline treatment and the age at the time of treatment did not affect the change in BAR (P =0.06 and P =0.13, respectively). Conclusion: These results provided evidence that treatment of ALL patients with anthracycline results in endothelial dysfunction. A larger cohort study and a longer follow-up period will be required to clarify the relationship between endothelial dysfunction resulting from anthracycline treatment for childhood ALL and occurrence of cardiovascular diseases later in life.

• The Korean Journal of Physiology and Pharmacology
• /
• 제3권4호
• /
• pp.375-382
• /
• 1999

Growing evidence indicates that enhanced generation or actions of nitric oxide (NO) are implicated in the pathogenesis of hypertension in spontaneously hypertensive rats and diabetic nephropathy in streptozotocin (STZ)-induced diabetic rats. We investigated whether inducible nitric oxide synthase (iNOS) expression in STZ-induced diabetic rats is responsible for the alterations of vascular reactivity. Diabetic state was confirmed 28 days after injection of STZ (i.p) in rats by measuring blood glucose. In order to evaluate whether short term (4 weeks) diabetic state is related with altered vascular reactivity caused by iNOS expression, isometric tension experiments were performed. In addition, plasma nitrite/nitrate (NOx) levels and expression of iNOS in the lung and aorta of control and STZ-treated rats were compared by using Griess reagent and Western analysis, respectively. Results indicated that STZ-treated rats increased the maximal contractile response of the aorta to phenylephrine (PE), and high $K^+,$ while the sensitivity remained unaltered. Endothelium-dependent relaxation, but not SNP-mediated relaxation, was reduced in STZ-treated rats. Plasma nitrite/nitrates are significantly increased in STZ-treated rats compared to controls. The malondialdehyde (MDA) contents of liver, serum, and aorta of diabetic rats were also significantly increased. Furthermore, nitrotyrosine, a specific foot print of peroxynitrite, was significantly increased in endothelial cells and smooth muscle layers in STZ-induced diabetic aorta. Taken together, the present findings indicate that enhanced release of NO by iNOS along with increased lipid peroxidation in diabetic conditions may be responsible, at least in part, for the augmented contractility, possibly through the modification of endothelial integrity or ecNOS activity of endothelium in STZ-diabetic rat aorta.