Effects of atorvastatin and vitamin C on endothelial function of hypercholesterolemic patients

We tested the effects of vitamin C and atorvastatin treatment on endothelium-dependent and endothelium-independent vasodilation in 18 hypercholesterolemic patients (ten men and eight women, aged 20-46 years) in comparison with 12 normal volunteers (seven men and five women, aged 20-45 years). The responses of the forearm blood flow (FBF) to acetylcholine (ACh) (7.5, 15 and 30 microg/min), sodium nitroprusside (SNP) (0.8, 1.6, 3.2 microg/min) and L-NMMA (2, 4, 8 micromol/min) were evaluated at baseline and after 1 month of atorvastatin (10 mg/day) treatment. Drugs were infused into the brachial artery and FBF was measured by strain-gauge plethysmography. At baseline, the response to ACh was significantly attenuated in hypercholesterolemics versus controls: at the highest dose (30 microg/min), FBF was 27.0+/-3.4 versus 11.5+/-1.9 ml.100 ml tissue(-1).min(-1) respectively (P<0.0001). No significant differences were found between groups during SNP infusion. The atorvastatin treatment significantly improved ACh-stimulated FBF: at highest dose the FBF increased to 14.9+/-1.5 ml.100 ml tissue(-1). min(-1) (P<0.0001). Similarly, the L-NMMA endothelial effects were significantly enhanced by lipid-lowering treatment, supporting the improvement of basal nitric oxide. Vitamin C increased ACh-vasodilation in the same way before and after atorvastatin treatment. In conclusion, the endothelial dysfunction in hypercholesterolemics is due to an oxidative stress and atorvastatin rapidly improves both basal and stimulated endothelium-dependent vasodilation.     

Effect of calcium antagonist or beta blockade treatment on nitric oxide-dependent vasodilation and oxidative stress in essential hypertensive patients

OBJECTIVES: Essential hypertension is associated with impaired endothelium-dependent vasodilation caused by oxygen free radical-induced nitric oxide (NO) breakdown. Since calcium antagonists can improve endothelial function in hypertensive patients, we tested whether this beneficial effect could be related to restoration of NO availability by antioxidant activity. METHODS: In 10 healthy subjects and 20 essential hypertensive patients, we studied forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (from 0.15-15 microg/100 ml per min), bradykinin (0.005-0.05 microg/100 ml per min), two endothelium-dependent vasodilators, and sodium nitroprusside (1-4 microg/100 ml forearm tissue per min), an endothelium independent vasodilator, in the absence and presence of NG-monomethyl-L-arginine (L-NMMA) (100 microg/100 ml forearm tissue per min), an NO synthase inhibitor. RESULTS: In controls, vasodilation to acetylcholine and bradykinin was inhibited by L-NMMA. In hypertensive patients, vasodilation to acetylcholine and bradykinin, but not to sodium nitroprusside, was blunted and resistant to L-NMMA. Hypertensive patients were randomized to a 12-week treatment with lacidipine (4-6 mg/daily) or atenolol (50-100 mg/daily) (n = 10 each group). Lacidipine but not atenolol increased the vasodilation to acetylcholine and bradykinin and restored the inhibiting effect of L-NMMA on endothelium-dependent vasodilation, without affecting the response to sodium nitroprusside. Moreover, lacidipine reduced circulating markers of oxidative stress including plasma and low-density lipoprotein (LDL) hydroperoxides, the susceptibility of LDL to Cu2+-induced oxidation and the reactive oxygen species generated from human umbilical vein endothelial cells after incubation with LDL derived from plasma of the patients. CONCLUSIONS: Lacidipine increases endothelium-dependent vasodilation by restoring NO availability, and this effect possibly is related to antioxidant activity.     

Metabolic vasodilation in the human forearm is preserved in hypercholesterolemia despite impairment of endothelium-dependent and independent vasodilation

OBJECTIVE: Hypercholesterolemia has been shown to impair endothelium-mediated, nitric oxide (NO)-dependent responses to acetylcholine (ACh), serotonin, substance P and flow-mediated dilation. We have recently shown that NO contributes to metabolic vasodilation in the human forearm. We sought to determine whether metabolic vasodilation is impaired in healthy subjects with hypercholesterolemia. METHODS: We compared the forearm blood flow (FBF) responses to isotonic exercise, ACh and the endothelium-independent vasodilator sodium nitroprusside in young, otherwise healthy volunteers with hypercholesterolemia and controls before and after the NO inhibitor NG-monomethyl-L-arginine (L-NMMA). FBF was measured using venous occlusion plethysmography. Hypercholesterolemic (n = 20) and control (n = 20) subjects were age- and gender-matched. RESULTS: Total cholesterol (6.9 +/- 0.3 vs. 4.6 +/- 0.1 mmol/l, P < 0.0001), low density lipoprotein (4.9 +/- 0.4 vs. 2.7 +/- 0.1 mmol/l, P < 0.001) and triglyceride (1.3 +/- 0.2 vs. 0.8 +/- 0.1 mmol/l, P = 0.005) levels were higher in the hypercholesterolemic group. Basal FBF and resistance were similar in the two groups. Hypercholesterolemia impaired the peak FBF response to ACh (11.1 +/- 1.9 vs. 17.6 +/- 2.2 ml/100 ml/min, P = 0.03), and reduced the peak response to sodium nitroprusside (6.0 +/- 0.4 vs. 8.1 +/- 0.6 ml/100 ml/min, P < 0.01). However, hypercholesterolemia did not affect peak hyperemic FBF (13.1 +/- 1.0 vs. 13.2 +/- 1.0 ml/100 ml/min, P = 1.0) or the FBF volume repayment during the 1 or 5 min after exercise. Resting FBF was reduced by L-NMMA to a similar degree (by 33% vs. 40%, P = 0.17) in both groups. Although L-NMMA reduced peak hyperemic FBF (by 16% vs. 17%, P = 0.93) and the volume repaid after exercise in both groups, there were no differences between the two groups. CONCLUSIONS: Exercise-induced metabolic vasodilation is in part dependent on NO release. Hypercholesterolemia impairs NO-mediated vasodilation, but is not associated with a reduction in exercise-induced hyperemia. This may indicate that multiple compensatory mechanisms are operative in skeletal muscle metabolic vasodilation.     

Mechanisms responsible for endothelial dysfunction associated with acute estrogen deprivation in normotensive women

BACKGROUND: The goal of this study was to evaluate whether endothelial dysfunction associated with acute estrogen deprivation is caused by an alteration in the L-arginine-nitric oxide (NO) pathway and oxidative stress. Methods and Results-In 26 healthy women (age, 45.7+/-5.4 years) and 18 fertile women with leiomyoma (age, 44.5+/-5.1 years), we studied forearm blood flow (strain-gauge plethysmography) changes induced by intrabrachial acetylcholine (0. 15, 0.45, 1.5, 4.5, or 15 microgram. 100 mL(-1). min(-1)) or sodium nitroprusside (1, 2, or 4 microgram. 100 mL(-1). min(-1)), an endothelium-dependent or -independent vasodilator, respectively. The NO pathway was evaluated by repeating acetylcholine during L-arginine (200 microgram. 100 mL(-1). min(-1); 13 control subjects and 9 patients) or N(G)-monomethyl-L-arginine (L-NMMA; 100 microgram. 100 mL(-1). min(-1); 13 control subjects and 9 patients); production of cyclooxygenase-derived vasoconstrictors was assessed by repeating acetylcholine during indomethacin (50 microgram. 100 mL(-1). min(-1); 13 control subjects and 9 patients) or vitamin C (8 mg. 100 mL(-1). min(-1); 13 control subjects and 9 patients). Patients repeated the study within 1 month after ovariectomy and again after 3 months of estrogen replacement therapy (ERT; 17 beta-estradiol TTS, 50 microgram/d). Basally, vasodilation to acetylcholine was potentiated and inhibited by L-arginine and L-NMMA, respectively (P<0.05), but was unaffected by indomethacin or vitamin C. After ovariectomy, the modulating effect of L-arginine and L-NMMA disappeared, whereas indomethacin and vitamin C potentiated the response to acetylcholine (P<0.05). ERT restored L-arginine and L-NMMA effects on vasodilation to acetylcholine but prevented the potentiation caused by indomethacin or vitamin C. Response to sodium nitroprusside was unaffected by either ovariectomy or ERT. CONCLUSIONS: Endothelial dysfunction secondary to acute endogenous estrogen deprivation is caused by reduced NO availability. Cyclooxygenase-dependent production of oxidative stress could be responsible for this alteration.     

Basal production of nitric oxide (NO) and non-NO vasodilators in the forearm microcirculation in Type 2 diabetes: associations with blood pressure and HDL cholesterol

We examined basal forearm microcirculatory blood flow (FBF) using venous occlusive strain-gauge plethysmography in 47 middle-aged men and women [55+/-1 years] with Type 2 diabetes and 15 age-matched healthy individuals [52+/-3 years], all receiving aspirin. Blood flow was also measured following infusion of N(G)-monomethyl-L-arginine into the brachial artery to inhibit basal NO release (FBF+L-NMMA). Acetylcholine (ACh) and sodium nitroprusside (SNP) were administered to assess endothelium-dependent and endothelium-independent functions. Compared with controls, diabetic subjects had significantly lower vasodilatory responses to ACh and SNP (p<0.05 for each). Basal FBF and FBF+L-NMMA were increased in diabetic subjects compared with controls (2.4+/-0.2 ml/100ml/min versus 1.7+/-0.2 ml/100ml/min, p=0.02 and 1.9+/-0.1 ml/100ml/min versus 1.2+0.1 ml/100ml/min, p=0.01, respectively) whereas the change in FBF following L-NMMA was greater in the controls (-27% versus -19%, p=0.05). Amongst the diabetic subjects, pulse pressure and HDL cholesterol were independent predictors of FBF (b=0.04+/-0.01, adjusted r2=0.21 and p=0.001, and b=3.3+/-1.2, adjusted r2=0.12 and p=0.007, respectively) and FBF+L-NMMA (b=0.03+/-0.01, adjusted r2=0.20, p=0.002 and b=2.1+/-0.9, adjusted r2=0.09 and p=0.02, respectively). Diastolic blood pressure predicted the change in FBF with L-NMMA (b=-1.02+/-0.32, adjusted r2=0.20 and p=0.003). Our findings suggest that well controlled T2DM patients have impaired agonist-mediated vasodilatation of the forearm resistance arteries that is associated with impaired basal release of nitric oxide but an increase in the release of non-NO vasodilators. The latter may be a compensatory response to increased arterial stiffness and may be facilitated by an effect of HDL.     

Rapid improvement of nitric oxide bioavailability after lipid-lowering therapy with cerivastatin within two weeks

OBJECTIVES: We investigated whether improvement of endothelial dysfunction in hypercholesterolemia can be achieved with short-term lipid-lowering therapy. BACKGROUND: Impaired endothelium-dependent vasodilation plays a pivotal role in the pathogenesis of atherosclerosis and acute coronary syndromes. METHODS: In a randomized, double-blind, placebo-controlled trial, we studied 37 patients (52 +/- 11 yrs) with low density lipoprotein cholesterol > or = 160 mg/dl (196 +/- 44 mg/dl) randomly assigned to either cerivastatin (0.4 mg/d) or placebo. Endothelium-dependent vasodilation of the forearm vasculature was measured by plethysmography and intra-arterial infusion of acetylcholine (ACh 12, 48 microg/min) and endothelium-independent vasodilation by intra-arterial infusion of nitroprusside (3.2, 12.8 microg/min). RESULTS: Low density lipoprotein cholesterol decreased after two weeks of treatment (cerivastatin -33 +/- 4% vs. placebo + 2 +/- 4%, x +/- SEM, p < 0.001). Endothelium-dependent vasodilation improved after two weeks of therapy with cerivastatin compared with baseline (ACh 12 microg/min: + 22.3 +/- 5.2 vs. + 11.2 +/- 1.9 ml/min/100 ml, p < 0.01; ACh 48 microg/min: +31.2 +/- 6.3 vs. +19.1 +/- 3.1 ml/min/100 ml, p < 0.05). In contrast, changes in forearm blood flow to ACh were similar before and after therapy in the placebo group (ACh 12 microg/min: + 12.9 +/- 3.6 vs. + 9.0 +/- 1.9 ml/min/100 ml, NS; ACh 48 microg/min: +20.7 +/- 3.7 vs. 19.4 +/- 2.9 ml/min/100 ml, NS). Endothelium-dependent vasodilation improved in comparison with placebo (ACh 48 microg/min: +203 +/- 85% [cerivastatin] vs. -26 +/- 71% [placebo], p < 0.05). This improvement in endothelium-dependent vasodilation was no longer observed when the nitric oxide-synthase inhibitor N(G)-monomethyl-L-arginine was coinfused (ACh 48 microg/min + N(G)-monomethyl-L-arginine 4 micromol/min -48 +/- 85% [cerivastatin]). CONCLUSIONS: Short-term lipid-lowering therapy with cerivastatin can improve endothelial function and NO bioavailability after two weeks in patients with hypercholesterolemia.     

Gly460Trp alpha-adducin gene polymorphism and endothelial function in untreated hypertensive patients

OBJECTIVES: Endothelium-dependent vasodilatation is impaired in essential hypertension. Besides traditional and emerging cardiovascular risk factors, genetic factors may also promote deleterious alterations of endothelial physiology. The aim of the present study was to investigate the relationship between the 460Trp allele of ADD1 and endothelium-dependent vasodilation in 110 never-treated hypertensive patients. METHODS: Forearm blood flow (FBF) was measured during intra-arterial infusion of acetylcholine (ACh) and sodium nitroprusside (SNP) at increasing doses. Analysis of endothelium-dependent and endothelium-independent vasodilation was tested according to ADD1 genotype. RESULTS: The FBF values at the three incremental doses of ACh were 5.22 +/- 0.24 (+76%), 8.64 +/- 0.45 (+193%) and 14.74 +/- 0.71 (+395%) ml/100 ml of tissue per min for Gly460Gly and 4.63 +/- 0.20 (+51%), 6.84 +/- 0.36 (+123%) and 11.22 +/- 3.8 (+269%) ml/100 ml of tissue per min for 460Trp. Thus, ACh-stimulated FBF was significantly reduced in hypertensive subjects carrying the 460Trp allele of ADD1 (P < 0.001). SNP-stimulated FBF was not affected by ADD1. CONCLUSIONS: The main finding in this study was that in essential hypertensives the 460Trp allele of ADD1 is strongly associated with an impaired endothelium-dependent vasodilation, a powerful predictor of cardiovascular risk.     

Effect of oral contraceptives on endothelial function in the peripheral microcirculation of healthy women

OBJECTIVES: We assessed whether third-generation oral contraceptive (OC) treatment (30 microg ethinylestradiol + 75 microg gestodene daily) could affect the endothelial function of healthy women. METHODS: In 20 young healthy women (HW) and 10 hypercholesterolemic women (CW) we assessed forearm blood flow (strain-gauge plethysmography) changes induced by the intrabrachial infusion of acetylcholine (ACH) (0.15-15 microg/100 ml forearm tissue/min) and sodium nitroprusside (SNP) (1-4 microg/100 ml forearm tissue/min). ACH was repeated during the nitric oxide synthase inhibitor intra-arterial NG-monomethyl-L-arginine (L-NMMA) (100 microg/100 ml forearm tissue/min) or the antioxidant vitamin C (8 mg/100 ml forearm tissue/min). HW repeated the protocol after 6-month OC (n = 10) or placebo (n = 10) treatment. RESULTS: In HW the maximal vasodilation to ACH, similar between placebo and OC subgroups, was significantly reduced in CW (P < 0.01). Vasodilation to ACH was blunted (P < 0.01) by L-NMMA and unaffected by vitamin C, in both OC and placebo groups. In CW the vasodilation to ACH, not modified by L-NMMA, was improved by vitamin C (P < 0.01). OC treatment raised (P < 0.01) plasma total and low-density lipoprotein cholesterol, and values were similar to those shown by CW. Both OC and placebo intake did not change the response to ACH and the modulation induced by L-NMMA or vitamin C. Vasodilation to SNP was similar in all groups. CONCLUSIONS: In HW 6-month treatment with third-generation OC, although associated with an abnormal lipid profile, does not adversely affect endothelium-dependent vasodilation. This neutral effect could be the balance between a deleterious effect of hypercholesterolemia and a protective effect of OC on endothelial function.     

Restoration of nitric oxide availability after calcium antagonist treatment in essential hypertension

Essential hypertension is associated with impaired endothelium-dependent vasodilation caused by oxygen free radical-induced nitric oxide (NO) breakdown. Because calcium antagonists can improve endothelial function in patients with essential hypertension, in this study we tested the hypothesis that this beneficial effect could be related to restoration of NO availability by antioxidant properties. In 15 healthy subjects and 15 hypertensive patients, we studied forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (ACh; 0.15, 0.45, 1.5, 4.5, and 15 microg/100 mL per minute), an endothelium-dependent vasodilator in basal conditions, during infusion of N:(G)-monomethyl-L-arginine (L-NMMA, 100 microg/100 mL forearm tissue per minute), an NO-synthase inhibitor, vitamin C (8 mg/100 mL forearm tissue per minute), and finally, simultaneous infusion of L-NMMA and vitamin C. The response to sodium nitroprusside (SNP; 1, 2, and 4 microg/100 mL forearm tissue per minute) was also evaluated. In control subjects, vasodilation to ACh was inhibited by L-NMMA and not changed by vitamin C. In hypertensive patients, vasodilation to ACh was blunted as compared with control subjects and resistant to L-NMMA. Vitamin C, which decreased plasma isoprostanes and increased plasma antioxidant capacity, increased the response to ACh and restored the inhibiting effect of L-NMMA. In hypertensive patients, the study was repeated after 3-month treatment with nifedipine gastrointestinal therapeutic system (30 to 60 mg/daily). Nifedipine treatment decreased circulating plasma lipoperoxides and isoprostanes and increased plasma antioxidant capacity. Moreover, nifedipine increased the vasodilation to ACh but not to SNP and restored the inhibiting effect of L-NMMA on ACh-induced vasodilation, whereas vitamin C no longer exerted its facilitating activity. These results indicate that nifedipine increases endothelium-dependent vasodilation by restoring NO availability, an effect probably determined by antioxidant activity.     

Sickle cell anemia is associated with reduced nitric oxide bioactivity in peripheral conduit and resistance vessels

The purpose of the study was to examine endothelium-dependent and -independent vasodilation of conduit and resistance vessels in sickle cell anemia (HbSS). We measured the effects of intra-arterial infusion of methacholine, sodium nitroprusside, and NG-monomethyl-L-arginine (L-NMMA) on forearm blood flow using venous occlusion plethysmography in eight patients with HbSS and 11 HbAA controls. We assessed vasodilation of the conduit brachial artery using ultrasound in 17 patients with HbSS and 41 nonanemic controls. Forearm blood flow response to methacholine was similar in HbSS and HbAA, while the response to sodium nitroprusside was greater in those with HbSS. Nitric oxide synthase inhibition with L-NMMA attenuated methacholine-induced forearm blood flow to a lesser extent in HbSS compared to HbAA, suggesting diminished nitric oxide (NO) contribution to endothelium-dependent vasodilation. Flow-mediated and nitroglycerin-induced dilation were impaired in HbSS compared to controls and were not affected by the antioxidant vitamin C or the precursor substrate for NO synthesis L-arginine. NO bioactivity is reduced but differs in peripheral conduit and resistance vessels in HbSS. Resistance vessels have preserved response to exogenous NO donors but have diminished contribution of NO to endothelium-dependent vasodilation. Conduit vessels demonstrate impaired vasodilation to endogenous and exogenous NO.     

Effects of acute administration of caffeine on vascular function

Caffeine is the most widely used pharmacologic substance in the world. It is found in common nonessential grocery items (e.g., coffee, tea, cocoa, and chocolate). The effects of caffeine on cardiovascular diseases, including hypertension, remain controversial, and there is little information on its direct effect on vascular function. The purpose of this study was to determine the effect of caffeine on endothelial function in humans. This study was a double-blind, randomized placebo and active drug study. Forearm blood flow (FBF) responses to acetylcholine (ACh), an endothelium-dependent vasodilator, and to sodium nitroprusside, an endothelium-independent vasodilator, were evaluated in healthy young men before and after the oral administration of caffeine 300 mg (n = 10) or placebo (n = 10). FBF was measured by using a strain-gauge plethysmograph. Caffeine significantly increased systolic and diastolic blood pressures by 6.0 +/- 6.0 and 2.6 +/- 3.1 mm Hg (p <0.05), respectively, but did not alter heart rate or baseline FBF. Caffeine augmented the FBF responses to ACh from 21.2 +/- 7.1 to 26.6 +/- 8.1 ml/min/100 ml tissue (p <0.05), whereas sodium nitroprusside-stimulated vasodilation was not altered by caffeine administration. The intra-arterial infusion of N(G)-monomethyl-L-arginine, a nitric oxide synthase inhibitor, abolished the caffeine-induced augmentation of FBF response to ACh. In the placebo group, the ACh- and sodium nitroprusside-stimulated vasodilation was similar before and after the follow-up period. In conclusion, these findings suggest that the acute administration of caffeine augments endothelium-dependent vasodilation in healthy young men through an increase in nitric oxide production.     

The effect of hormonal replacement therapy on the vascular reactivity and endothelial function of healthy individuals and individuals with type 2 diabetes

Estrogens protect healthy women from cardiovascular disease. However, epidemiological data suggest that women with diabetes are denied the cardioprotection associated with estrogens. Whether or not hormonal replacement therapy (HRT) confers cardiovascular benefits in postmenopausal women with diabetes is not known. The aim of this study was to examine the effects of HRT on the microvascular reactivity and endothelial function of individuals with and without diabetes. We studied the following groups of individuals: premenopausal healthy women [n = 28, age 41 +/- 8 yr (mean +/- SD)], premenopausal women with type 2 diabetes (n = 16, age 43 +/- 6 yr); postmenopausal healthy women (n = 12, age 57 +/- 4 yr), postmenopausal women with diabetes (n = 17, age 62 +/- 5 yr); postmenopausal healthy women on HRT (n = 13, age 51 +/- 5 yr), postmenopausal women with diabetes on HRT (n = 11, age 57 +/- 7 yr). We used laser Doppler flowmetry to measure forearm cutaneous vasodilatation in response to iontophoresis of 1% acetylcholine (endothelium dependent) and 1% sodium nitroprusside (endothelium independent). The endothelium-dependent vasodilation was significantly higher in premenopausal healthy women (180 +/- 67%; increase over baseline) compared to premenopausal diabetic women (87 +/- 41%; P < 0.001). endothelium-dependent vasodilation was also higher in postmenopausal healthy women on HRT (143 +/- 52) compared with postmenopausal diabetic women on HRT (86 +/- 61), postmenopausal healthy women without HRT (104 +/- 43), and postmenopausal diabetic women without HRT (74 +/- 28; P < 0.001). A similar pattern of responses was observed in the endothelium-independent vasodilation (premenopausal healthy women, 126 +/- 56; premenopausal diabetic women, 88 +/- 26; postmenopausal healthy women on HRT, 121 +/- 37; postmenopausal diabetic women on HRT, 88 +/- 41; postmenopausal healthy women without HRT, 84 +/- 36; and postmenopausal diabetic women without HRT, 73 +/- 36; P < 0.001). Soluble intercellular adhesion molecule (sICAM) was also measured among all the women with diabetes. Premenopausal women with diabetes (248.9 +/- 56 ng/ml) and postmenopausal women with diabetes on HRT (257.7 +/- 49 ng/ml) had lower sICAM levels compared with the postmenopausal diabetic women without HRT (346.4 +/- 149 ng/ml; P < 0.05). We conclude that menopausal status and type 2 diabetes are associated with impaired microvascular reactivity. HRT substantially improves microvascular reactivity in postmenopausal healthy women. In contrast, the effect of HRT on the microvascular reactivity of postmenopausal diabetic women is less apparent. However, the use of HRT among women with diabetes is associated with lower sICAM levels, suggesting an attenuation in endothelial activation.     

Impaired endothelium-dependent vasodilatation in subclinical hypothyroidism: beneficial effect of levothyroxine therapy

Subclinical hypothyroidism (sHT) is associated with enhanced cardiovascular risk. To test the hypothesis that patients with sHT are characterized by endothelial dysfunction and impaired nitric oxide (NO) availability, in 14 patients [serum cholesterol, 218 +/- 41 mg/dl (5.6 +/- 0.9 mM)] and 28 euthyroid subjects, subdivided into groups A and B [serum cholesterol, 170 +/- 19 mg/dl (4.4 +/- 0.5 mM) and 217 +/- 21 mg/dl (5.6 +/- 0.5 mM), respectively], we studied the forearm blood flow (strain-gauge plethysmography) response to intrabrachial acetylcholine, an endothelium-dependent vasodilator, at baseline and during infusion of N(G)-monomethyl-L-arginine (L-NMMA), a NO synthase inhibitor. Response to sodium nitroprusside and minimal forearm vascular resistances were also evaluated. In sHT patients, vasodilation to acetylcholine was reduced, compared with group B (+358 +/- 29% vs. +503 +/- 19%, P = 0.0003) and group A (663 +/- 65%, P = 0.02 vs. group B and P = 0.0002 vs. sHT). L-NMMA blunted the vasodilation to acetylcholine in groups A and B (49.1 +/- 6.3% and 42.7 +/- 5.5% maximal forearm blood flow reduction, respectively, P < 0.0001 vs. acetylcholine), whereas it was ineffective in sHT patients (12.8 +/- 2.5%). Response to sodium nitroprusside and minimal vascular resistances were similar. In sHT (n = 9) patients, 6 months of euthyroidism by levothyroxine replacement increased acetylcholine-vasodilation and restored L-NMMA inhibition. Patients with sHT are characterized by endothelial dysfunction resulting from a reduction in NO availability, an alteration partially independent of dyslipidemia and reversed by levothyroxine supplementation.     

Intense physical training decreases circulating antioxidants and endothelium-dependent vasodilatation in vivo.

Physical training increases free radical production and consumes antioxidants. It has previously been shown that acute exercise markedly increases the susceptibility of LDL to oxidation but whether such changes are observed during physical training is unknown. We measured circulating antioxidants, lipids and lipoproteins, and blood flow responses to intrabrachial infusions of endothelium-dependent (acetylcholine, ACh, L-N-monomethyl-arginine, L-NMMA) and -independent (sodium nitroprusside, SNP) vasoactive agents, before and after 3 months of running in 9 fit male subjects. Maximal aerobic power increased from 53 +/- 1 to 58 +/- 2 ml/kg min (P < 0.02). All circulating antioxidants (uric acid, SH-groups, alpha-tocopherol, beta-carotene, retinol) except ascorbate decreased significantly during training. Endothelium-dependent vasodilatation in forearm vessels decreased by 32-35% (P < 0.05), as determined from blood flow responses to both a low (10.8 +/- 2.1 vs. 7.3 +/- 1.5 ml/dl min, 0 vs. 3 months) and a high (14.8 +/- 2.6 vs. 9.6 +/- 1.8) ACh dose. The % endothelium-dependent blood flow (% decrease in basal flow by L-NMMA), decreased through training from 37 +/- 3 to 22 +/- 7% (P < 0.05). Blood flow responses to SNP remained unchanged. The decrease in uric acid was significantly correlated with the change in the % decrease in blood flow by L-NMMA (r = 0.74, P < 0.05). The lag time for the susceptibility of plasma LDL to oxidation in vitro, LDL size and the concentration of LDL cholestetol remained unchanged. We conclude that relatively intense aerobic training decreases circulating antioxidant concentrations and impairs endothelial function in forearm vessels.     

Effect of AT1 receptor blockade on endothelial function in essential hypertension

BACKGROUND: Angiotensin II adversely affects endothelial function and NO availability. We analyzed the effect of AT(1) receptor blockade on endothelium-dependent vasodilation and basal nitric oxide (NO) production and release in hypertensive patients. METHODS AND RESULTS: Sixty patients (53 +/- 10 years) with essential hypertension were randomized to 6 weeks of double-blind therapy with either valsartan (80 mg), hydrochlorothiazide (HCTZ) (25 mg), or placebo once daily. Basal NO production and release was assessed by measuring forearm blood flow (FBF) in response to intra-arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA), and endothelium-dependent vasodilation by measuring FBF in response to intra-arterial administration of acetylcholine, respectively. Intra-arterial infusion of noradrenaline and sodium nitroprusside was used to assess endothelium-independent changes in FBF. Blood pressure (BP) similarly decreased with active treatments (P < .001). After valsartan treatment, the decrease of FBF in response to L-NMMA was augmented (4 micromol/min L-NMMA, -1.3 +/- 1.2 after v -0.5 +/- 1.1 mL/min/100 mL before therapy, P < .02; 8 micromol/min L-NMMA: -1.7 +/- 1.3 after v -1.1 +/- 1.2 mL/min 100 mL before therapy, P < .05). No improvement was found after placebo or HCTZ treatment. Changes in L-NMMA-induced decrease of FBF with valsartan treatment were not related to BP changes. Neither drug substantially modified the response of FBF induced by intra-arterial infusion of acetylcholine, noradrenaline, and sodium nitroprusside. CONCLUSIONS: The AT(1) receptor blockade with valsartan improved basal NO production and release. The effect seems to be BP independent, as BP reduction with HCTZ failed to increase NO availability.     

The effect of the phytoestrogen genistein on plasma nitric oxide concentrations,endothelin-1 levels and endothelium dependent vasodilation in postmenopausal women

The phytoestrogen genistein improves endothelial dysfunction in ovariectomized rats through a nitric oxide-dependent mechanism. We investigated whether genistein alters the balance between the nitric oxide products and endothelin-1 and influences endothelium-dependent vasodilation in postmenopausal women. Sixty healthy postmenopausal women were enrolled in the study. A double-blind, placebo controlled, randomized design was employed. After a 4-week stabilization on a standard fat-reduced diet, participants to the study were randomly assigned to receive either genistein (n=30; 54 mg/day) or placebo (n=30). Flow-mediated, endothelium-dependent vasodilation of the brachial artery, plasma nitric oxide breakdown products and endothelin-1 levels were measured at baseline and after 6 months of genistein therapy. The mean baseline level of nitrites/nitrates was 22+/-10 micromol/l and increased to 41+/-10 micromol/ml after 6 months of treatment. The mean baseline plasma endothelin-1 level was 14+/-4 pg/ml and decreased to 7+/-1 pg/ml following 6 months of treatment with genistein. The mean baseline ratio of nitric oxide to endothelin also significantly increased at the end of treatment. Flow-mediated, endothelium-dependent vasodilation of the brachial artery was 3.9+/-0.8 mm at baseline and increased to 4.4+/-0.7 mm after 6 months of treatment. Placebo-treated women showed no changes in plasma nitrites/nitrates, endothelin-1 levels and flow-mediated vasodilation. Genistein therapy improves flow-mediated endothelium dependent vasodilation in healthy postmenopausal women. This improvement may be mediated by a direct effect of genistein on the vascular function and could be the result of an increased ratio of nitric oxide to endothelin.     

Oxidized LDL and small LDL particle size are independently predictive of a selective defect in microcirculatory endothelial function in type 2 diabetes

AIM: To explore the associations of LDL (low-density lipoprotein) particle size and oxidized LDL with endothelium-dependent function of the forearm microcirculation in diabetes. METHODS: Endothelium-dependent function was examined in 43 middle-aged men and women with type 2 diabetes and 10 age-matched controls. All received aspirin to inhibit endothelial cyclo-oxygenase. Forearm blood flow (FBF) was measured using venous occlusion plethysmography with separate administration of acetylcholine (ACh) and bradykinin (BK) into the brachial artery. Endothelium-independent function was assessed using sodium nitroprusside (SNP). N(G)-monomethyl-L-arginine (L-NMMA) was co-infused with ACh (ACh + L-NMMA) and BK (BK + L-NMMA) to assess non-NO-mediated contributions to endothelium-dependent function. RESULTS: Subjects with diabetes had impaired endothelium-dependent and endothelium-independent function compared with controls (p < 0.01 for ACh, BK and SNP). In multivariate regression analysis, LDL size (r = 0.41 and p = 0.007), oxidized LDL (r = -0.41 and p = 0.007) and duration of diabetes (r = -0.37 and p = 0.02) predicted FBF response to ACh independently of age, gender and systolic blood pressure. There were no associations between LDL size, oxidized LDL, duration of diabetes and FBF response to BK, SNP, ACh + L-NMMA or BK + L-NMMA. CONCLUSION: In type 2 diabetes, small dense LDL particles, duration of diabetes and oxidized LDL may independently contribute to endothelial dysfunction of the microcirculation. These disturbances may occur via a selective defect, because ACh and BK activate endothelial NO synthase via different G-protein signal transduction pathways.     

Asymmetric dimethylarginine, L-arginine, and endothelial dysfunction in essential hypertension

OBJECTIVES: We investigated the relationship between ADMA plasma levels and endothelium-dependent vasodilation in 36 never-treated essential hypertensives and in 8 normotensive healthy subjects. BACKGROUND: It has been demonstrated that endothelium-dependent vasodilatation is impaired in essential hypertension. The potential contribution of asymmetric dimethylarginine (ADMA) to endothelial dysfunction of hypertensive humans has received poor attention. METHODS: Endothelial function was measured during intra-arterial infusion of acetylcholine (ACh), alone and during co-infusion of L-arginine, and sodium nitroprusside at increasing doses. Concentrations of ADMA and L-arginine in plasma were measured by high-performance liquid chromatography. RESULTS: Hypertensive subjects had significantly higher ADMA and L-arginine plasma concentrations than normotensive healthy controls; ACh-stimulated forearm blood flow (FBF) was significantly reduced in hypertensive subjects in comparison to normotensive control subjects (p < 0.0001). Intra-arterial coinfusion of L-arginine induced a further significant enhancement in ACh-stimulated vasodilation in hypertensive patients. In these, ADMA was strongly and inversely associated with the peak increase in FBF. In a multivariate model, only ADMA and L-arginine were independent correlates, accounting for 33.9% and 8.9% of the variability in the peak FBF response to ACh (p < 0.0001), respectively. CONCLUSIONS: The main finding in this study is that in essential hypertensives the L-arginine and endogenous inhibitor of nitric oxide synthase, ADMA, are inversely related to endothelial function.     

Endothelium-derived relaxing factor inhibits hypoxic pulmonary vasoconstriction in rats

The hypothesis that endothelium-derived relaxing factor (EDRF) modulates hypoxic pulmonary vasoconstriction (HPV) was tested in isolated, blood-perfused rat lungs ventilated with gas mixtures of 21% O2-5% CO2-74% N2 (normoxia) or of 3% O2-5% CO2-92% N2 (hypoxia); 30 microM NG-monomethyl-L-arginine (L-NMMA), an inhibitor of EDRF production, caused a reduction in the endothelium-dependent relaxant response to acetylcholine (ACh) from 62 +/- 7, 88 +/- 4, and 100 +/- 4% to 26 +/- 8, 49 +/- 12, and 75 +/- 7% at ACh concentrations of 1, 10, and 100 microM, respectively (p less than 0.05 at all concentrations), indicating that L-NMMA acts via the inhibition of EDRF production. L-NMMA induced a concentration-related augmentation in HPV of 20 +/- 5, 32 +/- 8, and 34 +/- 8% at concentrations of 30, 300, and 1,000 microM (p less than 0.05, compared with a vehicle control group at all concentrations). The pressor response to a dose of angiotensin II (A-II), which produced the same increase in pulmonary artery pressure as that induced by hypoxia, was also significantly augmented (2 +/- 0.6%), but to a lesser extent. The augmentation of HPV by 30 microM L-NMMA was completely reversed by 1 mM L-arginine (a precursor of EDRF), but not by D-arginine (an isomer of L-arginine). One and 6 mM L-arginine, but not 6 mM D-arginine caused a significant inhibition of HPV by 20 +/- 2 and 47 +/- 12% (p less than 0.05, compared with the vehicle control group) and a small but not significant reduction in A-II-mediated contraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Calcium antagonist isradipine improves abnormal endothelium-dependent vasodilation in never treated hypertensive patients.

OBJECTIVE: To examine whether middle (two months) and long-term (six months) isradipine sustained-release treatment improves endothelium-dependent vasodilation in never treated hypertensive patients. METHODS: The responses of the forearm vasculature to acetylcholine (7.5, 15 and 30 micrograms/min) and sodium nitroprusside (0.8, 1.6, 3.2 micrograms/min) were evaluated in 12 normotensive controls (seven men and five women, aged 25 to 49 years), and in 12 hypertensives (eight men and four women, aged 20 to 47 years) at baseline and after two and six months of isradipine sustained-release treatment. Drugs were infused into the brachial artery, and forearm blood flow was measured by strain-gauge plethysmography. RESULTS: At baseline, the response to acetylcholine was significantly lower in hypertensives vs controls: at the highest dose (30 micrograms/min), forearm blood flow was 28.6 +/- 2.4 ml/100 ml of tissue per min in the controls vs 8.9 +/- 1.0 ml/100 ml of tissue per min in hypertensive (p < 0.0001). Similarly, vascular resistance was significantly (p < 0.0001) higher in hypertensives: 4.8 +/- 0.5 units (controls) vs 15.1 +/- 1.7 units (hypertensives). After isradipine treatment, the forearm blood flow in hypertensive patients changed from 8.9 +/- 1.0 ml/100 ml of tissue per min to 16.0 +/- 1.2 ml/100 ml of tissue per min (two months; p < 0.0001) and 15.2 +/- 1.4 ml/100 ml of tissue per min (six months; p < 0.0001). Isradipine treatment did not modify the vasodilating effect of sodium nitroprusside. CONCLUSIONS: Our data demonstrate for the first time that the calcium antagonist isradipine improves acetylcholine-induced vasodilation in hypertensives.