Intensive lipid lowering by statin therapy does not improve vasoreactivity in patients with type 2 diabetes

Cardiovascular disease is the most important cause of morbidity and mortality in patients with type 2 diabetes. Endothelial dysfunction predicts cardiovascular outcome. Type 2 diabetes is characterized by endothelial dysfunction, which may be caused by dyslipidemia. Statin therapy restores endothelial function in hyperlipidemic patients. Therefore, we hypothesize a beneficial effect of atorvastatin on NO-dependent vasodilation in patients with type 2 diabetes and mild dyslipidemia (low density lipoproteins >4.0 mmol/L and/or triglycerides >1.8 mmol/L). We evaluated the effect of intensive lipid lowering (4 weeks of 80 mg atorvastatin once daily) on vasoreactivity in 23 patients with type 2 diabetes by using venous occlusion plethysmography. Twenty-one control subjects were matched for age, sex, body mass index, blood pressure, and smoking habits. The ratio of blood flows in the infused (measurement [M]) and noninfused (control [C]) arm was calculated for each recording (M/C ratio), and M/C% indicates the percentage change from the baseline M/C ratio. Serotonin-induced NO-dependent vasodilation was significantly blunted (52+/-30 versus 102+/-66 M/C%, P<0.005), and nitroprusside-induced endothelium-independent vasodilation was modestly reduced (275+/-146 versus 391+/-203 M/C%, P<0.05) in patients with type 2 diabetes compared with control subjects. Despite significant reduction of total cholesterol, low density lipoproteins, and triglycerides (5.8+/-1.0 to 3.2+/-0.6 [P<0.0001], 4.1+/-1.1 to 1.8+/-0.7 [P<0.0001], and 2.2+/-1.3 to 1.4+/-0.5 [P<0.05] mmol/L, respectively), no effect on NO-dependent (59+/-44 M/C%) and endothelium-independent (292+/-202 M/C%) vasodilation was demonstrated. These data suggest that intensive lipid lowering by atorvastatin has no effect on NO availability in forearm resistance arteries in type 2 diabetic patients. Other factors, such as hyperglycemia, may be a more important contributing factor regarding impaired vasoreactivity in this patient group.     

三七总皂苷对非酒精性脂肪性肝病小鼠肝组织脂质沉积及NO/iNOS/NF-κB通路的影响

目的 研究三七总皂苷(PNS)对非酒精性脂肪性肝病(NAFLD)小鼠肝脏脂质沉积及一氧化氮(NO)-诱导型一氧化氮合酶(iNOS)-核因子κB(NF-κB)信号通路的影响.方法 随机将40只雄性BALB/c小鼠分为对照组、模型组、三七总皂苷(PNS)干预组和辛伐他汀干预组,每组10只.采用高脂饲料持续喂养法建立NAFL...     

Role of endothelin in the increased vascular tone of patients with essential hypertension

We investigated the possible role of endothelin in the increased vasoconstrictor tone of hypertensive patients using antagonists of endothelin receptors. Forearm blood flow (FBF) responses (strain-gauge plethysmography) to intraarterial infusion of blockers of endothelin-A (ETA) (BQ-123) and endothelin-B (ETB) (BQ-788) receptors, separately and in combination, were measured in hypertensive patients and normotensive control subjects. In healthy subjects, BQ-123 alone or in combination with BQ-788 did not significantly modify FBF (P=0.78 and P=0.63, respectively). In hypertensive patients, in contrast, BQ-123 increased FBF by 33+/-7% (P<0.001 versus baseline), and the combination of BQ-123 and BQ-788 resulted in a greater vasodilator response (63+/-12%; P=0.006 versus BQ-123 alone in the same subjects). BQ-788 produced a divergent vasoactive effect in the two groups, with a decrease of FBF (17+/-5%; P=0.004 versus baseline) in control subjects and transient vasodilation (15+/-7% after 20 minutes) in hypertensive patients (P<0.001, hypertensives versus controls). The vasoconstrictor response to endothelin-1 was slightly higher (P=0.04) in hypertensive patients (46+/-4%) than in control subjects (32+/-4%). Our data indicate that patients with essential hypertension have increased vascular endothelin activity, which may be of pathophysiological relevance to their increased vascular tone. In these patients, nonselective ETA and ETB blockade seems to produce a greater vasodilator effect than selective ETA blockade.     

Acute inhibition of myoglobin impairs contractility and energy state of iNOS-overexpressing hearts

Elevated cardiac levels of nitric oxide (NO) generated by inducible nitric oxide synthase (iNOS) have been implicated in the development of heart failure. The surprisingly benign phenotype of recently generated mice with cardiac-specific iNOS overexpression (TGiNOS) provided the rationale to investigate whether NO scavenging by oxymyoglobin (MbO2) yielding nitrate and metmyoglobin (metMb) is involved in preservation of myocardial function in TGiNOS mice. 1H nuclear magnetic resonance (NMR) spectroscopy was used to monitor changes of cardiac myoglobin (Mb) metabolism in isolated hearts of wild-type (WT) and TGiNOS mice. NO formation by iNOS resulted in a significant decrease of the MbO2 signal and a concomitantly emerging metMb signal in spectra of TGiNOS hearts only (DeltaMbO2: -46.3+/-38.4 micromol/kg, DeltametMb: +41.4+/-17.6 micromol/kg, n=6; P<0.05) leaving contractility and energetics unaffected. Inhibition of the Mb-mediated NO degradation by carbon monoxide (20%) led to a deterioration of myocardial contractility in TGiNOS hearts (left ventricular developed pressure: 78.2+/-8.2% versus 96.7+/-4.6% of baseline, n=6; P<0.005), which was associated with a profound pertubation of cardiac energy state as assessed by 31P NMR spectroscopy (eg, phosphocreatine: 13.3+/-1.3 mmol/L (TGiNOS) versus 15.9+/-0.7 mmol/L (WT), n=6; P<0.005). These alterations could be fully antagonized by the NOS inhibitor S-ethylisothiourea. Our findings demonstrate that myoglobin serves as an important cytoplasmic buffer of iNOS-derived NO, which determines the functional consequences of iNOS overexpression.     

老年高血压病并下肢动脉硬化症的血管内皮功能

目的了解老年高血压病及高血压病合并下肢动脉硬化症(LEASD)患者内皮依赖性舒张功能(FMD)、非内皮依赖性舒张功能(NMD)以及血浆一氧化氮(NO)、内皮素(ET)的水平。方法采用高分辨率超声诊断系统分别检测36例老年高血压病(老年高血压组)患者以及49例老年高血压病合并LEASD(老年高血压合并LEASD组)患者肱动脉的FMD及NMD;同时采用硝酸盐镉还原、比色法测定NO水平(以硝酸盐浓度表示);采用放射免疫法检测ET水平,并分别与40例健康老人(健康老年组)进行对照研究。结果老年高血压合并LEASD组患者肱动脉的FMD及NMD均显著低于老年高血压组和健康老年组(P<0.05),而老年高血压组患者的FMD和NMD亦显著低于健康老年组(P<0.05);老年高血压合并LEASD组患者的NO水平显著低于老年高血压组和健康老年组,而ET却显著高于老年高血压组和健康老年组,而老年高血压组患者NO水平同样显著低于健康老年组,ET水平显著高于健康老年组(P<0.05)。结论老年高血压病及高血压病合并LEASD患者肱动脉FMD及NMD均受损;老年高血压病及高血压病合并LEASD患者均存在血管内皮功能失调,且高血压病合并LEASD患者内皮功能紊乱更严重。     

Ramipril dose-dependently increases nitric oxide availability in the radial artery of essential hypertension patients

DESIGN AND PARTICIPANTS: A double-blind, crossover, randomized study was designed to evaluate the effect of 3-month treatment with a lower versus a higher antihypertensive dosage of ramipril (5 or 10 mg/day) on nitric oxide (NO)-dependent vasodilation in 46 untreated patients with essential hypertension. Radial artery flow-mediated dilation (FMD), before and after the intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA), to block NO synthase, and the response to sublingual glyceril trinitrate (GTN, 25 microg) were measured at baseline and after the two treatment periods as a change in artery diameter (computerized system from ultrasound scans). Plasma angiotensin II and oxidative stress markers were also assessed. RESULTS: FMD was significantly (P < 0.01) lower in hypertensive patients (4.6 +/- 1.8%) than in normotensive subjects (7.1 +/- 2.6%), whereas the response to GTN was similar. L-NMMA significantly (P < 0.001) inhibited FMD in normotensive but not in hypertensive subjects. Mean 24-h ambulatory blood pressure, plasma angiotensin II and oxidative stress marker levels were similarly reduced at the end of the two treatment periods. Both dosages of ramipril significantly (P < 0.001) increased FMD (5 mg: 5.9 +/- 2.1%; 10 mg: 6.3 +/- 2.4%) without modifying the response to GTN. However, compared with baseline (11 +/- 19%), the inhibiting effect of L-NMMA on FMD (NO-dependent FMD) was significantly (P < 0.01) greater with ramipril 10 mg (49 +/- 12%) than 5 mg per day (38 +/- 15%). The improvement in FMD and NO-dependent FMD was not related to changes in plasma levels of angiotensin II or markers of oxidative stress. CONCLUSION: Treatment with ramipril at a higher dosage induced a greater improvement in NO-dependent vasodilation compared with the lower antihypertensive dosage in hypertensive patients.     

Distinct roles of estrogen receptors alpha and beta mediating acute vasodilation of epicardial coronary arteries

This study investigated the contribution of estrogen receptors (ERs) alpha and beta for epicardial coronary artery function, vascular NO bioactivity, and superoxide (O(2)(-)) formation. Porcine coronary rings were suspended in organ chambers and precontracted with prostaglandin F(2alpha) to determine direct effects of the selective ER agonists 4,4',4'-(4-propyl-[(1)H]pyrazole-1,3,5-triyl)tris-phenol (PPT) or 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) or the nonselective ER agonist 17beta-estradiol. Indirect effects on contractility to U46619 and relaxation to bradykinin were assessed and effects on NO, nitrite, and O(2)(-) formation were measured in cultured cells. Within 5 minutes, selective ERalpha activation by PPT, but not 17beta-estradiol or the ERbeta agonist DPN, caused rapid, NO-dependent, and endothelium-dependent relaxation (49+/-5%; P<0.001 versus ethanol). PPT also caused sustained endothelium- and NO-independent vasodilation similar to 17beta-estradiol after 60 minutes (72+/-3%; P<0.001 versus ethanol). DPN induced endothelium-dependent NO-independent relaxation via endothelium-dependent hyperpolarization (40+/-4%; P<0.01 versus ethanol). 17beta-Estradiol and PPT, but not DPN, attenuated the responses to U46619 and bradykinin. All of the ER agonists increased NO and nitrite formation in vascular endothelial but not smooth muscle cells and attenuated vascular smooth muscle cell O(2)(-) formation (P<0.001). ERalpha activation had the most potent effects on both nitrite formation and inhibiting O(2)(-) (P<0.05). These data demonstrate novel and differential mechanisms by which ERalpha and ERbeta activation control coronary artery vasoreactivity in males and females and regulate vascular NO and O(2)(-) formation. The findings indicate that coronary vascular effects of sex hormones differ with regard to affinity to ERalpha and ERbeta, which will contribute to beneficial and adverse effects of hormone replacement therapy.     

Isradipine improves endothelium-dependent vasodilation in normotensive coronary artery disease patients with hypercholesterolemia

OBJECTIVE: The dihydropyridine calcium antagonist isradipine has anti-atherosclerotic effects in animals and improves endothelium-mediated nitric oxide (NO)-dependent vasodilation in vitro. As improved endothelial function may be beneficial we investigated its effects in patients with a high likelihood of endothelial dysfunction. DESIGN: Thirty patients (two female, age 55.4 +/- 10.5 years) with known coronary artery disease and elevated (> 6 mmol/l) total cholesterol (cholesterol: mean 6.7 +/- 0.78 mmol/l) or a cholesterol/high density lipoproteins (HDL) ratio of > 5 not on lipid lowering therapy, participated in the study. Endothelial vasodilator function was assessed before and after double-blind, randomized administration of isradipine 5 mg/day or placebo for 3 months. METHODS: Endothelial function was assessed as forearm blood flow (FBF, venous occlusion plethysmography) responses to graded brachial artery infusions of acetylcholine (Ach), to the NO-synthase blocker NG-monomethyl-L-arginine (L-NMMA) and to the endothelium-independent vasodilator sodium nitroprusside (SNP). Blood pressure was measured either directly from the brachial arterial or by sphygmomanometer during clinic visits. RESULTS: Blood pressure was unchanged in both groups after 3 months (isradipine: 88.8 versus 92.1 mmHg; placebo: 81.0 versus 82.5 mmHg; NS) but cholesterol levels decreased similarly in both groups (isradipine: 6.7 versus 6.1 mmol/l, NS; placebo: 6.6 versus 5.9 mmol/l, P< 0.05). The vasodilator response to SNP and the decrease in FBF in response to blockade of NO synthesis by L-NMMA were unchanged in both groups. However, isradipine, but not placebo, enhanced the NO-dependent vasodilator response to Ach (P < 0.05). CONCLUSION: Isradipine improves acetylcholine-mediated vasodilation in hypercholesterolemic patients independent of changes in lipids or blood pressure.     

肿瘤坏死因子α诱导脑血管内皮细胞产生病理性一氧化氮的实验研究

目的探讨肿瘤坏死因子α（TNF—α）作用于脑血管内皮细胞产生病理性一氧化氮（NO）的机制。方法体外培养肿瘤坏死因子受体（TNFR1）基因敲除的小鼠脑血管内皮细胞（BVEC／RI）和野生型小鼠脑血管内皮细胞（BVEC）,分别给予5ng／ml TNF-α刺激24h后,应用PCR技术、Western blot方法、硝酸还原酶法,测定两种细胞的诱导型一氧化氮合酶（iNOS）基因mRNA和蛋白表达量以及所分泌的一氧化氮（NO）含量。结果①给予TNF—α刺激后,野生型BVEC的iNOS mRNA表达增加,BVEC／RI的iNOS mRNA表达未出现明显变化。②给予TNF—α刺激后,野生型BVEC的iNOS蛋白表达量（0．91±0．08）高于未给予TNF-α的BVEC（0．15±0．02）,差异有统计学意义,P〈0．05;BVEC／RI的iNOS蛋白表达量（0．21±0．06）与未给予TNF—α的BVEC／RI（0．30±0．05）相比,差异无统计学意义,P〉0．05。③给予TNF-α刺激后,野生型BVEC的NO含量[（58．6±2．6）μxmol／L]高于未给予TNF—α的BVEC[（18．1±4．3）μmol／L],差异有统计学意义,P〈0．05;BVEC／RI的NO含量[（21．2±3．5）μmol／L]与未给予TNF-α的BVEC／RI[（16．9±3．4）μmol／L]相比,差异无统计学意义,P〉0．05。结论TNF—α可能通过作用于脑血管内皮细胞TNFR1增加iNOS表达,从而增加病理性NO产生。     

Effect of urate on nitric oxide microcirculatory response in the rat tail to body heating

OBJECTIVE: The objective of this study was to determine if nitric oxide (NO)-mediated cutaneous vasodilation depends on urate concentrations. METHODS: Capillary blood cell velocities (BCV) in the tail capillary vessels of anesthetized, heat-stressed Sprague-Dawley rats were measured by the videomicroscopy method, and the femoral mean arterial pressure (MAP) was recorded on a Grass polygraph. The effects of urate or urate and NO production on the above parameters were determined by using specific inhibitors of these compounds, for example, allopurinol (All) or All or N-nitro-L-arginine (NNA), respectively. Urate concentrations were determined by an enzymatic, colorimetric method, and total nitrite levels were measured fluorometrically. RESULTS: During heat stress, All or All and NNA significantly decreased plasma urate or urate and total nitrite concentrations, respectively, and the response of vascular conductance (estimated as a ratio of BCV to MAP). Urate administration, after All and NNA pretreatment, restored plasma urate and total nitrite concentrations and increased BCV/MAP. CONCLUSIONS: Urate at physiological concentration helps to maintain vascular conductance of cutaneous capillaries in the rat tail during body heating. The effect of urate on vascular conductance may be mediated by NO.     

Impairment of the nitric oxide–mediated vasodilator response to mental stress in hypertensive but not in hypercholesterolemic patients

Objectives. This study investigated whether mental stress–induced vasodilation mediated by endothelium-derived nitric oxide (NO) is defective in conditions with endothelial dysfunction, such as hypertension and hypercholesterolemia.Background. Vascular release of NO modulates the vasodilator response to mental stress in healthy subjects. Previous studies have shown that hypertensive and hypercholesterolemic patients have impaired endothelium-dependent vasodilation to pharmacologic agents due to decreased NO activity. However, whether this abnormality also operates in response to physiologic stimuli such as mental stress has not been defined.Methods. Forearm blood flow responses (plethysmography) to mental stress were compared in 12 normal subjects, 12 hypertensive patients and 10 hypercholesterolemic patients before and during NO synthesis inhibition with N^G-monomethyl-l-arginine (4 μmol/min). Vascular responses to acetylcholine (7.5, 15 and 30 μg/min), an endothelium-dependent vasodilator, and sodium nitroprusside (0.8, 1.6 and 3.2 μg/min), an exogenous NO donor, were also assessed in each group.Results. During saline the vasodilator response to mental stress was significantly blunted in hypertensive (37 ± 11%; p = 0.01) but not in hypercholesterolemic (85 ± 21%; p = 0.78) patients compared with controls (93 ± 15%). N^G-Monomethyl-l-arginine administration significantly blunted mental stress–induced vasodilation in healthy subjects (p = 0.004 vs. saline) and hypercholesterolemic patients (p = 0.03 vs. saline), but not in hypertensive patients (p = 0.69 vs. saline). The vasodilator effect of the highest dose of acetylcholine was similarly blunted in hypertensive (215 ± 44%; p = 0.02) and hypercholesterolemic (172 ± 71%; p = 0.02) patients compared with controls (364 ± 34), whereas the vasorelaxing response to sodium nitroprusside was similar in the three groups.Conclusions. Hypertensive but not hypercholesterolemic patients have impaired NO-dependent vasodilation during mental stress. These findings may be accounted for by different mechanisms underlying endothelial dysfunction in these two conditions and might explain an increased susceptibility of hypertensive patients to vascular damage over repeated exposure to stressful situations.     

Flow-induced dilation of human coronary arterioles: important role of Ca(2+)-activated K(+) channels

BACKGROUND: Flow-induced vasodilation (FID) is a physiological mechanism for regulating coronary flow and is mediated largely by nitric oxide (NO) in animals. Because hyperpolarizing mechanisms may play a greater role than NO in the microcirculation, we hypothesized that hyperpolarization contributes importantly to FID of human coronary arterioles. METHODS AND RESULTS: Arterioles from atria or ventricles were cannulated for videomicroscopy. Membrane potential of vascular smooth muscle cells (VSMCs) was measured simultaneously. After constriction with endothelin-1, increases in flow induced an endothelium-dependent vasodilation. Nomega-Nitro-L-arginine methyl ester 10(-4) mol/L modestly impaired FID of arterioles from patients without coronary artery disease (CAD), whereas no inhibition was seen in arterioles from patients with CAD. Indomethacin 10(-5) mol/L was without effect, but 40 mmol/L KCl attenuated maximal FID. Tetraethylammonium 10(-3) mol/L but not glibenclamide 10(-6) mol/L reduced FID. Charybdotoxin 10(-8) mol/L impaired both FID (15+/-3% versus 75+/-12%, P<0.05) and hyperpolarization (-32+/-2 mV [from -28+/-2 mV after endothelin-1] versus -42+/-2 mV [-27+/-2 mV], P<0.05). Miconazole 10(-6) mol/L or 17-octadecynoic acid 10(-5) mol/L reduced FID. By multivariate analysis, age was an independent predictor for the reduced FID. Conclusions-We conclude that shear stress induces endothelium-dependent vasodilation, hyperpolarizing VSMCs through opening Ca(2+)-activated K(+) channels in human coronary arterioles. In subjects without CAD, NO contributes to FID. NO and prostaglandins play no role in patients with CAD; rather, cytochrome P450 metabolites are involved. This is consistent with a role for endothelium-derived hyperpolarizing factor in FID of the human coronary microcirculation.     

Regulation of cytokine-induced nitric oxide synthesis by asymmetric dimethylarginine: role of dimethylarginine dimethylaminohydrolase

In response to vascular insults, inflammatory cytokines stimulate vascular smooth muscle cells (SMCs) to express an inducible isoform of nitric oxide synthase (iNOS). Asymmetric dimethylarginine (ADMA), an endogenous NO synthase inhibitor, is metabolized by dimethylarginine dimethylaminohydrolase (DDAH). To determine whether the ADMA-DDAH system regulates cytokine-induced NO production, cultured rat SMCs were exposed to interleukin-1beta (IL-1beta). IL-1beta (1 to 100 U/mL) dose-dependently stimulated not only iNOS but also DDAH expression and enzyme activity, accompanied by an increase in NO metabolite and by a decrease in ADMA content in culture media. A DDAH inhibitor (4124W, 5 mmol/L) augmented ADMA production (P<0.01) and decreased NO synthesis (P<0.01) in IL-1beta-stimulated SMCs. On the other hand, an adenovirus-mediated overexpression of DDAH reduced ADMA and enhanced NO production. Exogenous administration of NO donors (SNAP and SIN-1) dose-dependently increased NO metabolite in the culture media but had no effect on ADMA. Our results indicate two mechanisms of IL-1beta-induced NO synthesis: the direct stimulation of the expression of iNOS and the indirect stimulation of iNOS activity by upregulating DDAH and reducing ADMA. The ADMA-DDAH system may be another regulatory mechanism of inflammation-mediated NO production for human vascular diseases.     

Distinct and combined vascular effects of ACE blockade and HMG-CoA reductase inhibition in hypertensive subjects

Hypercholesterolemia and hypertension are frequently associated with elevated sympathetic activity. Both are independent cardiovascular risk factors and both affect endothelium-mediated vasodilation. To identify the effects of cholesterol-lowering and antihypertensive treatments on vascular reactivity and vasodilative capacity, we studied 30 hypercholesterolemic hypertensive subjects. They received placebo for 4 weeks, either enalapril or simvastatin for 14 weeks, and, finally, both medications for an additional 14 weeks. Postischemic forearm blood flow (MFBF) and minimal vascular resistance (mFVR) were used as indices of vasodilative capacity and structural vascular damage, respectively. Total (resting-stress-recovery phases) cardiovascular (blood pressure [BP] and heart rate [HR]) and regional hemodynamic (FBF and FVR) reactivity to stressful stimuli were calculated as area-under-the-curve (auc) (valuextime). Compared with baseline levels, simvastatin reduced total (TOT-C) and LDL cholesterol (LDL-C) (1.27 mmol/L, P<0.001 and 1.33 mmol/L, P<0.001, respectively). Enalapril also reduced TOT-C and LDL-C (0.6 mmol/L, P<0.001 and 0.58 mmol/L, P<0.05, respectively). MFBF was increased substantially by both treatments (P<0.001). Enalapril had a greater effect (-1.7 arbitrary units (AU), P<0.001) than simvastatin (-0.6 AU, P<0.05) on mFVR. During stress, FBF increased more with enalapril (4.4 FBFxminutes, P<0.001) than with simvastatin (1.8 FBFxminutes, P<0.01). Conversely, FVR stress response was reduced more with enalapril (9.1 FVRxminutes, P<0.001) than with simvastatin (2.9 FVRxminutes, P<0.01). During combination treatment, a significant (0.001>P<0.05) additive effect on hypercholesterolemia, structural vascular damage, BP, and FVR was shown. The findings suggest that angiotensin-converting enzyme (ACE) inhibition induces a larger reduction than HMG-CoA reductase blockade in vascular reactivity and structural damage in hypercholesterolemic hypertensive subjects.     

Divergent biological actions of coronary endothelial nitric oxide during progression of cardiac hypertrophy

Coronary endothelial NO synthase expression and NO bioactivity were investigated at sequential stages during the progression of left ventricular hypertrophy. Male guinea pigs underwent abdominal aortic banding or sham operation. Left ventricular contractile function was quantified in isolated ejecting hearts. Coronary endothelial and vasodilator function were assessed in isolated isovolumic hearts in response to boluses of bradykinin (0.001 to 10 micromol/L), substance P (0.01 to 100 micromol/L), diethylamine NONOate (DEA-NO) (0.1 to 1000 micromol/L), N(G)-monomethyl-L-arginine monoacetate (L-NMMA) (10 mmol/L), and adenosine (10 mmol/L). At a stage of compensated left ventricular hypertrophy (3 weeks), left ventricular endothelial NO synthase protein expression was unaltered (Western blot and immunocytochemistry). Vasoconstriction in response to L-NMMA was increased in banded animals compared with sham-operated animals (13.8+/-2.1% versus 6.2+/-1.3%, n=10; P<0.05), but agonist- and DEA-NO-induced vasodilation was similar in the 2 groups. At a stage of decompensated left ventricular hypertrophy (8 to 10 weeks), left ventricular endothelial NO synthase protein expression was significantly lower in banded animals (on Western analysis: banded animals, 7.8+/-0.4 densitometric units; sham-operated animals, 12.2+/-1.7 densitometric units; n=5; P<0.05). At this time point, vasoconstriction in response to L-NMMA was similar in the 2 groups, but vasodilatation in response to bradykinin (30.9+/-2.4% versus 39.7+/-2.2%, n=10; P<0.05), DEA-NO (26.2+/-1.8% versus 34.6+/-1.8%, n=10; P<0.05), and adenosine (24.3+/-2.0% versus 35.7+/-2.0%, n=10; P<0.01) was attenuated in banded animals. These findings indicate that there is an increase in the basal activity of NO (without a significant change in endothelial NO synthase expression) in early compensated left ventricular hypertrophy, followed by a decrease in both endothelial NO synthase expression and NO bioactivity during the transition to myocardial failure.     

Coronary microcirculation in essential hypertension: a quantitative myocardial contrast echocardiographic approach.

AIMS: The aims of the present study were: (a) to demonstrate whether quantitative myocardial contrast echocardiography can detect the increase in coronary flow induced by dipyridamole infusion vasodilation through the myocardial opacification due to the transit of microbubbles, both at rest and after dipyridamole induced vasodilation; (b) to explore the coronary microcirculatory function before and after dipyridamole in two different models: asymptomatic and relatively young hypertensive patients with a mild degree of left ventricular hypertrophy, and healthy controls. METHODS AND RESULTS: Two groups of strictly age-matched males were studied (case-control study): 10, relatively young and asymptomatic essential hypertensive patients with a mild degree of left ventricular hypertrophy with a normal left ventricular function, and 10 healthy controls. The main findings were: the microbubbles' appearance area was significantly lower in hypertensive patients than in controls (P<0.05) because of a significantly lower time to peak. The peak intensity at rest was higher in hypertensives than in controls (P<0.05); but the per cent increase after vasodilatory stimulus was significantly higher in controls (+71% in controls vs +31% in hypertensives; P<0.05). The microbubbles' disappearance area was comparable in both groups at rest; the per cent increase of this parameter after dipyridamole was significantly higher in controls (+124%) than in hypertensives (+90%) (P<0.05). The results achieved in this study documented that the coronary microcirculation in hypertensive patients presenting a mild degree of left ventricular hypertrophy, explored with quantitative myocardial contrast echocardiography, showed a different behaviour in comparison with controls, in the vasodilatory response to dipyridamole. CONCLUSION: The coronary microcirculation in hypertensives showed a reduced vasodilation capacity of the resistance arterioles under dipyridamole induced vasodilatation, and a possible impairment of the endothelium dependent vasodilation. This happened despite an increase in the left ventricular mass, where the relation between capillary bed distribution and hypertrophied myocardium (rarefaction phenomenon) is not completely respected.     

中国高血压最佳治疗情况调查难治性高血压亚组分析

目的探讨中国高血压最佳治疗情况调查(HOT-CHINA)研究中难治性高血压患者的比例和特征。方法对HOT-CHINA研究(2001-04-2002-02)中入选患者(n=54590)治疗情况进行再分析。结果 HOT-CHINA研究人群中难治性高血压占1.9%。与非难治性高血压相比,难治性高血压患者男性多见(65.6%比60.2%),年龄较小[(59.5±13.0)比(61.8±12.3)岁],体质量指数较高[(24.8±3.5)比(24.0±3.4)kg/m2],病程长,空腹血糖、总胆固醇、三酰甘油水平高[分别为(6.60±2.69)比(5.99±2.12)、(5.67±1.63)比(5.32±1.24)、(2.15±1.32)比(1.96±1.09)mmol/L],3级高血压多见(71.1%比27.2%)。代谢综合征、糖尿病、心肌梗死、脑卒中患病率均高于非难治性高血压患者(均P<0.01)。结论难治性高血压多合并有其他危险因素或临床情况,难治性高血压患者要尽早联合用药,控制血压达标。     

Effects of human C-reactive protein on pathogenesis of features of the metabolic syndrome

Major controversy exists as to whether increased C-reactive protein (CRP) contributes to individual components of the metabolic syndrome or is just a secondary response to inflammatory disease processes. We measured blood pressure and metabolic phenotypes in spontaneously hypertensive rats (SHRs) in which we transgenically expressed human CRP in the liver under control of the apolipoprotein E promoter. In transgenic SHRs, serum levels of human CRP approximated the endogenous levels of CRP normally found in the rat. Systolic and diastolic blood pressures measured by telemetry were 10 to 15 mm Hg greater in transgenic SHRs expressing human CRP than in SHR controls (P<0.01). During oral glucose tolerance testing, transgenic SHRs exhibited hyperinsulinemia compared with controls (insulin area under the curve: 36±7 versus 8±2 nmol/L per 2 hours, respectively; P<0.05). Transgenic SHRs also exhibited resistance to insulin stimulated glycogenesis in skeletal muscle (174±18 versus 278±32 nmol of glucose per gram per 2 hours; P<0.05), hypertriglyceridemia (0.84±0.05 versus 0.64±0.03 mmol/L; P<0.05), reduced serum adiponectin (2.4±0.3 versus 4.3±0.6 mmol/L; P<0.05), and microalbuminuria (200±35 versus 26±5 mg of albumin per gram of creatinine, respectively; P<0.001). Transgenic SHRs had evidence of inflammation and oxidative tissue damage with increased serum levels of interleukin 6 (36.4±5.2 versus 18±1.7 pg/mL; P<0.005) and increased hepatic and renal thiobarbituric acid reactive substances (1.2±0.09 versus 0.8±0.07 and 1.5±0.1 versus 1.1±0.05 nmol/L per milligram of protein, respectively; P<0.01), suggesting that oxidative stress may be mediating adverse effects of increased human CRP. These findings are consistent with the hypothesis that increased CRP is more than just a marker of inflammation and can directly promote multiple features of the metabolic syndrome.     

Serum Ionized Magnesium: Relation to Blood Pressure and Racial Factors

To study potential ionic factors predisposing to vascular disease in hypertension, particularly among black subjects, we used a recently developed combined magnesium and calcium specific, ion selective electrode apparatus to measure extracellular ionized calcium (Ca-ion), ionized magnesium (Mg-ion), and Ca-ion/Mg-ion ratios in the serum of fasting, nonmedicated white and black normotensive (n = 61) and hypertensive (n = 23) subjects, studied consecutively in a tertiary referral center.

Both race and blood pressure status had independent effects on the distribution of Mg-ion values. Although Mg-ion levels for the group as a whole were lower in hypertensive versus in normotensive subjects (0.571 ± 0.012 v 0.601 ± 0.005 mmol/L; P < .01), this was only true of white subjects (0.579 ± 0.021 v 0.620 ± 0.006 mmol/L; P = .0095). The lack of a significant difference in Mg-ion levels between black hypertensive versus normotensive subjects (0.553 ± 0.012 v 0.577 ± 0.007 mmol/L, P = NS) was attributable to the significantly lower Mg-ion levels present in normotensive blacks compared to those in normotensive white subjects (0.577 ± 0.007 v 0.620 ± 0.006 mmol/L, P = .0001). Resultant Ca-ion/Mg-ion ratios were elevated in all black subjects and in white hypertensive subjects.

These data support the presence among hypertensives and among black subjects (independently of blood pressure) of a consistent depletion of circulating magnesium and of an imbalance of calcium and magnesium that may potentiate vascular disease among these subjects.     

Effects of hypertension, diabetes mellitus, and hypercholesterolemia on endothelin type B receptor-mediated nitric oxide release from rat kidney

BACKGROUND: Although endothelin-1 is a potent vasoconstrictor peptide, stimulation of endothelin type B receptor (ETBR) causes bidirectional changes in vascular tone, ie, vasodilation and vasoconstriction. Roles of ETBR in pathological conditions are largely unknown. METHODS AND RESULTS: We studied the effect of BQ-3020, a highly selective ETBR agonist, on renal vascular resistance and nitric oxide (NO) release in the isolated, perfused kidney of rats with hypertension, diabetes mellitus, and hypercholesterolemia. Immunohistochemistry of endothelial NO synthase and ETBR was also examined. Infusion of BQ-3020 at concentrations of 相似文献