果糖诱导高血压大鼠血管内皮素-1、内皮素受体-A和内皮源性一氧化氮合酶表达的变化

目的研究果糖诱导高血压和胰岛素抵抗大鼠血管内皮素-1(ET-1)及内皮素-A受体(ETA-R)和内皮源性一氧化氮合酶(eNOS)的变化,探讨内皮功能变化在果糖诱导高血压和胰岛素抵抗中的作用.方法雄性Sprague-Dawley(SD)大鼠饮用10%果糖水3周,尾套法测量血压,并留取血清及尿标本分别测定血清胰岛素、血脂、血糖及血和尿中血ET-1水平后,处死大鼠.ELISA法测定血清及尿中ET-1水平,RT-PCR法测定大鼠主动脉中ET-1及ETA-R表达,Western杂交检测eNOS的表达情况.结果与正常饮水大鼠相比,高果糖饮水3周后,大鼠血压明显升高[(132.8±1.49 vs 120.5±1.7)mmHg,P<0.01]、血胰岛素水平亦明显高于正常饮水组[(12.2±2.3 vs 9.5±1.2)mIu/L,P<0.05].两组间血清ET-1的水平并没有显著差异,但尿中ET-1的水平,果糖饮水组显著高于正常对照组.果糖饮水组大鼠主动脉ET-1和ETA-R的mRNA水平明显升高,而eNOS蛋白质水平显著低于正常组.结论ET-1和ETA-R高表达及eNOS表达的降低参与了果糖诱导高血压和高胰岛素血症的形成.     

果糖诱导高血压大鼠血管内皮素-1、内皮素受体-A和内皮源性一氧化氮合酶表达的变化

目的研究果糖诱导高血压和胰岛素抵抗大鼠血管内皮素-1(ET-1)及内皮素-A受体(ETA-R)和内皮源性一氧化氮合酶(eNOS)的变化,探讨内皮功能变化在果糖诱导高血压和胰岛素抵抗中的作用。方法雄性Sprague-Dawley(SD)大鼠饮用10%果糖水3周,尾套法测量血压,并留取血清及尿标本分别测定血清胰岛素、血脂、血糖及血和尿中血ET-1水平后,处死大鼠。ELISA法测定血清及尿中ET-1水平,RT-PCR法测定大鼠主动脉中ET-1及ETA-R表达,Western杂交检测eNOS的表达情况。结果与正常饮水大鼠相比,高果糖饮水3周后,大鼠血压明显升高[(132.8±1.49 vs 120.5±1.7)mmHg,P<0.01]、血胰岛素水平亦明显高于正常饮水组[(12.2±2.3 vs 9.5±1.2)mIu/L,P<0.05]。两组间血清ET-1的水平并没有显著差异,但尿中ET-1的水平,果糖饮水组显著高于正常对照组。果糖饮水组大鼠主动脉ET-1和ETA-R的mRNA水平明显升高,而eNOS蛋白质水平显著低于正常组。结论ET-1和ETA-R高表达及eNOS表达的降低参与了果糖诱导高血压和高胰岛素血症的形成。     

内皮素和一氧化氮在心血管病中的作用

心血管疾病与血管内皮的关系已被医务界所认识 ,血管内皮所分泌的内皮素— 1及一氧化氮在心血管疾病的发病中起重要作用。所以 ,保护血管内皮功能可以预防心血管疾病     

Increased Gastric Bicarbonate Secretion in Portal Hypertensive Anesthetized Rats (Role of Prostaglandins and Nitric Oxide)

Gastric bicarbonate secretion might be modifiedin portal hypertension as a consequence of theintramucosal increase in prostaglandins and nitric oxidecontent. Therefore, we studied gastric bicarbonate secretion in control and portal hypertensiverats and investigated the role of prostaglandins andnitric oxide. Basal gastric bicarbonate secretion wasstudied in rats, using a gastric pH back-titration technique, two weeks after partial portal veinligation or a sham operation. The effects of thefollowing drugs were investigated: the prostaglandinsynthase inhibitor indomethacin (5 mg/kg intravenously), prostaglandin (PGE₂) (1 mg/kgintravenously), the nitric oxide synthase inhibitorsN^G-nitro-L-arginine methyl ester (LG NAME, 5mg/kg intravenously) andN^G-monomethyl-L-arginine (L-NMMA, 50 mg/kgintravenously), and the nitric oxide donor nitroprusside (5mmol/liter in the gastric perfusate). Plasma leakage inthe gastric wall was also measured after Evans blue dyeinjection in portal hypertensive and sham-operated rats pretreated by indomethacin (5 mg/kg,intravenously) and L-NAME (5 mg/kg, intravenously).Basal bicarbonate secretion was significantly increasedin portal hypertensive rats as compared to controls. After indomethacin, the bicarbonate secretionwas significantly reduced to a similar level in bothgroups. PGE₂ increased bicarbonate secretionsignificantly more in portal hypertensive rats than insham-operated rats. The NO synthase inhibitor L-NMMAsignificantly increased bicarbonate secretion in portalhypertensive rats only, while the other inhibitor,L-NAME, increased it significantly more in portalhypertensive than in the sham-operated rats. Plasma leakagein portal hypertensive rats, which was increased in thebasal condition as compared to control, was furtherenhanced by indomethacin but not by L-NAME pretreatment. The nitric oxide donor significantly reducedbicarbonate secretion in portal hypertensive rats toreach a similar level as in sham-operated rats. Basalgastric bicarbonate secretion is increased in portal hypertensive rats. This could be due to anenhanced prostaglandin mucosal level. Nitric oxide,which reduces bicarbonate secretion, may contribute tolimiting prostaglandin-induced bicarbonateoverproduction.     

Molecular Analysis of Cocaine-Induced Endothelial Dysfunction: Role of Endothelin-1 and Nitric Oxide

Cocaine remains the most frequently used illicit substance. Although cocaine-induced atherosclerosis is well documented, its mechanism of action on human vascular endothelial cells has not been determined. Nitric oxide (NO) and endothelin-1 (ET-1) are involved in endothelial cell activation and leukocyte recruitment. The present study monitored the effects of cocaine on NO and ET-1 production in human aortic endothelial cells (HAECs) and the effects of sodium nitroprusside (SNP) and BQ-123 on leukocyte adhesion to HAECs. Acute exposure to cocaine (1 and 3 μM) significantly increased ET-1 production (2-fold) and ET-1 receptor type-A (ET_AR) protein expression, within 6–12 h. Cocaine exposure for a longer duration (24–72 h) showed a temporal decrease in both NO production and endothelial NO-synthase (eNOS) expression. The cocaine-mediated suppression of NO was ameliorated by co-treatment of cells with the ET_AR blocker, BQ-123 (5 μM). Furthermore, both short-term (24 h) and long-term (72 h) exposure to cocaine increased endothelial adhesion of monocytes (U937 cells) by 20% and 40%, respectively, which were also suppressed by BQ-123 and SNP co-treatment. These data suggest that a concomitant increase in both ET-1 and ET_AR expression in cocaine exposed HAECs may enhance signaling via the ET_AR which decreases eNOS expression and NO production, and ultimately results in endothelial activation and leukocyte adhesion. Our findings implicate a molecular mechanism of action of cocaine and a therapeutic effect of ET_AR-specific inhibitor in suppressing the cocaine-induced endothelial dysfunction.     

一氧化氮和脂质过氧化物在门脉高压性胃病患者中的变化

背景:胃黏膜糜烂是肝硬化患者发生上消化道出血的重要原因之一。目的:探讨血清和胃黏膜内一氧化氮(NO)和脂质过氧化物(LPO)的变化在门脉高压性胃病(PHG)发病中的作用。方法:将43例PHG患者随机分为两组,20例患者采血清,23例患者取胃黏膜,分别采用硝酸还原法和硫代巴比妥酸(TBA)比色法测定NO和LPO含量。结果:PHG患者血清和胃黏膜内的NO和LPO含量均显著高于对照组(P<0.001)。结论:PHG患者血清和胃黏膜内NO和LPO含量增高可能参与了PHG的发病机制。     

Alterations in the Vasoreactivity of Hypertensive Rat Aortic Rings: Role of Nitric Oxide and Superoxide Radicals

Objectives:Present study was undertaken to investigate involvement of nitric oxide (NO) and superoxide radicals in the modulation of vasoreactivity in a model of renal hypertension

Method:Hypertension was induced in the male Sprague Dawley rats by aortic banding just above the left kidney. Relaxation or contraction following cumulative addition of acetylcholine (Ach, 1 × 10^-8to 1 x^-5M) or phenylephrine (PE, 1 × 10^-8to 1 × 10^-5mol/1) was studied in the aortic rings obtained from sharn operated normotensive, hypertensive and captopril pretreated rats. Ach and PE responses were taken in the presence or absence of NO synthase inhibitor (L-NAME; 1 × 10^-5and 1 × 10^-4mol/1). Spontaneous release of NO from the aortic rings was evaluated by studying the inhibition of adenosine phosphate stundated platelet aggregation, while superoxide radcals were estunated by cytochrome c reduction method

Results:Ach induced vasorelaxation in PE precontracted rings was impaired followmg 8 wk alter aorbc bandmg, while spontaneous release of NO remained unaffected. Captopril pretreatment restored the aortic ring responsiveness to Ach. An increase in the superoxide radicalgeneration and PE induced contraction following L-NAME treatment in the hypertensive rat aortic rings was observed

Conclusion:Attenuation in the Ach induced NO release and augmentation in the superoxide radcal generation seems to play an important role in the modulation of vasoreactivity following renal hypertension in rats     

Chronic Inhibition of Nitric Oxide Ameliorates Splanchnic Hyposensitivity to Glypressin in a Hemorrhage-transfused Rat Model of Portal Hypertension

Background: Vasopressin given during hemorrhage is less effective than when given during a stable state in experimental portal hypertension or patients with cirrhosis (the so-called hyposensitivity phenomenon). This study investigated whether chronic inhibition of nitric oxide (NO) synthesis by N^G-nitro-L-arginine methyl ester (L-NAME), a non-selective NO synthase inhibitor, could potentiate the portal-hypotensive effect of glypressin (a long-acting vasopressin analogue) in portal-hypertensive rats during acute bleeding status. Methods: Portal hypertension was induced by partial portal vein ligation (PVL). Rats were divided to receive either L-NAME (~25 mg/kg/day in tap water) or placebo (tap water) treatment orally from 2 days prior to until 14 days after the operation. At the end of treatment, L-NAME-and placebo-treated PVL rats were subdivided into without-bleeding and with-bleeding groups to assess the effects of glypressin (0.07 mg/kg) on systemic and portal hemodynamics. In rats with a hypotensive hemorrhage, 4.5 ml of blood was withdrawn and 50% of the withdrawn blood was reinfused before the administration of glypressin. Results: As compared with placebo-treated rats, chronic treatment with L-NAME in PVL rats significantly increased mean arterial pressure (P &lt; 0.001) without modulating portal pressure (P &gt; 0.05). In placebo-treated PVL rats, glypressin resulted in a less decrease in portal pressure in rats with bleeding than in those without bleeding (P &lt; 0.05). For PVL rats with bleeding, the portal-hypotensive effect of glypressin was significantly potentiated after chronic L-NAME treatment (P &lt; 0.05). Conclusions: Chronic inhibition of NO alleviates the splanchnic hyposensitivity to glypressin observed in bleeding PVL rats, suggesting the pathophysiological role of nitric oxide in mediating this splanchnic hyposensitivity.     

Big Endothelin-1 and Nitric Oxide in Hypertensive Elderly Patients with and without Obstructive Sleep Apnea-Hypopnea Syndrome

Background

The role of oxidative stress in hypertensive elderly patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) is unknown.

Objective

The purpose was to evaluate the levels of big endothelin-1 (Big ET-1) and nitric oxide (NO) in elderly hypertensive patients with and without moderate to severe OSAHS.

Methods

Volunteers were hospitalized for 24 h. We obtained the following data: body mass index (BMI); 24-ambulatory blood pressure monitoring; and current medication. Arterial blood was collected at 7pm and 7am for determining plasma NO and Big ET-1 levels. Pulse oximetry was performed during sleep. Pearson''s or Spearman''s correlation and univariate analysis of variance were used for statistical analysis.

Results

We studied 25 subjects with OSAHS (group 1) and 12 without OSAHS (group 2) aged 67.0 ± 6.5 years and 67.8 ± 6.8 years, respectively. No significant differences were observed between the groups in BMI; number of hours of sleep; 24-h systolic and diastolic BPs; awake BP, sleep BP and medications to control BP between groups. No differences were detected in plasma Big ET-1 and NO levels at 19:00 h, but plasma Big ET-1 levels at 7:00 h were higher in group 1 (p = 0.03). In group 1, a negative correlation was also observed between the mean arterial oxyhemoglobin saturation level, 24-h systolic BP (p = 0.03, r = −0.44), and Big ET-1 (p = 0.04, r = −0.41).

Conclusions

On comparing elderly hypertensive patients with and without OSAHS having similar BP and BMI, we observed higher Big ET-1 levels After sleep in the OSAHS group. NO levels did not differ between the hypertensive patients with or without OSAHS.     

Nitric Oxide and Portal Hypertension

In liver cirrhosis, an increase in hepatic resistance is the initial phenomenon leading to portal hypertension. This is primarily due to the structural distortion of the intrahepatic microcirculation caused by cirrhosis. However, similar to other vascular conditions, architectural changes in the liver are associated with a deficient nitric oxide (NO) production, which results in an increased vascular tone with a further increase in hepatic resistance and portal pressure. New therapeutic strategies are being developed to selectively provide the liver with NO, overcoming the deleterious effects of systemic vasodilators. On the other hand, a strikingly opposite process occurs in splanchnic arterial circulation, where NO production is increased. This results in splanchnic vasodilatation and subsequent increase in portal inflow, which contributes to portal hypertension. Systemic blockade of NO in portal hypertension attenuates the hyperdynamic circulation, but its effects increasing hepatic resistance may offset the benefit of reducing portal inflow, thus preventing an effective reduction of portal pressure. Moreover, it cannot be ruled out that NO blockade may have a deleterious action on cirrhosis progression, which raises caution about their use in patients with cirrhosis.     

Distribution of Nitric Oxide Synthase and Secretory Role of Exogenous Nitric Oxide in the Isolated Rat Pancreas

Summary Background. Pancreatic production and in vivo effects of nitric oxide (NO) have been shown by several studies. In order to examine the direct actions of the NO donor sodium nitroprusside (SNP), this study used in vitro specimens of the rat pancreas where the distribution of neuronal nitric oxide synthase (NOS) and the secretory effects of SNP and the cyclic GMP (cGMP) analog 8-bromo cyclic GMP (8-Br cGMP) were investigated. Methods. NO containing pancreatic nerves were visualized by NOS immunohistochemistry. Basal and stimulated amylase output from rat pancreatic segments was measured by an on-line fluorimetric method Stimulation was achieved by either acetylcholine (ACh) or electrical field stimulation (EFS). Intracellular free calcium concentration ([Ca²⁺]_i) was measured in dispersed pancreatic acinar cells. Results. NOS containing nerves were demonstrated in the vicinity of pancreatic acini and blood vessels. SNP and 8-Br cGMP inhibited both basal and EFS evoked amylase output but failed to inhibit ACh induced amylase output. Basal [Ca²⁺]_i was decreased by both SNP and 8-Br cGMP but neither SNP nor 8-Br cGMP influenced the ACh evoked increase in [Ca²⁺]_i. Conclusion. NO is well distributed in the rat exocrine pancreas. Exogenous nitric oxide may have a dual action in the isolated rat pancreas: Inhibition of basal amylase secretion in acinar cells and inhibition of ACh release from intrinsic nere terminals. Both effects seem to be calcium dependent and possibly mediated by cGMP.     

气体信号分子硫化氢与一氧化氮在高血压患者中的变化探讨

目的:探讨气体信号分子硫化氢(H2S)及一氧化氮(NO)在高血压中的作用。方法:选择高血压患者262例,男性135例、女性127例,年龄25~70岁(57.81±12.66)岁。其中初发高血压患者67例(初发高血压组),经治高血压患者195例(经治高血压组)。经治高血压患者中,血压控制良好的患者38例、1级高血压水平68例、2级高血压水平64例、3级高血压水平25例。对上述患者中同时怀疑冠心病者进行冠状动脉造影术,病变冠状动脉≥1支并有70%以上狭窄的患者确定血压合并冠心病32例;并根据中国糖尿病诊断标准判断高血压合并糖尿病38例。同时选取正常对照组52例,男性31例、女性21例,年龄(55.52±14.23)岁。检测入选者的血浆H2S及NO浓度。结果:①血浆H2S在经治高血压组中明显低于正常对照组(P<0.05)。②高血压合并冠心病及糖尿病患者的血浆H2S浓度均明显低于单纯高血压患者(P<0.05)。③在经治高血压患者中,随着血压水平的增加,NO及H2S水平均逐渐降低。3级高血压水平患者的H2S及NO浓度均明显低于血压控制良好者(P<0.05),而1级和2级高血压水平患者血浆NO、H2S与血压控制良好者比较均无显著性(P>0.05)。结论:作为气体信号分子,H2S和NO在高血压的发生和发展中均具有重要作用。     

Role of Endothelin-converting Enzyme-1 in the Suppression of Constitutive Nitric Oxide Synthase in Rat Gastric Mucosal Injury by Indomethacin

Background: Disturbances in nitric oxide generation and the release of a vasoactive peptide, endothelin-1 (ET-1), are well recognized early events in pathogenesis of NSAID-induced gastropathy. In this study using phosphoramidon, a potent inhibitor of endothelin-converting enzyme-1 (ECE-1), we investigated the influence of ET-1 on the expression of constitutive (cNOS) and inducible nitric oxide synthase (NOS-2) during gastric mucosal injury caused by indomethacin. Methods: The experiments were conducted with groups of rats pretreated intragastrically with phosphoramidon (10, 20, and 40 mg/kg) or vehicle, followed 30 min later by an intragastric dose of indomethacin (60 mg/kg). The animals were killed 4 h later and their mucosal tissue subjected to macroscopic damage assessment and biochemical measurements. Results: In the absence of phosphoramidon, indomethacin caused extensive multiple hemorrhagic lesions of glandular mucosa, accompanied by a 29.9-fold increase in epithelial cell apoptosis, a 13.3-fold increase in NOS-2 and a 5.5-fold decline in the activity of cNOS, while the mucosal expression of ECE-1 activity increased 4-fold and the level of ET-1 showed a 4.8-fold increase. Pretreatment with phosphoramidon produced dose-dependent reduction in the extent of mucosal damage caused by indomethacin, accompanied by a significant recovery in the expression of cNOS, and a marked decline in ECE-1, epithelial cell apoptosis and the mucosal level of ET-1. Phosphoramidon, however, had no effect on the indomethacin-induced increase in the mucosal expression of NOS-2. Conclusions: The results suggest that suppression of ET-1 generation counters the mucosal drop in cNOS and the extent of gastric mucosal damage caused by indomethacin, but has no effect on the mucosal responses associated with up-regulation of NOS-2 expression. Hence, only cNOS plays a role in the protection of gastric mucosa against damage by NSAIDs.     

Diminished Expression of Constitutive Nitric Oxide Synthases in the Kidney of Spontaneously Hypertensive Rat

In kidney, nitric oxide (NO) synthesized by nitric oxide synthase (NOS) regulates sodium and water excretion, and renal medullary blood flow. The expression of constitutive NOS, endothelial NOS (eNOS) and neuronal NOS (nNOS), were assessed in kidney of the spontaneously hypertensive rat (SHR) and the normotensive Wistar Kyoto (WKY) rat by Western blot analysis and immunocytochemistry. Neuronal NOS expression was observed in the cortex and eNOS was detected only in the inner medulla of both WKY and SHR. In SHR, expression of eNOS was attenuated to 35.1 ± 10.8%, while expression of nNOS was only 57.5 ± 5.7% of the levels seen in WKY rat. Immunocytochemical studies revealed decreased staining of nNOS in the macula densa, collecting ducts and in the glomerulus of SHR compared to WKY rat. Endothelial NOS immunoreactivity was restricted to vascular structures of the inner intima cells and smooth muscle cells, and was markedly reduced in the vasculature of SHR. The decreased renal blood flow observed in SHR may be linked to a diminished expression of eNOS and nNOS, underscoring the importance of these enzymes in the pathophysiology and maintenance of genetic hypertension.     

Modulatory Role of Nitric Oxide/cGMP System in Endothelin-1-Induced Signaling Responses in Vascular Smooth Muscle Cells

Nitric oxide (NO) is an important vasoprotective molecule that serves not only as a vasodilator but also exerts antihypertrophic and antiproliferative effects in vascular smooth muscle cells (VSMC). The precise mechanism by which the antihypertrophic and antiproliferative responses of NO are mediated remains obscure. However, recent studies have suggested that one of the mechanisms by which this may be achieved includes the attenuation of signal transduction pathways responsible for inducing the hypertrophic and proliferative program in VSMC. Endothelin-1 is a powerful vasoconstrictor peptide with mitogenic and growth stimulatory properties and exerts its effects by activating multiple signaling pathways which include ERK 1/2, PKB and Rho-ROCK. Both cGMP-dependent and independent events have been reported to mediate the effect of NO on these pathways leading to its vasoprotective response. This review briefly summarizes some key studies on the modulatory effect of NO on these signaling pathways and discusses the possible role of cGMP system in this process.     

Role of Propolis on Tyrosine Hydroxylase Activity and Blood Pressure in Nitric Oxide Synthase-Inhibited Hypertensive Rats

Reduction in the synthesis or bioavailability of nitric oxide plays a significant role in the development of hypertension. Propolis is a resinous product collected by honeybees from various plant sources. Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the biosynthesis of catecholamines. The aim of this study was to examine the effect of propolis on blood pressure (BP), TH, and total RNA levels in the adrenal medulla, heart, and hypothalamus tissues in chronic nitric oxide synthase (NOS)-inhibited rats by N_w-nitro-l-arginine methyl ester (L-NAME). Rats received NOS inhibitor (L-NAME) for 15 days to produce hypertension and propolis for the last 5 days. TH activity and total RNA levels significantly increased in adrenal medulla, heart, and hypothalamus tissues in L-NAME-treated groups (P < .05). TH activity and total RNA levels of L-NAME+propolis-treated rats reduced (P < .05) compared with L-NAME-treated groups. TH activity in propolis-treated rats was reduced to the control values. L-NAME led to a significant increase in BP compared with the control group. Propolis administration to L-NAME-treated rats reduced BP but this was not statistically significant compared to L-NAME-treated groups. These results suggest that propolis decreases TH activity in NOS-inhibited hypertensive rats and thereby may modulate the synthesis of catecholamine and BP.     

Loss of Pacing-induced Preconditioning in Rat Hearts: Role of Nitric Oxide and Cholesterol-enriched Diet

We examined whether the inhibition of nitric oxide (NO) synthesis by N^G-nitro- -arginine ( NNA) abolished pacing-induced preconditioning, and if prolonged exposure to cholesterol-enriched diet led to the loss of preconditioning due to decreased cardiac NO formation. Therefore, Wistar rats fed 2% cholesterol-enriched diet or standard diet for 24 weeks were treated with a single dose of 1 mg/kg NNA or its solvent at the end of the week 24, respectively. Isolated hearts from all groups were subjected to either preconditioning induced by three consecutive periods of pacing at 600 beats/min for 5 min, with 5-min interpacing periods, or time-matched non-preconditioning perfusion, followed by a 10-min coronary occlusion, respectively. In the control group, coronary occlusion after a non-preconditioning protocol decreased aortic flow (AF) from 45.4±2.4 to 15.6±1.5 ml/min, and resulted in a lactate dehydrogenase (LDH) release of 219±55 mU/min/g, however, preconditioning attenuated the consequences of coronary occlusion [AF: 27.3±1.7 ml/min (P<0.05); LDH: 44±14 mU/min/g (P<0.05)]. Preconditioning did not confer protection in the NNA-treated (AF: 17.4±1.5 ml/min; LDH: 151±21 mU/min/g), and/or in the high-cholesterol-fed groups (AF: 15.7±1.2 ml/min; LDH: 168±22 mU/min/g). Preconditioning was preserved however, when hearts were treated with NNA after the preconditioning protocol [AF: 29.6±2.2 ml/min (P<0.05); LDH: 48±17 mU/min/g (P<0.05)]. Both NNA treatment and cholesterol-enriched diet markedly decreased cardiac NO content assayed by electron spin resonance spectroscopy. We conclude that NO may be involved in the triggering mechanism of pacing-induced preconditioning, the protective effect of which is blocked by sustained exposure to dietary cholesterol, possibly by influencing cardiac metabolism of NO.     

Internal Mammary Artery Grafts Reactivity in Hypertensive Patients: Role of Stretching in Extraendothelial Nitric Oxide

Background. The internal mammary artery (IMA) used in bypass coronary surgery remains efficient for a longer time than other grafts, such as saphenous veins; however, its biological characteristics are incompletely defined. Objective. To compare in IMA grafts from hypertensive (HT) and normotensive (NT) patients the presence of endothelium and their functionability, the response to passive stretching and basal tone, the reactivity to exogenous vasoconstrictors, the role of stretching in NO release, and the possible extraendothelial NO source. Methods and Results. IMA rings contractility, presence of endothelium, and nitrite release were studied. An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching, resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP; however, a lesser response was found in HT. Interestingly, it was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction and that stretching increased NO release. This effect was inhibited by Ca²⁺-free media, _L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, the demonstration of the presence of nNOS in smooth muscle cells by immunohistochemistry supports a role of extraendothelial NO. Conclusion. We demonstrate the impact of hypertension in IMA grafts producing increased endothelial dysfunction, reduced response to passive stretching, increased basal tone, and impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO, even in the absence of the endothelium.     

Role of Nitric Oxide in Cardiovascular Alterations

The overproduction of nitric oxide (NO) during sepsis and septic shock is a key factor in the cardiovascular alterations associated with these conditions. The underlying mechanisms of NO overproduction probably implicate increased activity of the constitutive and inducible isoform of the NO synthase enzyme located in the myocardium and the vascular wall. However, the effects of NO can be desirable, as this endogenous vasodilator helps to maintain blood flow, or detrimental as it can lower peripheral perfusion pressure or induce cellular tissue damage. Therefore, whether manipulating the NO pathway is appropriate in clinical sepsis cannot be presently established, but the answer can be hoped from a better knowledge of the role of NO in each vascular bed, and the use of selective isoform NO synthase inhibitors.     

高血压大鼠ACE2的表达及其与一氧化氮相关性分析

目的探讨血管紧张素转换酶2(ACE2)在自发性高血压大鼠(SHR)中的表达情况并对其与血清一氧化氮(NO)水平作相关性分析。方法分别采用实时荧光定量PCR,Northern印迹以及免疫印迹技术测定心、肾组织中ACE2的mRNA与蛋白表达情况,同时用硝酸还原酶法检测血清NO含量。结果与WKY对照组相比,SHR大鼠心、肾组织中ACE2的mRNA和蛋白表达均明显下降(ACE2/GAPDH mRNA拷贝数比值为:心脏0·043±0·012vs1.291±0·619;肾脏0·051±0·016vs0·914±0·433,P均<0·01;蛋白相对OD值为:心脏0·729±0·046vs1±0·053;肾脏0·734±0·063vs1.005±0·05,P均<0·01),同时出现血清NO浓度下降[(24.3±8.0vs78.4±27.9)μmol/L,P<0·01)。相关分析发现,大鼠血清NO水平与心、肾组织中ACE2/GAPDH的mRNA拷贝数比值呈正相关(r=0·610,0·521,P均<0·05),而与血压水平则呈负相关(r=-0·656,P<0·05)。结论SHR大鼠心、肾组织中ACE2的mRNA和蛋白表达均明显下降,很可能与体内NO水平降低及血压上升有关。特异性影响ACE2转录和表达的药物将对高血压病的防治有重要的临床应用价值。